mbed lcd display pricelist
The contrast VO pin seems to have different behaviour on different displays, so you may need to experiment for your display to see anything. I think I"ve seen some work tied to 0V, some to 3.3V, or with a different resistor.
Some displays need a negative voltage at VO. One side of the trimpot is connected to the negative voltage instead of GND in that case. F.i. a Maxim MAX1044 can be used to generate the negative voltage.
The underlying HD44780 chip is a driver used in many LCD character displays. It might sometimes be referred to as Hitachi HD44780U. There are also several compatible clones of this chip in use (eg Samsung KS0066).
This Internet of Things example uses mbed"s networking features to display live RSS news feeds on the LCD. It is based on earlier networking examples from the cookbook that read a web page and the Text LCD library to display characters on a text LCD. CNN Technology news is used for the live RSS feed.
If you still get the net error message, make sure that DHCP service is enabled for your mbed. On some networks, you need to add the module"s MAC address to enable the DHCP server to give it an IP address. It times out with an error, if no IP address is returned in about fifteen seconds. If the news does not display on the LCD after seeing "net OK", you may have DNS problems or a very slow network.
Where N/C is not connected and the top left pin of the TextLCD’s header is GND and the right most pin is D7 in the LCD orientation shown in the images above. The resistor sets the contrast and some LCDs may need a different value or a contrast adjust potentiometer. See Text LCD for additional help, if needed.
(*) Note: some older LCDs may use 5V, but 3.3V is more common on current LCDs. If you cannot find a data sheet to confirm this, try 3.3V first and if the display is still blank (after double checking all other connections and code) it might need 5V. To save jumper wires, this setup uses the four bit interface to transfer ASCII characters to the LCD.
A small portion of the RSS news feed web page containing XML is seen below. The data displayed on the LCD is the title. The format is "
In the video above, mbed is powered up and obtains an IP address from the DHCP server. Net OK appears on the LCD. It then opens and reads a portion of the web page, searches for news items displaying them as they are found on the LCD and reads through the rest of the web page. When it reaches the end of the web page, "Read Complete" is displayed.
7. Use a Google RSS news feed. Google also has several RSS news feeds and news can be searched to generate a new RSS feed. Here is an example https://news.google.com/news/feeds?q=mbed&output=rss.
The uLCD-144-G2 from 4D Systems is a low-cost ($25 qty. 100) smart color LCD display board with a serial interface. They are also available from Sparkfun. It looks like a nice alternative to the now hard to find Nokia 6100 LCD breakout boards. It has a TTL level serial interface and a reset pin. An optional uSD card inserted in the display module"s socket can be used to load fonts, images, and play videos in response to serial commands.
In the drawing above, the pins are labeled from the uLCDs perspective with TX and RX pins. Mbed RX goes to uLCD TX and mbed TX goes to uLCD RX. So mbed TX goes to the middle pin on the connector which is the uLCD"s RX pin. The included cable seen below is plugged into the bottom row of pins and plugged into a breadboard using the male header pins for hookup. Note that on the cable silkscreen seen in the image below RX and TX have been swapped to indicate the connections needed to the microprocessor pins.
As an alternative, a two row 10-pin M/F header socket with long PCB leads can be used to make a breadboard adapter by cutting off one row of pins. The header socket plugs into the breadboard and the module plugs into the header socket. The second row of pins could also be cutoff on the LCD module itself, but this would preclude later use of the board’s GPIO pins and 3.3V supply for other projects. For more stable mounting, there are 2mm screw holes at the corners that could be used, but the header socket alone holds it rather well given the small size and weight.
The real problem on a breadboard is shorting the 3.3V pin to the reset pin. The board needs a 5V input, but it outputs 3.3V in case it is needed for external devices when it is used in standalone mode. Shorting the other 4 pins does not impede normal serial slave mode operation. Without a reset, the board typically locks up whenever mbed is reset. If the 3.3V pin is carefully bent down 90 degrees towards the center of the board and away from the reset pin, it will plug directly into a breadboard and work as seen in the photo below. The 3.3V pin could be bent back later if it is ever needed, but don’t count on this working more than once or twice before it breaks off. It would be a good idea to just leave it bent over and use a F/M flexible jumper wire to connect to it, if 3.3V from the display module is ever needed later in other projects. This might be the best solution for most users that want to plug it directly into a breadboard, avoid cutting off pins and avoid hooking it up through another connector.
If you are using an mbed plugged into an application board or other baseboard, use the cable provided with the display and stick short jumper wires in one end of the display"s cable connector and the other end of the jumper wires into the mbed header pin sockets that are found on most of these boards.
Initially, it would seem that the existing mbed cookbook 4DGL library would work with this module. It turns out that it has a different processor, Goldelox, and a different but similar command set than the earlier 4D Systems displays supported by the 4DGL mbed library. So a fork of 4DGL was required with quite a few changes in #defines for command values and baud rate divisors. Some functions are not available and some now have 16-bit arguments instead of 8. The basic features used in the demo code below work correctly and some additional work on the new library code could add other features. Support was also added for the use of printf by using the Stream base class and providing _putc and _getc virtual functions. With some minor changes (#defines for number of x and y pixels) the library should also work with the other small LCD displays from 4D systems that use the Goldelox processor. The large LCD modules and modules with touch use a different processor.
Video of demo code. A micro SD card on the LCD module is required for images and videos. The display is actually a bit more colorful and clearer than it appears in the video. Demos include text using printfs, basic graphics commands, a simple bouncing ball animation, computing the Mandelbrot set pixel by pixel, a Plasma wave BLIT, a JPEG image, and a *.wmv video clip.
The more complex Mandelbrot and Plasma wave demo code is not listed here for brevity but can be found after the code seen above in main.cpp in the uLCD144G2_demo program with the download link below.
Fork of 4DGL lib for uLCD-144-G2. Different command values needed. See https://mbed.org/users/4180_1/notebook/ulcd-144-g2-128-by-128-color-lcd/ for instructions and demo code.
The Goldelox Serial Command Manual explains the command set used in serial slave mode. It works in serial slave mode out of the box. Mbed can send it data too fast at higher baud rates and some small time delays (<=1ms) between characters in the library code are needed to avoid dropping characters when sending out some of the longer commands such as text string (perhaps a display UART buffer overflow?). Each complete command sent gets back an acknowledge character and the library code waits for it for synchronization.
After some experimentation with delays, the driver library now works up to the LCD"s maximum supported baud rate of 600,000. For extreme overclockers, the undocumented baud rates of 750,000, 1,000,000, 1,500,000 and 3,000,000 are running this demo successfully on the mbed LPC1768 with the current delay setup. On other mbed platforms, it will depend on the processor"s baud rate clock and divisor hardware. The quickest way to find out is likely to be through experimentation. The mbed serial API computes the closest possible baud rate match. The demo starts out with 9600 baud which should work on any platform. After the first demo screen, the baud rate is changed on the display and mbed with uLCD.baudrate(value). If it hangs in the demo with the message, "Change baudrate", that baud rate is not working on the platform. For fast transfers and more bandwidth, most applications should use the highest baud rate that works.
The Free 4D Workshop IDE (click "download" icon on that page and again on the next page for download) contains tools to translate fonts, images, and videos on a PC into formats used on the module’s micro SD card in response to serial display commands. This data is then stored on an unformatted uSD card mounted on the PC. Most laptops have an SD reader slot and many uSD cards come with a larger SD adapter, if not there are low cost USB to SD adapters that can be used on a PC. After writing the files, the uSD card is then removed from the PC and inserted in the display module. Serial commands from mbed can then load the fonts, images, and play video clips. For speed, the unformatted uSD card uses disk sector addresses in the serial commands and not filenames in a directory to locate this data, and files are stored in a contiguous RAW format. The procedure to create these files with the IDE tools is described in more detail in two application notes:
The module now comes with the serial mode firmware preinstalled, so it is not necessary to reprogram the module"s firmware to use these features as shown in the manuals with the special programming cable. When starting a new project in the IDE tool, be sure to select the correct LCD module and "Serial". This means that the display"s special IDE tools only need to be used to convert font, image, and video files and write them to the uSD card. The optional programming cable is not needed to write to the uSD card from the PC.
Using the 4D Workshop IDE, a Windows True Type Font was converted to RAW format and written on the unformatted uSD card. The initial steps are not intuitive, so be sure to read the font application note. The new font from the uSD card was selected and a double size "hello world" message was printed out to the display as seen in the image above. The serial commands sent from mbed are shown in the code below . The disk sector address varies depending on what files are already on the uSD card. In this case, nothing else was on the uSD card (i.e., 0,0). In addition to the new IDE tools, there is also an older free True Type Font conversion tool that can be used to generate font files for the uSD card or even C include files with font data.
Paint.net was used to resize the original jpeg image to 128 by 128. The IDEs disk partition tool, RMPet, was used to create two partitions on the uSD card, one FAT and one unformatted (50/50 on a 2G uSD) . The graphics composer tool (tool in IDE) converted the image file and created the new image file on the unformatted partition on the SD card. Windows will not be able to read files on a RAW SD card.This tool can also resize images and *.wmv videos for the display by selecting the file and clicking the "edit" button. It reported which sector address to use for the image (listed in project"s *.GC file).
JPEG, BMP, and other encoded image files could also be stored on a filesystem on mbed such as the SD card, local filesystem, or a USB flash drive. It could be read, decoded, and sent to the display using the BLIT (BLock Image Transfer) command. A fairly complex program is required to decode image files and the RAM buffers needed for decoding use most of the available RAM on mbed, so not much is left for any other purpose such as networking or the RTOS. Information on a student project that ported simple open source JPEG and BMP file decoders to mbed for use on an earlier LCD display is available on the project’s notebook page.
It takes a bit less than 1MB/sec for full screen videos and a couple minutes on a PC to initially render the video into the RAW binary format to write it to the unformatted SD card. The original video clip used in the demo was 900 frames with a play time of 30 seconds. The module"s uSD card video player will be able to support higher video frame rates than sending video data over the serial connection from mbed using the BLIT command.
This is working in the beta version of the driver that I will update in a few days after some more testing - (i.e., flush_media and write_byte needed to read in a two byte return error code from the display).
If the LCD display functions are used in multiple threads, or in a main program and an interrupt routine or callback additional steps are needed to insure mutual exclusion when accessing the LCD"s IO hardware. In general, the use of LCD commands in interrupt routines and callbacks should be avoided and all LCD commands should be placed in main. Global variables can be set in interrupt routines that code in main could check to send out any needed LCD commands.
With the RTOS, a mutex synchronization lock from the RTOS should be used to control access to the display in the case of multiple threads. In such cases, I/O devices typically need mutual exclusion locks to avoid problems. For example, one thread could be in the middle of a long LCD display command just at the point when execution switches to another thread (or interrupt routine) using the display. The display could wind up in the wrong state when a new command is sent before the first one is completed. In general, printf also contains non re-entrant code. An mbed RTOS LCD mutex lock code example (demo4) is available using a different LCD with several threads that display data in different areas of the display. If the RTOS is not being used, it is also possible to implement a mutex lock by disabling and enabling interrupts on a processor with one core.
With the 4D IDE tool it is possible to create high quality images of various instrument gauges. Each frame in the video clip stored on the uSD card shows a different gauge setting, and the display frame command can be used to select the correct frame needed for the desired gauge setting. It is possible to achieve a high update rate (higher than using graphics to redraw the gauge). There is a components page and video demoing this feature with mbed.
The module"s firmware can also be changed to work as a standalone module and a development tool IDE that supports and programs it is also available. The IDE needs a special programming cable available separately to download to the module"s flash. It might be possible to setup a serial bridge program on mbed to use in place of the special programing cable.
Not every single possible serial command is included in the library and more commands could be added. The existing commands are likely the most useful ones, but the remaining ones could be added at the expense of a bit more code memory. To aid debugging of new features, messages can be sent out on the mbed USB serial port at 115200. To enable these debug messages, change DEBUGMODE in the *.h file.
It should be possible to add support for a file system driver on the display"s SD card using the serial commands. The FATFILESYSTEM library needs a couple virtual functions to read and write disk sectors and initialize the disk to provide support for new media. It is about the same as the SD card file system driver, but it is using serial and not SPI for transfers. Might even work for an SD card with two partitions, one formatted for files and another unformatted for fonts, images, and videos.
Student projects using the LCD are shown above. They include a Pac Man game using an accelerometer, an IoT Alarm Clock with networking, an iPod-like music & video player, a Nest-like thermostat using a temperature sensor, and a Missile Command game using pushbuttons.
Rapid and easy prototyping and developmentwith NXP FreeRTOS, MCUXpresso SDK & IDE, Arm mbed, Zephyr OS, and the global ARM ecosystem which provide software libraries and online tools and support
The pixels of the picture must be in the RGB-565 format. The data can be provided as an array in a source or a header file. To convert an image file to the appropriate format, a special utility must be utilized. One such tool is provided by Henning Karlsen, the author of the UTFT display liberary and can be downloaded for free from his web site: http://henningkarlsen.com/electronics/library.php?id=52
The pixels of the picture must be in the RGB-565 format. The data can be provided as an array in a source or a header file. To convert an image file to the appropriate format, a special utility must be utilized. One such tool is provided by Henning Karlsen, the author of the UTFT display liberary and can be downloaded for free from his web site: http://henningkarlsen.com/electronics/library.php?id=52
Wakes up the display from sleep, initializes power parameters. This function must be called first, befor any painting on the display is done, otherwise the positioning of graphical elements will not work properly and any paynt operation will not be visible or produce garbage.
When data is sent to the display after this function completes, the opertion will start from the begining of the assigned address (pixel position) and the pointer will be automatically incremented so that the next data write operation will continue with the next pixel from the memory block. If more data is written than available pixels, at the end of the block the pointer will jump back to its beginning and commence again, until the next address change command is sent to the display.
When the display is in sleep mode, its power consumption is minimized. Before new pixel data can be written to the display memory, the controller needs to be brought out of sleep mode.
Remarks:The result of this operation might not be exactly as expected. Putting the display to sleep will cause the controller to switch to the standard color of the LCD, so depending on whether the display is normally white, or normally dark, the screen might or might not go dark. Additional power saving can be achieved, if the backlight of the used display is not hardwired on the PCB and can be controlled via the BL pin.
The above diagram shows complete pinout diagram of ARM MBED board, which is commonly used forinterface and their locations. Note that all the numbered pins (p5-p30) can also be used as DigitalIn (DigitalInput) and DigitalOut (Digital Output) interfaces.
SPI is a serial communication protocol that uses 4 wires (MOSI-Master Out Slave In, MISO-Master In Slave Out, SCK-Serial Clock, SS-Slave Select) for communication between devices that support this protocol. It has 2 SPI (Serial Peripheral Interface) interfaces, SPI0 and SPI1. Many digital displays, ADC chips, SD cards support SPI protocol.
MCU– STM32F103ZE - high-performance ARM® Cortex™-M3 32-bit RISC core operating at a 72 MHz frequency, high-speed embedded memories (Flash memory - 512 Kbytes and SRAM - 64 Kbytes), and an extensive range of enhanced I/Os and peripherals connected to two APB buses.
Analog pins A4 (SDA) and A5 (SCL) support I2C (TWI) communication using the Wire library. This library can be used to communicate between the Arduino Nano and sensors, displays, other Arduino boards, etc.
If you want to use the Arduino Nano 33 BLE or BLE Sense with the Arduino Desktop IDE, you need to add the Arduino nRF528x mbed Core to it. To do this go to Tools > Board > Boards Manager. Now search for ‘nano 33 ble’ and select Arduino nRF528x Boards (Mbed OS) by Arduino. Select the latest version and click Install.
You can use the same procedure as for the Arduino Nano 33 BLE to install the Arduino nRF528x mbed Core (see above). Because the Arduino Nano 33 BLE Sense is a hardware variation of the Arduino Nano 33 BLE, both boards are recognized as the Arduino nano 33 BLE and this is normal. In the board manager and the board selection, you will only find Arduino Nano 33 BLE.
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