gpio lcd display factory
I needed a display for a new project that I am working on and saw that the 3.5 RPI Display Board was on sale and decided to pick one up. I"ve previously used mini OLED displays before, but they"re pretty limited by its size and the colors that it can display. This is a 480x320 resolution device that is designed to affix right onto the Raspberry Pi (RPi) GPIO pins. The installation is simple as you"d imagine:
For the project I had in mind, I do not need a fancy GUI nor the use of the touch controller. The display will be used to show console statistics and accessing the device using SSH.
I am using a vanilla Raspbian lite and no additional drivers were required to get this working. All we need to do is configure some boot scripts and introduce some new configuration files. It"s possible to do this manually, but thankfully LCD-Show automates the process for us.
It would have been nice if I could have mirrored the HDMI output and the LCD panel at the same time, but I could not figure out how to do this or if it was possible at all.
Secondly, it allows a remote user to connect to an existing SSH session. If I were to kick off a Tmux session on user log on, I am be able to connect to the same session from a remote computer. This means that I should connect to the session that is being shown on the physical display and interact with it as if I was seated in front of it.
The LCD is compatible with both the Raspberry PI Zero and its big brother variants so these same instructions can be applied to get them both running.
LCD character displays are useful for displaying information without the need for an external monitor. Common LCD character displays can be connected directly to the GPIO pins, but such an approach requires the use of up to 10 GPIO pins. For scenarios that require connecting to a combination of devices, devoting so much of the GPIO header to a character display is often impractical.
Many manufacturers sell 20x4 LCD character displays with an integrated GPIO expander. The character display connects directly to the GPIO expander, which then connects to the Raspberry Pi via the Inter-Integrated Circuit (I2C) serial protocol.
There are many manufacturers of LCD character displays. Most designs are identical, and the manufacturer shouldn"t make any difference to the functionality. For reference, this tutorial was developed with the SunFounder LCD2004.
The device address for the GPIO expander depends on the chip used by the manufacturer. GPIO expanders equipped with a PCF8574 use the address 0x27, while those using PCF8574A chips use 0x3F. Consult your LCD"s documentation.
Another using declaration creates an instance of Lcd2004 to represent the display. Several parameters are passed to the constructor describing the settings to use to communicate with the GPIO expander. The GPIO expander is passed as the controller parameter.
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p6 rootfstype=ext4 elevator=deadline rootwait fbtft_device.custom fbtft_device.name=waveshare32b fbtft_device.gpios=dc:22,reset:27 fbtft_device.bgr=1 fbtft_device.speed=48000000 fbcon=map:10 fbcon=font:ProFont6x11 logo.nologo dma.dmachans=0x7f35 console=tty1 consoleblank=0 fbtft_device.fps=50 fbtft_device.rotate=0
Unfortunately, their “driver” is an SD card image containing a complete installation of Raspbian which has been preconfigured to use their display. Which is fine if you’re setting up a brand new system that doesn’t need to be a specific distro, but if you’re trying to add the display to an existing Raspberry Pi, already configured the way you want it, with software installed and data present, or if you want to use a specific distro such as Octopi, then it’s not terribly helpful.
Hello..I tired to interface this lcd “https://www.crazypi.com/raspberry-pi-products/Raspberry-Pi-Accessories/32-TOUCH-DISPLAY-RASPBERRY-PI” to my Raspberry pi model B+.I got a DVD containing image for LCD in the package.I burned it to the SD card and plugged in the display.But my lcd is completly blank.But green inidcation led (ACT LED) in board is blinking.Why my LCD is Blank ?
My Touchscreen is now working fine.The problem was for the ribbon cable on the back side of LCD.It was not connected properly.I just tighted the cable and it worked fine.Hope it will be useful tip.
Just got my Pi2 running Wheezy, working with the Eleduino 3.5 LCD without running the OEMs image… kinda. I didn’t want to rebuild the application environment again, so was avoiding flashing the SD.
[ 0.000000] Kernel command line: dma.dmachans=0x7f35 bcm2708_fb.fbwidth=656 bcm2708_fb.fbheight=416 bcm2709.boardrev=0xa21041 bcm2709.serial=0x631a4eae smsc95xx.macaddr=B8:27:EB:1A:4E:AE bcm2708_fb.fbswap=1 bcm2709.disk_led_gpio=47 bcm2709.disk_led_active_low=0 sdhci-bcm2708.emmc_clock_freq=250000000 vc_mem.mem_base=0x3dc00000 vc_mem.mem_size=0x3f000000 dwc_otg.lpm_enable=0 console=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait fbtft_device.custom fbtft_device.name=flexfb fbtft_device.gpios=dc:22,reset:27 fbtft_device.bgr=1 fbtft_device.speed=48000000 fbcon=map:10 fbcon=font:ProFont6x11 logo.nologo dma.dmachans=0x7f35 console=tty1 consoleblank=0 fbtft_device.fps=50 fbtft_device.rotate=0
thank you for your great tutorial, it got me on the right way. unfortunataly i only see some boot messages on the lcd and then it turns black. maybe you could give me a hint on how to get it working entirely.
i have a watterott display (https://github.com/watterott/RPi-Display) and changed the device-name to “rpi-display”. i use a rsapberrypi 2 and hae the latest raspian image installed.
I too have a raspberry pi 2, and a waveshare spotpear 3.2 RPi lcd (v3) and I just can’t get it to work! I suspect I have a faulty LCD, but thought I’ll try this forum for help before I sent it back.
Soon as the pi is powered, the LCD lights up all white, with a few vertical pixels coloured at one of the edges, and nothing else. I don’t think that should happen – not at least before the BOIS has started up.
It seems all appears to be working – just the LCD is still all white with a single line of coloured pixels on edge) and nothing else. Is there a way to output, like jeff G script, of touch points?
I had the same one, I finally found a driver for it here: http://www.waveshare.net/wiki/3.2inch_RPi_LCD_(B) you will need to translate the page, but unpack the driver then run sudo ./LCD-show/LCD32-show. It should reboot and all will be good with the screen :)
My system: Raspberry Pi 2 Model B with Raspian Wheezy from Febuary 2015. LCD display of Sainsmart 3.2 http://www.conrad.de/ce/de/product/1283498/Raspberry-Pi-Display-Modul-Touch-Display-81-cm-32/?ref=home&rt=home&rb=1
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 cgroup_enable=memory elevator=deadline rootwait fbtft_device.custom fbtft_device.name=sainsmart32_spi fbtft_device.gpios=dc:24,reset:25 fbtft_device.bgr=1 fbtft_device.speed=48000000 fbcon=map:10 fbcon=font:ProFont6x11 logo.nologo dma.dmachans=0x7f35 console=tty1 consoleblank=0 fbtft_device.fps=50 fbtft_device.rotate=90
ads7846_device model=7846 cs=1 gpio_pendown=23 speed=2000000 keep_vref_on=1 swap_xy=1 pressure_max=255 x_plate_ohms=60 x_min=300 x_max=3800 y_min=700 y_max=3400
The LCD display shows the raspberry correctly. However, the touch screen input does not work. The mouse pointer can I move correctly with your finger, but I can not select things (function of the left mouse button).
Do not follow this article when you don’t know what kind of LCD module. In my case, I follow all of this and my raspberry pi cannot boot anymore. I will try to recover, but I think I should format my SD card and reinstall OS.
Expecting this would builtin driver module within kernel and help with avoiding mistakenly overwriting anything. But with this is cause LCD screen to go blank white and no boot activity. Also noticed on HDMI it get stuck on Initial rainbow screen and stuck on that.
Does anyone tried splash boot screen with waveshare v4 LCD and Rpi2? I tried to follow some example from https://github.com/notro/fbtft/wiki/Bootsplash but no success.
Great tutorial thanks; got an X session working great 1st time. Has anybody managed to get Kodi/XMBC working on the LCD either Kodi standalone, Raspbmc or Xbian?
fbtft_device name=waveshare32b gpios=dc:22,reset:27 speed=48000000 width=320 height=240 buswidth=8 init=-1,0xCB,0x39,0x2C,0x00,0x34,0x02,-1,0xCF,0x00,0XC1,0X30,-1,0xE8,0x85,0x00,0x78,-1,0xEA,0x00,0x00,-1,0xED,0x64,0x03,0X12,0X81,-1,0xF7,0x20,-1,0xC0,0x23,-1,0xC1,0x10,-1,0xC5,0x3e,0x28,-1,0xC7,0x86,-1,0×36,0x28,-1,0x3A,0x55,-1,0xB1,0x00,0x18,-1,0xB6,0x08,0x82,0x27,-1,0xF2,0x00,-1,0×26,0x01,-1,0xE0,0x0F,0x31,0x2B,0x0C,0x0E,0x08,0x4E,0xF1,0x37,0x07,0x10,0x03,0x0E,0x09,0x00,-1,0XE1,0x00,0x0E,0x14,0x03,0x11,0x07,0x31,0xC1,0x48,0x08,0x0F,0x0C,0x31,0x36,0x0F,-1,0×11,-2,120,-1,0×29,-1,0x2c,-3
ads7846_device model=7846 cs=1 gpio_pendown=17 speed=1000000 keep_vref_on=1 swap_xy=0 pressure_max=255 x_plate_ohms=60 x_min=200 x_max=3900 y_min=200 y_max=3900
The reason I did this was because on a production version of my system I added the 3.2 screen and it worked great except for the x-axis. So I wanted to see if there was something in my system that was interfering or if this is another error. Now with a raw rasping the driver does not work at all. I wonder if the touch pin has changed since the kernel is using BCM pins instead of GPIO pin numbers?
I have exactly the same problem. I also installed a new version of Raspbian, and the LCD part works fine (except all the windows are way too large), but the touch part doesn’t work at all… I’m using Waveshare Spotpear 3.2″ V4.
I remember that I plugged in the screen wrongly one time, before configuring any of the GPIO pins. Can this have damaged the screen? Still it’s weird that the display part works well and the touch part not at all.
I am trying to use the sainsmart 2.8″ lcd sold through microcenter, using the sainsmart32_spi … seems to have the same pinouts, should I be able to get this to work? I am stuck at the white out screen on the lcd, doesn’t seem to recognize the module either.
Unfortunately I’ve tried that ( a few times actually) but the file still doesn’t exist. Thanks very much for the assistance anyway. I must be doing something wrong. My Raspian came from a Noobs installation, I’m wondering if I should try installing the OS from somewhere else. My LCD screen didn’t come with a CD or any docs so I’m completely in the dark here.
Well figured out that step 1 was causing my problems. I’m guessing it is shutting off my hdmi feed and trying to switch it over to the SPI, am I guessing right? If so, not sure how I’m suppose to complete the rest of the steps if my hdmi output gets turned off before the LCD is actually set up to work…that sounds kind of smartass-like, which is not my intention, just looking for some clarification on what is going on in that first step as I am fairly new to this stuff. Thanks.
Anyway, I was able to do the rest of the steps with no problem. LCD didn’t work, but I am using a Waveshare 3.5, which doesn’t look to be supported yet. Mostly I am trying to play around and see if I can get it working somehow. Anyone found a way to do this yet?
Here is a link to an updated image from waveshare. Upon install it got the display up and running, but I still do not have touch functionality. I’ve been playing around with it, but it has been to no avail…hopefully someone better at this stuff from me can get the touch working.
I am having an issue with getting the GUI back. Every time I use startx my pi just sits there for about two minutes saying “No protocol specified”, and then it just gives up. I went through this tutorial about four times now and am not certain why it is doing this. I have the exact same LCD as is in the tutotial (WaveShare 3.2b). any help would be great.
Thanks for the tutorial. It works, but I get the boot/command line stuff on the HDMI monitor and the LCD only comes on when I do startx. Is there a way to get everything to appear on the LCD screen?
Now the OS freezes at the emulation station loading screen, and if I connect my lcd it gives me a lot of error messages which I can only see on the 3.2 inch screen.
This was an excellent tutorial. I have gotten an output to the screen, but no touchscreen usage . I have the Waveshare SpotPear 3.2 Inch LCD V4 screen, but using Raspberry PI 2 with wheezy. Any ideas?
I actually used the driver from here http://www.waveshare.com/wiki/3.2inch_RPi_LCD_(B) , from a new wheezy build, did nothing except enable SPI in config, install driver, and change mmcblk0p2 to mmcblk0p6 in cmdline.txt and it all worked, no drama.
i have raspberry pi 2 with 3.2 inch rpi lcd v4 waveshare spotpear.i have done as per your instructions.the display is working but touch screen not working.error shows waveshare32b module not found as well as touch screen module not found messages.
Unfortunately I have lost the Touch facility on my Waveshare 3.5″ LCD Touchscreen? Can you offer any reasons as to why? I copied the Raspbian image to my Raspberry Pi from the Waveshare website first of all. The Touchscreen displays but is not reactive with any touch
I have purchased a raspberry pi B+ total kit and waveshare 3.2 TFT display online. In the package i have been given a pre-loaded NOOBS installed SD card. I did not even start anything yet. What should i do what r the things needed and how to connect the display i really want to know. I need help as i don’t know anything. Does the above solution help or will u suggest something………………..
Hi great article thanks. I am trying to get a waveshare 7 inch LCD with capacitive touch running it works with the suppled image but if you upgrade it breaks the capacitive touch. I have a sense-hat and GPS which require the latest kernel and RASPIAN image and the install program for the screen replaces the /lib/modules directory and the kernel with older ones. I need to be able to install the touch drivers into a new clean OS can anyone give me some pointers? Thanks
So I have the original image that came with my screen and it works fine with the LCD but my problem is that I want to use my LCD screen with other distros (at this time I am trying to use it with Kali Linux with TFT support by default https://www.offensive-security.com/kali-linux-vmware-arm-image-download/) What do I have to do to transfer the needed files from the original image that WORKS with the screen and use them with another image?
I originally bought this bundle http://www.amazon.com/gp/product/B013E0IJUK?psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s00 with an RPi LCD V3 and no extra documentation on the specifics on the chipset. I tried with the bftft drivers but since I have no idea what to call this screen I just suppose it isn’t supported.
I am using the same LCD and followed your tutorial. Have your tested the guide lately? Are you certain that it works? I see the boot messages on console but I get white screen as GUI starts.
I have tried to set up waveshare 32b on my Pi B using the latest Raspian download. I learned a lot in the process using Windows Putty, Nano etc. I have repeated the setup process several times from scratch and included the corrections for possible overwriting. My Waveshare SpotPear 3.2 inch RPi LCD V4 just shows a white screen. Any suggestions?
Hi, I am using raspberry pi 2 with raspbian jessie installed. I the waveshare spotpear 3.2 v4. The above instructions are not working. and after completing the steps there was no display from hdmi or lcd. One things to notify is.: the etc/modules files only had i2c-dev and not snd-bcm2835.
I am trying to get this to work with Retro Pie 3.3.1 and the Waveshare3.2″ v4 but I only get the terminal on the lcd and emulation station starts on hdmi. to get it working with retro pie i just replaced startx with emulationstation. how do i get this to work?
Sir, Your post has very useful to me. i am using Tinylcd. but i cant get display. i am performing all the steps in your post. i cant get touch controller information from the product website and also i am using RASPberryPi B+ model. could u please give me best solution to my work. Than you.
i installed android OS in raspberry pi 2. can i use same LCD touch screen set up for android installed raspberry pi 2 which you are used for raspbian.
Is it normal the white back light during the whole process of initializing (I suspect that during the transportation trere is a deffect)? The problem is that I missed the step #1 and I performed it at the end. Unfortunately I don’t have any monitor available right now – neither “normal”, neither LCD :))))). Is it possible turning back the system or the only option is reinstallation of the Raspbian?
I’m trying to use an original Raspberry Pi model B with a cheap 3.5 inch 320×480 LCD which allegedly was manufactured to work with the Pi and has the correct fittings to fit over the GPIO pins. The operating system is the latest, downloaded yesterday and installed with NOOBS. I can’t get past step 2 of this guidance. When I reboot after using raspi-config I can see text generated as the Pi boots, then the HDMI fed screen goes blank apart from a flashing cursor in the top left hand corner. The LCD just remains white with nothing else on it. I have missed out step 1 and rebooted after step 2 and the screen functions as I would expect. Does anyone have any ideas please?
Thanks for the great tutorial. I do have a question. Once you install the drivers for the lcd are you effectively disabiling the hdmi port or is it still available to use and will the pi function with both displays. I have a pi 3
once you install the drivers it replaces the kernel by disabling hdmi output and enables it for LCD. i don’t think we have a solution to get em both working at the same time. ( you are encouraged to search for it )
i am sorry, but i am a naive , and i have this question, can we upload any file into it for the display? like have a software in which if i tap it gives back a feedback to the code?
ads7846_device model=7846 cs=1 gpio_pendown=17 speed=1000000 keep_vref_on=1 swap_xy=0 pressure_max=255 x_plate_ohms=60 x_min=200 x_max=3900 y_min=200 y_max=3900
I’d like to find the driver software for my 7″ LCD with touch (official Pi unit) so that I can use it in buildroot. I wanted to make sure this kernel is the one before I started digging further.
I started through your tutorial and completed step 3 and rebooted. After the Raspberry screen and some of the boot text on my HDMI monitor, I now have a black HDMI monitor and a white screen on my LCD. Does this mean that the bootloader was overwritten or something else is wrong? How am I supposed to enter in the proposed fixes to the bootloader, when I can’t get the RPi to boot? Do I have to interrupt the boot process at some point to reinstall the bootloader or what?
Its a script. Download and instead of running sudo ./LCD4-show run cat ./LCD4-show to simply display what it does without actually running it. The commands are fairly simple modifying a few files. I actually saved the LCD-show.tar.gz on my own server for faster future download but also for backup as it saved me tons of hours (if that’s a measuring unit for time :) )
I used this link though (smaller file ~ 50 KB, fast download) http://www.waveshare.com/w/upload/4/4b/LCD-show-161112.tar.gz and replaced LCD4-show with LCD32-show in the last line.
i bought a 3.5 inch tft lcd screen from banggood. and i have installed raspian jessie, the latest version, in my sd card. but when i power on my Pi, only a white backlit screen comes. there are no images or graphics whatsoever.
PLEASE DELETE this article. You have great power with this article showing up for so many people in their search results, and you display ZERO responsibility. This is terrible!
Will your system work with my SainSmart 2.8″ 2.8 inch TFT LCD 240×320 Arduino DUE MEGA2560 R3 Raspberry Pi ? I would like to know before not be able to back out. Thanks, Lee
I ‘m actually using a LCD Waveshare3.2” , I followed your steps to setup the lcd touchscreen for my rpi and it work but I have a problem with the resolution because if I open a repertory I do not see the whole contents on the screen .
hi! thank you for this post…. I was wondering if all the raspberry pi’s gpio are being held by this screen or do we have any of those availables for use??
it worked. but the resolution is for bigger screens. i got the menubar small, but the rest appears too big , and out of screen. the wastebasket icon is 1/6 of my 3.2″ screen. wich HAS the resolution capability too display the whole desktop. But i’m a PI newby and dunno how to adjust the screen resolution on this display. anybody?
I did a 5inch LCD for my raspberry pi. I dont use the touchscreen so i didnt have to install any drivers. It works out of the box but doesnt cover the whole screen unless you open the terminal and do:
In the case of the WaveShare driver, their setup script from their “LCD_show” repository will copy a device-tree overlay to /boot/overlays/ that provides most of the module config etc via boot-time device-tree patch.
Interfacing a Touchscreen LCD with a Raspberry Pi is very useful as this setup can be used to develop Raspberry Pi based stand-alone systems like Weather Monitoring Stations, Security Systems, and Camera Interfacing etc. Adding a Touchscreen to your Raspberry Pi opens up doors to a lot of projects as well as increases the portability of the system.
Having a nice LCD Display on your Raspberry Pi can allow us to make complex projects like a media center, personal computer, smart phone, tablet, etc.
There are different types of Touchscreen LCDs available in the market today for Raspberry Pi from different manufacturers with different screen sizes, resolutions, operable with stylus, etc.
In this project, we will see how to setup an LCD Touchscreen on Raspberry Pi. For this project, we have chosen a WaveShare SpotPear 3.2 inch RPi LCD V4 touchscreen type LCD display.
NOTE: We’ll show you how to setup WaveShare 3.2 inch LCD with Raspberry Pi using the official drivers and also the provided Raspbian image. We tried to install this using our own Raspbian Jessie and Drivers but there were some problems. We will definitely update how to install any type of LCD with Raspberry Pi very soon.
There are different manufacturers of Touchscreen LCD displays for Raspberry Pi like Adafruit, Newhaven Display, Haoyu, Freetronics, WaveShare, Watterott Electronics and many more but we thought Touchscreen LCD displays from WaveShare for Raspberry Pi are affordable, easy to use and comes with drivers and their own version of Raspbian OS (our thoughts and might differ with other users).
There are many variants of Touchscreen LCDs from WaveShare like 2.8 inch, 3.2 inch, 3.5 inch, 5 inch, 7 inch, 10.1 inch etc. For setting up an LCD Touchscreen with Raspberry Pi, we are going to use a 3.2 Inch WaveShare SpotPear LCD.
This particular LCD Display has a Resistive Touchscreen with a screen resolution of 320×240. It is interfaced to Raspberry Pi using SPI protocol. The LCD module has 3 user button that can be programmed to do additional functions.
The Wave Share 3.2 inch display can be directly plugged in to the Raspberry Pi on the GPIO Pins. It uses 26 Pins of the available 40 pins of the Raspberry Pi’s GPIO. Out of the 26 pins used, some do not have any connections (NC – No Connection).
First we will see the Pinout of the Raspberry Pi GPIO and then we will see the relevant pins required to connect LCD using SPI. The following image shows the pin out of Raspberry Pi’s GPIO Pins.
In these 40 pins, the connector on the back of the WaveShare 3.2 inch LCD has 26 pins (2 rows with 13 pins in each). The following table gives the list of pins we are going to need to interface the LCD with Raspberry Pi.
Now that we have seen the basic information about the WaveShare Touchscreen LCD module, we will proceed with the setup. There are two ways you can setup the LCD: 1. Use your own OS (Raspbian) and install the drivers or 2. Use the provided OS image file (it can also be downloaded) and do a fresh install of the OS.
If you want to test whether the LCD is working or not, you can go with the OS image provided by the manufacturer of the LCD. It is usually given in a CD or can be downloaded from the official website.
Write this image file on to the microSD card, insert it into Raspberry Pi and boot the Pi with LCD inserted on the Raspberry Pi. The Raspberry Pi directly enable the Touchscreen LCD display.
But, if we want to use our Raspberry Pi with any OS of our choice, like Raspbian Jessie for example, first thing we need to do is download the drivers for the LCD Module from the website.
You can also download the image file from this site. There are two versions of drivers in the website. We have downloaded the first one (LCD-show-170703.tar.gz) and put it in the Desktop. Do not unzip or unrar it.
On the left side, go to the folder where you have downloaded the LCD Driver file. In our case, it is located on the Desktop. On the right side, go to home/pi folder. Drag and drop the LCD Driver File from left side to right side.
Now, open Putty and login in to Raspberry Pi. After logging in successfully, we need to extract the contents of the LCD Driver file. To see the list of files and directories, you can enter the following command and press enter.
Now, to extract the contents, enter the following command. This command will extract the contents of the file LCD-show-170703-tar-gz to the present folder.
A new folder with name “LCD-show” will be created in the process. We need to go in to that directory. For that type the following command and hit enter.
Now, since our WaveShare LCD Module is a 3.2 inch one, we need to install the drivers specific for this LCD Module. For that, enter the following commands one after the other.
After entering the above commands, the installation of the LCD Touchscreen drivers will be initialised and the Raspberry Pi will automatically reboot. If not, you reboot the Raspberry Pi and after booting up, the Raspberry Pi will directly display on the LCD.
I"m currently trying to show "Hello World" on 16x2 LCD display which I have already connected to the breadboard, which is connecting to Raspberry Pi with Windows 10 IoT Core. I have searched libraries that might be able to handle. I found RaspberryPiDotNet Library but it is not compatible with UWP as it seems.
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In these videos, the SPI (GPIO) bus is referred to being the bottleneck. SPI based displays update over a serial data bus, transmitting one bit per clock cycle on the bus. A 320x240x16bpp display hence requires a SPI bus clock rate of 73.728MHz to achieve a full 60fps refresh frequency. Not many SPI LCD controllers can communicate this fast in practice, but are constrained to e.g. a 16-50MHz SPI bus clock speed, capping the maximum update rate significantly. Can we do anything about this?
The fbcp-ili9341 project started out as a display driver for the Adafruit 2.8" 320x240 TFT w/ Touch screen for Raspberry Pi display that utilizes the ILI9341 controller. On that display, fbcp-ili9341 can achieve a 60fps update rate, depending on the content that is being displayed. Check out these videos for examples of the driver in action:
Given that the SPI bus can be so constrained on bandwidth, how come fbcp-ili9341 seems to be able to update at up to 60fps? The way this is achieved is by what could be called adaptive display stream updates. Instead of uploading each pixel at each display refresh cycle, only the actually changed pixels on screen are submitted to the display. This is doable because the ILI9341 controller, as many other popular controllers, have communication interface functions that allow specifying partial screen updates, down to subrectangles or even individual pixel levels. This allows beating the bandwidth limit: for example in Quake, even though it is a fast pacing game, on average only about 46% of all pixels on screen change each rendered frame. Some parts, such as the UI stay practically constant across multiple frames.
Good old interlacing is added into the mix: if the amount of pixels that needs updating is detected to be too much that the SPI bus cannot handle it, the driver adaptively resorts to doing an interlaced update, uploading even and odd scanlines at subsequent frames. Once the number of pending pixels to write returns to manageable amounts, progressive updating is resumed. This effectively doubles the maximum display update rate. (If you do not like the visual appearance that interlacing causes, it is easy to disable this by uncommenting the line #define NO_INTERLACING in file config.h)
A number of other micro-optimization techniques are used, such as batch updating rectangular spans of pixels, merging disjoint-but-close spans of pixels on the same scanline, and latching Column and Page End Addresses to bottom-right corner of the display to be able to cut CASET and PASET messages in mid-communication.
If you have been running existing fbcp driver, make sure to remove that e.g. via a sudo pkill fbcp first (while running in SSH prompt or connected to a HDMI display), these two cannot run at the same time. If /etc/rc.local or /etc/init.d contains an entry to start up fbcp at boot, that directive should be deleted.
When using one of the displays that stack on top of the Pi that are already recognized by fbcp-ili9341, you don"t need to specify the GPIO pin assignments, but fbcp-ili9341 code already has those. Pass one of the following CMake directives for the hats:
-DPIRATE_AUDIO_ST7789_HAT=ON: If specified, targets a Pirate Audio 240x240, 1.3inch IPS LCD display HAT for Raspberry Pi with ST7789 display controller
-DKEDEI_V63_MPI3501=ON: If specified, targets a KeDei 3.5 inch SPI TFTLCD 480*320 16bit/18bit version 6.3 2018/4/9 display with MPI3501 display controller.
If you connected wires directly on the Pi instead of using a Hat from the above list, you will need to use the configuration directives below. In addition to specifying the display, you will also need to tell fbcp-ili9341 which GPIO pins you wired the connections to. To configure the display controller, pass one of:
-DILI9341=ON: If you are running on any other generic ILI9341 display, or on Waveshare32b display that is standalone and not on the FreeplayTech CM3/Zero device, pass this flag.
-DILI9340=ON: If you have a ILI9340 display, pass this directive. ILI9340 and ILI9341 chipsets are very similar, but ILI9340 doesn"t support all of the features on ILI9341 and they will be disabled or downgraded.
-DILI9486L=ON: If you have a ILI9486L display, pass this directive. Note that ILI9486 and ILI9486L are quite different, mutually incompatible controller chips, so be careful here identifying which one you have. (or just try both, should not break if you misidentified)
-DGPIO_TFT_DATA_CONTROL=number: Specifies/overrides which GPIO pin to use for the Data/Control (DC) line on the 4-wire SPI communication. This pin number is specified in BCM pin numbers. If you have a 3-wire SPI display that does not have a Data/Control line, set this value to -1, i.e. -DGPIO_TFT_DATA_CONTROL=-1 to tell fbcp-ili9341 to target 3-wire ("9-bit") SPI communication.
-DGPIO_TFT_RESET_PIN=number: Specifies/overrides which GPIO pin to use for the display Reset line. This pin number is specified in BCM pin numbers. If omitted, it is assumed that the display does not have a Reset pin, and is always on.
-DGPIO_TFT_BACKLIGHT=number: Specifies/overrides which GPIO pin to use for the display backlight line. This pin number is specified in BCM pin numbers. If omitted, it is assumed that the display does not have a GPIO-controlled backlight pin, and is always on. If setting this, also see the #define BACKLIGHT_CONTROL option in config.h.
fbcp-ili9341 always uses the hardware SPI0 port, so the MISO, MOSI, CLK and CE0 pins are always the same and cannot be changed. The MISO pin is actually not used (at the moment at least), so you can just skip connecting that one. If your display is a rogue one that ignores the chip enable line, you can omit connecting that as well, or might also be able to get away by connecting that to ground if you are hard pressed to simplify wiring (depending on the display).
To get good performance out of the displays, you will drive the displays far out above the rated speed specs (the rated specs yield about ~10fps depending on display). Due to this, you will need to explicitly configure the target speed you want to drive the display at, because due to manufacturing variances each display copy reaches a different maximum speed. There is no "default speed" that fbcp-ili9341 would use. Setting the speed is done via the option
-DSPI_BUS_CLOCK_DIVISOR=even_number: Sets the clock divisor number which along with the Pi core_freq= option in /boot/config.txt specifies the overall speed that the display SPI communication bus is driven at. SPI_frequency = core_freq/divisor. SPI_BUS_CLOCK_DIVISOR must be an even number. Default Pi 3B and Zero W core_freq is 400MHz, and generally a value -DSPI_BUS_CLOCK_DIVISOR=6 seems to be the best that a ILI9341 display can do. Try a larger value if the display shows corrupt output, or a smaller value to get higher bandwidth. See ili9341.h and waveshare35b.h for data points on tuning the maximum SPI performance. Safe initial value could be something like -DSPI_BUS_CLOCK_DIVISOR=30.
-DBACKLIGHT_CONTROL=ON: If set, enables fbcp-ili9341 to control the display backlight in the given backlight pin. The display will go to sleep after a period of inactivity on the screen. If not, backlight is not touched.
-DDISPLAY_CROPPED_INSTEAD_OF_SCALING=ON: If set, and source video frame is larger than the SPI display video resolution, the source video is presented on the SPI display by cropping out parts of it in all directions, instead of scaling to fit.
-DDISPLAY_BREAK_ASPECT_RATIO_WHEN_SCALING=ON: When scaling source video to SPI display, scaling is performed by default following aspect ratio, adding letterboxes/pillarboxes as needed. If this is set, the stretching is performed breaking aspect ratio.
-DDISPLAY_SWAP_BGR=ON: If this option is passed, red and blue color channels are reversed (RGB<->BGR) swap. Some displays have an opposite color panel subpixel layout that the display controller does not automatically account for, so define this if blue and red are mixed up.
-DDISPLAY_INVERT_COLORS=ON: If this option is passed, pixel color value interpretation is reversed (white=0, black=31/63). Default: black=0, white=31/63. Pass this option if the display image looks like a color negative of the actual colors.
-DLOW_BATTERY_PIN=
If the above does not work, try specifying -DSPI_BUS_CLOCK_DIVISOR=8 or =10 to make the display run a little slower, or try with -DUSE_DMA_TRANSFERS=OFF to troubleshoot if DMA might be the issue. If you are using another display controller than ILI9341, using a much higher value, like 30 or 40 may be needed. When changing CMake options, you can reissue the CMake directive line without having to reclone or recreate the build directory. However you may need to manually delete file CMakeCache.txt between changing options to avoid CMake remembering old settings.
If the size of the default HDMI output /dev/fb0 framebuffer differs from the resolution of the display, the source video size will by default be rescaled to fit to the size of the SPI display. fbcp-ili9341 will manage setting up this rescaling if needed, and it will be done by the GPU, so performance should not be impacted too much. However if the resolutions do not match, small text will probably appear illegible. The resizing will be done in aspect ratio preserving manner, so if the aspect ratios do not match, either horizontal or vertical black borders will appear on the display. If you do not use the HDMI output at all, it is probably best to configure the HDMI output to match the SPI display size so that rescaling will not be needed. This can be done by setting the following lines in /boot/config.txt:
These lines hint native applications about the default display mode, and let them render to the native resolution of the TFT display. This can however prevent the use of the HDMI connector, if the HDMI connected display does not support such a small resolution. As a compromise, if both HDMI and SPI displays want to be used at the same time, some other compatible resolution such as 640x480 can be used. See Raspberry Pi HDMI documentation for the available options to do this.
The refresh speed of the display is dictated by the clock speed of the SPI bus that the display is connected to. Due to the way the BCM2835 chip on Raspberry Pi works, there does not exist a simple speed=xxx Mhz option that could be set to define the bus speed. Instead, the SPI bus speed is derived from two separate parameters: the core frequency of the BCM2835 SoC in general (core_freq in /boot/config.txt), and the SPI peripheral CDIV (Clock DIVider) setting. Together, the resulting SPI bus speed is then calculated with the formula SPI_speed=core_freq/CDIV.
Adjust the CDIV value by passing the directive -DSPI_BUS_CLOCK_DIVISOR=number in CMake command line. Possible values are even numbers 2, 4, 6, 8, .... Note that since CDIV appears in the denominator in the formula for SPI_speed, smaller values result in higher bus speeds, whereas higher values make the display go slower. Initially when you don"t know how fast your display can run, try starting with a safe high setting, such as -DSPI_BUS_CLOCK_DIVISOR=30, and work your way to smaller numbers to find the maximum speed the display can cope with. See the table at the end of the README for specific observed maximum bus speeds for different displays.
Perhaps a bit counterintuitively, underclock the core. Setting a smaller core frequency than the default turbo 400MHz can enable using a smaller clock divider to get a higher resulting SPI bus speed. For example, if with default core_freq=400 SPI CDIV=8 works (resulting in SPI bus speed 400MHz/8=50MHz), but CDIV=6 does not (400MHz/6=66.67MHz was too much), you can try lowering core_freq=360 and set CDIV=6 to get an effective SPI bus speed of 360MHz/6=60MHz, a middle ground between the two that might perhaps work. Balancing core_freq= and CDIV options allows one to find the maximum SPI bus speed up to the last few kHz that the display controller can tolerate. One can also try the opposite direction and overclock, but that does then of course have all the issues that come along when overclocking. Underclocking does have the drawback that it makes the Pi run slower overall, so this is certainly a tradeoff.
On the other hand, it is desirable to control how much CPU time fbcp-ili9341 is allowed to use. The default build settings are tuned to maximize the display refresh rate at the expense of power consumption on Pi 3B. On Pi Zero, the opposite is done, i.e. by default the driver optimizes for battery saving instead of maximal display update speed. The following options can be controlled to balance between these two:
If your SPI display bus is able to run really fast in comparison to the size of the display and the amount of content changing on the screen, you can try enabling #define UPDATE_FRAMES_IN_SINGLE_RECTANGULAR_DIFF option in config.h to reduce CPU usage at the expense of increasing the number of bytes sent over the bus. This has been observed to have a big effect on Pi Zero, so is worth checking out especially there.
If the SPI display bus is able to run really really really fast (or you don"t care about frame rate, but just about low CPU usage), you can try enabling #define UPDATE_FRAMES_WITHOUT_DIFFING option in config.h to forgo the adaptive delta diffing option altogether. This will revert to naive full frame updates for absolutely minimum overall CPU usage.
In display.h there is an option #define TARGET_FRAME_RATE
A pleasing aspect of fbcp-ili9341 is that it introduces very little latency overhead: on a 119Hz refreshing ILI9341 display, fbcp-ili9341 gets pixels as response from GPIO input to screen in well less than 16.66 msecs time. I only have a 120fps recording camera, so can"t easily measure delays shorter than that, but rough statistical estimate of slow motion video footage suggests this delay could be as low as 2-3 msecs, dominated by the ~8.4msecs panel refresh rate of the ILI9341.
This does not mean that overall input to display latency in games would be so immediate. Briefly testing a NES emulated game in Retropie suggests a total latency of about 60-80 msecs. This latency is caused by the NES game emulator overhead and extra latency added by Linux, DispmanX and GPU rendering, and GPU framebuffer snapshotting. (If you ran fbcp-ili9341 as a static library bypassing DispmanX and the GPU stack, directly linking your GPIO input and application logic into fbcp-ili9341, you would be able to get down to this few msecs of overall latency, like shown in the above GPIO input video)
Interestingly, fbcp-ili9341 is about ~33msecs faster than a cheap 3.5" KeDei HDMI display. I do not know if this is a result of the KeDei HDMI display specifically introducing extra latency, or if all HDMI displays connected to the Pi would have similar latency overhead. An interesting question is also how SPI would compare with DPI connected displays on the Pi.
Unfortunately a limitation of SPI connected displays is that the VSYNC line signal is not available on the display controllers when they are running in SPI mode, so it is not possible to do vsync locked updates even if the SPI bus bandwidth on the display was fast enough. For example, the 4 ILI9341 displays I have can all be run faster than 75MHz so SPI bus bandwidth-wise all of them would be able to update a full frame in less than a vsync interval, but it is not possible to synchronize the updates to vsync since the display controllers do not report it. (If you do know of a display that does actually expose a vsync clock signal even in SPI mode, you can try implementing support to locking on to it)
You can however choose between two distinct types of tearing artifacts: straight line tearing and diagonal tearing. Whichever looks better is a bit subjective, which is why both options exist. I prefer the straight line tearing artifact, it seems to be less intrusive than the diagonal tearing one. To toggle this, edit the option #define DISPLAY_FLIP_ORIENTATION_IN_SOFTWARE in config.h. When this option is enabled, fbcp-ili9341 produces straight line tearing, and consumes a tiny few % more CPU power. By default Pi 3B builds with straight line tearing, and Pi Zero with the faster diagonal tearing. Check out the video Latency and tearing test #2: GPIO input to display latency in fbcp-ili9341 and tearing modes to see in slow motion videos how these two tearing modes look like.
Another option that is known to affect how the tearing artifact looks like is the internal panel refresh rate. For ILI9341 displays this refresh rate can be adjusted in ili9341.h, and this can be set to range between ILI9341_FRAMERATE_61_HZ and ILI9341_FRAMERATE_119_HZ (default). Slower refresh rates produce less tearing, but have higher input-to-display latency, whereas higher refresh rates will result in the opposite. Again visually the resulting effect is a bit subjective.
To get tearing free updates, you should use a DPI display, or a good quality HDMI display. Beware that cheap small 3.5" HDMI displays such as KeDei do also tear - that is, even if they are controlled via HDMI, they don"t actually seem to implement VSYNC timed internal operation.
Having no vsync is not all bad though, since with the lack of vsync, SPI displays have the opportunity to obtain smoother animation on content that is not updating at 60Hz. It is possible that content on the SPI display will stutter even less than what DPI or HDMI displays on the Pi can currently provide (although I have not been able to test this in detail, except for the KeDei case above).
The main option that affects smoothness of display updates is the #define USE_GPU_VSYNC line in config.h. If this is enabled, then the internal Pi GPU HDMI vsync clock is used to drive frames onto the display. The Pi GPU clock runs at a fixed rate that is independent of the content. This rate can be discovered by running tvservice -s on the Pi console, and is usually 59Hz or 60Hz. If your application renders at this rate, animation will look smooth, but if not, there will be stuttering. For example playing a PAL NES game that updates at 50Hz with HDMI clock set at 60Hz will cause bad microstuttering in video output if #define USE_GPU_VSYNC is enabled.
If USE_GPU_VSYNC is disabled, then a busy spinning GPU frame snapshotting thread is used to drive the updates. This will produce smoother animation in content that does not maintain a fixed 60Hz rate. Especially in OpenTyrian, a game that renders at a fixed 36fps and has slowly scrolling scenery, the stuttering caused by USE_GPU_VSYNC is particularly visible. Running on Pi 3B without USE_GPU_VSYNC enabled produces visually smoother looking scrolling on an Adafruit 2.8" ILI9341 PiTFT set to update at 119Hz, compared to enabling USE_GPU_VSYNC on the same setup. Without USE_GPU_VSYNC, the dedicated frame polling loop thread "finds" the 36Hz update rate of the game, and then pushes pixels to the display at this exact rate. This works nicely since SPI displays disregard vsync - the result is that frames are pushed out to the SPI display immediately as they become available, instead of pulling them at a fixed 60Hz rate like HDMI does.
The codebase captures screen framebuffers by snapshotting via the VideoCore vc_dispmanx_snapshot() API, and the obtained pixels are then routed on to the SPI-based display. This kind of polling is performed, since there does not exist an event-based mechanism to get new frames from the GPU as they are produced. The result is inefficient and can easily cause stuttering, since different applications produce frames at different paces. Ideally the code would ask the VideoCore API to receive finished frames in callback notifications immediately after they are rendered, but this kind of functionality does not exist in the current GPU driver stack. In the absence of such event delivery mechanism, the code has to resort to polling snapshots of the display framebuffer using carefully timed heuristics to balance between keeping latency and stuttering low, while not causing excessive power consumption. These heuristics keep continuously guessing the update rate of the animation on screen, and they have been tuned to ensure that CPU usage goes down to 0% when there is no detected activity on screen, but it is certainly not perfect. This GPU limitation is discussed at raspberrypi/userland#440. If you"d like to see fbcp-ili9341 operation reduce latency, stuttering and power consumption, please throw a (kind!) comment or a thumbs up emoji in that bug thread to share that you care about this, and perhaps Raspberry Pi engineers might pick the improvement up on the development roadmap. If this issue is resolved, all of the #define USE_GPU_VSYNC, #define SAVE_BATTERY_BY_PREDICTING_FRAME_ARRIVAL_TIMES and #define SELF_SYNCHRONIZE_TO_GPU_VSYNC_PRODUCED_NEW_FRAMES hacks from the previous section could be deleted from the driver, hopefully leading to a best of all worlds scenario without drawbacks.
The speed of the SPI bus is linked to the BCM2835 core frequency. This frequency is at 250MHz by default (on e.g. Pi Zero, 3B and 3B+), and under CPU load, the core turbos up to 400MHz. This turboing directly scales up the SPI bus speed by 400/250=+60% as well. Therefore when choosing the SPI CDIV value to use, one has to pick one that works for both idle and turbo clock speeds. Conversely, the BCM core reverts to non-turbo speed when there is only light CPU load active, and this slows down the display, so if an application is graphically intensive but light on CPU, the SPI display bus does not get a chance to run at maximum speeds. A way to work around this is to force the BCM core to always stay in its turbo state with force_turbo=1 option in /boot/config.txt, but this has an unfortunate effect of causing the ARM CPU to always run in turbo speed as well, consuming excessive amounts of power. At the time of writing, there does not yet exist a good solution to have both power saving and good performance. This limitation is being discussed in more detail at raspberrypi/firmware#992.
By default fbcp-ili9341 builds with a statistics overlay enabled. See the video fbcp-ili9341 ported to ILI9486 WaveShare 3.5" (B) SpotPear 320x480 SPI display to find details on what each field means. Build with CMake option -DSTATISTICS=0 to disable displaying the statistics. You can also try building with CMake option -DSTATISTICS=2 to show a more detailed frame delivery timings histogram view, see screenshot and video above.
The fbcp part in the name means framebuffer copy; specifically for the ILI9341 controller. fbcp-ili9341 is not actually a framebuffer copying driver, it does not create a secondary framebuffer that it would copy bytes across to from the primary framebuffer. It is also no longer a driver only for the ILI9341 controller. A more appropriate name might be userland-raspi-spi-display-driver or something like that, but the original name stuck.
Edit the file config.h and comment out the line #define DISPLAY_OUTPUT_LANDSCAPE. This will make the display output in portrait mode, effectively rotating it by 90 degrees. Note that this only affects the pixel memory reading mode of the display. It is not possible to change the panel scan order to run between landscape and portrait, the SPI displays typically always scan in portrait mode. The result is that it will change the panel vsync tearing mode from "straight line tearing" over to "diagonal tearing" (see the section About Tearing above).
If you do not want to have diagonal tearing, but would prefer straight line tearing, then additionally enable the option #define DISPLAY_FLIP_ORIENTATION_IN_SOFTWARE in config.h. That will restore straight line tearing, but it will also increase overall CPU consumption.
Enable the option #define DISPLAY_ROTATE_180_DEGREES in config.h. This should rotate the SPI display to show up the other way around, while keeping the HDMI connected display orientation unchanged. Another option is to utilize a /boot/config.txt option display_rotate=2, which rotates both the SPI output and the HDMI output.
Note that the setting DISPLAY_ROTATE_180_DEGREES only affects the pixel memory reading mode of the display. It is not possible to flip the panel scan to run inverted by 180 degrees. This means that adjusting these settings will also have effects of changing the visual appearance of the vsync tearing artifact. If you have the ability to mount the display 180 degrees around in your project, it is recommended to do that instead of using the DISPLAY_ROTATE_180_DEGREES option.
If the display controller is one of the currently tested ones (see the list above), and it is wired up to run using 4-line SPI, then it should work. Pay attention to configure the Data/Control GPIO pin number correctly, and also specify the Reset GPIO pin number if the device has one.
If the display controller is not one of the tested ones, it may still work if it is similar to one of the existing ones. For example, ILI9340 and ILI9341 are practically the same controller. You can just try with a specific one to see how it goes.
If fbcp-ili9341 does not support your display controller, you will have to write support for it. fbcp-ili9341 does not have a "generic SPI TFT driver routine" that might work across multiple devices, but needs specific code for each. If you have the spec sheet available, you can ask for advice, but please do not request to add support to a display controller "blind", that is not possible.
Perhaps. This is a more recent experimental feature that may not be as stable, and there are some limitations, but 3-wire ("9-bit") SPI display support is now available. If you have a 3-wire SPI display, i.e. one that does not have a Data/Control (DC) GPIO pin to connect, configure it via CMake with directive -DGPIO_TFT_DATA_CONTROL=-1 to tell fbcp-ili9341 that it should be driving the display with 3-wire protocol.
The performance option ALL_TASKS_SHOULD_DMA is currently not supported, there is an issue with DMA chaining that prevents this from being enabled. As result, CPU usage on 3-wire displays will be slightly higher than on 4-wire displays.
The performance option OFFLOAD_PIXEL_COPY_TO_DMA_CPP is currently not supported. As a result, 3-wire displays may not work that well on single core Pis like Pi Zero.
This has only been tested on my Adafruit SSD1351 128x96 RGB OLED display, which can be soldered to operate in 3-wire SPI mode, so testing has not been particularly extensive.
Displays that have a 16-bit wide command word, such as ILI9486, do not currently work in 3-wire ("17-bit") mode. (But ILI9486L has 8-bit command word, so that does work)
I have done close to everything possible to my displays - cut power in middle of operation, sent random data and command bytes, set their operating voltage commands and clock timings to arbitrary high and low values, tested unspecified and reserved command fields, and driven the displays dozens of MHz faster than they managed to keep up with, and I have not yet done permanent damage to any of my displays or Pis.
Easiest way to do permanent damage is to fail at wiring, e.g. drive 5 volts if your display requires 3.3v, or short a connection, or something similar.
The one thing that fbcp-ili9341 stays clear off is that it does not program the non-volatile memory areas of any of the displays. Therefore a hard power off on a display should clear all performed initialization and reset the display to its initial state at next power on.
Yes, fbcp-ili9341 shows the output of the HDMI display on the SPI screen, and both can be attached at the same time. A HDMI display does not have to be connected however, although fbcp-ili9341 operation will still be affected by whatever HDMI display mode is configured. Check out tvservice -s on the command line to check what the current DispmanX HDMI output mode is.
At the moment fbcp-ili9341 has been developed to only display the contents of the main DispmanX GPU framebuffer over to the SPI display. That is, the SPI display will show the same picture as the HDMI output does. There is no technical restriction that requires this though, so if you know C/C++ well, it should be a manageable project to turn fbcp-ili9341 to operate as an offscreen display library to show a completely separate (non-GPU-accelerated) image than what the main HDMI display outputs. For example you could have two different outputs, e.g. a HUD overlay, a dashboard for network statistics, weather, temps, etc. showing on the SPI while having the main Raspberry Pi desktop on the HDMI.
double check that the display controller is really what you expected. Trying to drive with the display with wrong initialization code usually results in the display not reacting, and the screen stays white,
shut down and physically power off the Pi and the display in between multiple tests. Driving a display with a wrong initialization routine may put it in a bad state that needs a physical power off for it to reset,
if there is a reset pin on the display, make sure to pass it in CMake line. Or alternatively, try driving fbcp-ili9341 without specifying the reset pin,
make sure the display is configured to run 4-wire SPI mode, and not in parallel mode or 3-wire SPI mode. You may need to solder or desolder some connections or set a jumper to configure the specific driving mode. Support for 3-wire SPI displays does exist, but it is more limited and a bit experimental.
This suggests that the power line or the backlight line might not be properly connected. Or if the backlight connects to a GPIO pin on the Pi (and not a voltage pin), then it may be that the pin is not in correct state for the backlight to turn on. Most of the LCD TFT displays I have immediately light up their backlight when they receive power. The Tontec one has a backlight GPIO pin that boots up high but must be pulled low to activate the backlight. OLED displays on the other hand seem to stay all black even after they do get power, while waiting for their initialization to be performed, so for OLEDs it may be normal for nothing to show up on the screen immediately after boot.
If the backlight connects to a GPIO pin, you may need to define -DGPIO_TFT_BACKLIGHT=
fbcp-ili9341 runs a clear screen command at low speed as first thing after init, so if that goes through, it is a good sign. Try increasing -DSPI_BUS_CLOCK_DIVISOR= CMake option to a higher number to see if the display driving rate was too fast. Or try disabling DMA with -DUSE_DMA_TRANSFERS=OFF to see if this might be a DMA conflict.
This suggests same as above, increase SPI bus divisor or troubleshoot disabling DMA. If DMA is detected to be the culprit, try changing up the DMA channels. Double check that /boot/config.txt does not have any dtoverlays regarding other SPI display drivers or touch screen controllers, and that it does NOT have a dtparam=spi=on line in it - fbcp-ili9341 does not use the Linux kernel SPI driver.
Check that the Pi is powered off of a power supply that can keep up with the voltage, and the low voltage icon is not showing up. (remove any avoid_warnings=1/2 directive from /boot/config.txt if that was used to get rid of warnings overlay, to check that voltage is good) It has been observed that if there is not enough power supplied, the display can be the first to starve, while the Pi might keep on running fine. Try removing turbo settings or lowering the clock speed if you have overclocked to verify that the display crash is not power usage related.
Double check the Data/Command (D/C) GPIO pin physically, and in CMake command line. Whenever fbcp-ili9341 refers to pin numbers, they are always specified in BCM pin numbers. Try setting a higher -DSPI_BUS_CLOCK_DIVISOR= value to CMake. Make sure no other fbcp programs or SPI drivers or dtoverlays are enabled.
If the color channels are mixed (red is blue, blue is red, green is green) like shown on the left image, pass the CMake option -DDISPLAY_SWAP_BGR=ON to the build.
If the color intensities look wrong (white is black, black is white, color looks like a negative image) like seen in the middle image, pass the CMake option -DDISPLAY_INVERT_COLORS=ON to the build.
If the colors looks off in some other fashion, it is possible that the display is just being driven at a too high SPI bus speed, in which case try making the display run slower by choosing a higher -DSPI_BUS_CLOCK_DIVISOR= option to CMake. Especially on ILI9486 displays it has been observed that the colors on the display can become distorted if the display is run too fast beyond its maximum capability.
As the number of supported displays, Raspberry Pi device models, Raspbian/Retropie/Lakka OS versions, accompanied C++ compiler versions and fbcp-ili9341 build options have grown in number, there is a combinatorial explosion of all possible build modes that one can put the codebase through, so it is not easy to keep every possible combo tested all the time. Something may have regressed or gotten outdated. Stay calm, and report a bug.
First, make sure the display is a 4-wire SPI and not a 3-wire one. A display is 4-wire SPI if it has a Data/Control (DC) GPIO line that needs connecting. Sometimes the D/C pin is labeled RS (Register Select). Support for 3-wire SPI displays does exist, but it is experimental and not nearly as well tested as 4-wire displays.
Second is the consideration about display speed. Below is a performance chart of the different displays I have tested. Note that these are sample sizes of one, I don"t know how much sample variance there exists. Also I don"t know if it is likely that there exists big differences between displays with same controller from different manufacturers. At least the different ILI9341 displays that I have are all quite consistent on performance, whether they are from Adafruit or WaveShare or from BuyDisplay.com.
In this list, Rated SPI Bus Speed is the maximum clock speed that the display controller is rated to run at. The Obtained Bus Speed column lists the fastest SPI bus speed that was achieved in practice, and the core_freq BCM Core speed and SPI Clock Divider CDIV setting that was used to achieve that rate. Note how most display controllers can generally be driven much faster than what they are officially rated at in their spec sheets.
The Frame Rate column shows the worst case frame rate when full screen updates are being performed. This occurs for example when watching fullscreen video (that is not a flat colored cartoon). Because fbcp-ili9341 only sends over the pixels that have changed, displays such as HX8357D and ILI9486 can still be used to play many games at 60fps. Retro games work especially well.
All the ILI9341 displays work nice and super fast at ~70-80MHz. My WaveShare 3.5" 320x480 ILI9486 display runs really slow compared to its pixel resolution, ~32MHz only. See fbcp-ili9341 ported to ILI9486 WaveShare 3.5" (B) SpotPear 320x480 SPI display for a video of this display in action. Adafruit"s 320x480 3.5" HX8357D PiTFTs is ~64% faster in comparison.
The ILI9486L controller based maithoga display runs a bit faster than ILI9486 WaveShare, 50MHz versus 31.88MHz, i.e. +56.8% bandwidth increase. However fps-wise maithoga reaches only 13.56 vs WaveShare 12.97 fps, because the bandwidth advantage is fully lost in pixel format differences: ILI9486L
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