raspbian lcd displays random characters manufacturer
Many of these LCD controllers differ slightly from the HD44780 controller in things like the initialization sequence, minimum delay between commands and maybe other ways I don"t know of.
try putting a 1n4148 diode between the 5V supply and the 5V of the LCD, so the LCD will get around 4.5V, that is enough for the LCD, and lowers its logical input levels enough so that it sees 3V3 logic highs as "1" reliably. The garbled letters, and blocks are due to the LCD sometimes seeing a "1" as a zero and that corrupts all communication between the PI and the LCD.
Its a well know problem when trying to drive an LCD with 3V3 levels, it actually needs minimally 3.5V when its powered with 5V (70 % of VCC = 0.7 x 5.0 = 3.5).
In the photos above the Pi is a Model B Rev 2 so should work fine with my tutorial. Random characters is usually a sign it has not been initialized correctly. Again this could be caused by intermittent connections.
I was having the same problem as the OP on my current build with an I2C back-packed LCD getting corrupted. I"d tried all kinds of things to fix the problems - changing the delays, trying different libraries, and pulling out hair with no joy in fixing it.
For anyone else with this problem, you may have what I have if you"re doing event-driven code e.g. from from a switch or rotary encoder. I was getting events triggered while the python code was trying to communicate with the LCD screen - which themselves tried to write to the LCD.
I also had the same problem with scrambled characters on my display. I found that there was a short between the data lines on the expander board where it is soldered to the display board. Once I cleaned up the messy solder, the display worked perfectly.
My code seems to work for outputting to the console, however when I try to output to the LCD, it gives some weird characters and stops. Not sure what to do as i"m not a python wiz (you"d think id be more like php, but nah lol).
I"m using a newly bought 32GB SanDisk Extreme for the Ubuntu. I have another SD card which has Raspbian on it which is working perfectly well with my current display setup--I"m using an old monitor that accepts VGA only. I have a brand-less uHDMI-to-VGA adapter that I"ve been using with my Raspbian.
On each attempt, I format the SD card to FAT32 on Windows using SDCardFormatter, then flash the image from either Raspbian (sudo dd) or Windows (Win32DiskImager), again following Canonical"s instructions. I"ve tried flashing both the 32-bit and 64-bit images. Result is the same for both HDMI ports.
From experience, each of the raspberry PI"s model (and operating system) has their own peculiar issues and fixes, so to keep things fairly regular for this article, I will assume you are using a Raspberry Pi 3 and running the latest version of the Raspbian stretch OS.
This can be solved by formatting the SD card and ensuring the correct noob files are copied to it. If this doesn’t work, try another SD card or the same SD card on another raspberry pi. If the problem persists after doing all this, it might save you more time to install Raspbian stretch or any other distro.
This is more of a security feature built into the Raspberry Pi stretch OS rather than an error. Communication over SSH is disabled for a raspberry pi running a fresh install of the raspbian stretch.
When the key displayed on the screen is different from the one pressed on the keyboard especially the # key. This error, most times occurs as a result of the default UK keyboard configuration of the raspbian and NOOBS software.
From experience, each of the raspberry PI"s model (and operating system) has their own peculiar issues and fixes, so to keep things fairly regular for this article, I will assume you are using a Raspberry Pi 3 and running the latest version of the Raspbian stretch OS.
This can be solved by formatting the SD card and ensuring the correct noob files are copied to it. If this doesn’t work, try another SD card or the same SD card on another raspberry pi. If the problem persists after doing all this, it might save you more time to install Raspbian stretch or any other distro.
This is more of a security feature built into the Raspberry Pi stretch OS rather than an error. Communication over SSH is disabled for a raspberry pi running a fresh install of the raspbian stretch.
When the key displayed on the screen is different from the one pressed on the keyboard especially the # key. This error, most times occurs as a result of the default UK keyboard configuration of the raspbian and NOOBS software.
This article shows how to use the SSD1306 0.96 inch I2C OLED display with the Arduino. We’ll show you some features of the OLED display, how to connect it to the Arduino board, and how to write text, draw shapes and display bitmap images. Lastly, we’ll build a project example that displays temperature and humidity readings.
The OLED display doesn’t require backlight, which results in a very nice contrast in dark environments. Additionally, its pixels consume energy only when they are on, so the OLED display consumes less power when compared with other displays.
The model we’re using here has only four pins and communicates with the Arduino using I2C communication protocol. There are models that come with an extra RESET pin. There are also other OLED displays that communicate using SPI communication.
The sizes are set by the actual font. So, the setTextSize() method doesn’t work with these fonts. The fonts are available in 9, 12, 18 and 24 point sizes and also contain 7-bit characters (ASCII codes) (described as 7b in the font name).
The library also provides methods to displays rectangles with round corners: drawRoundRect() and fillRoundRect(). These methods accepts the same arguments as previous methods plus the radius of the corner. For example:
In this section we’ll build a project that displays temperature and humidity readings on the OLED display. We’ll get temperature and humidity using the DHT11 temperature and humidity sensor. If you’re not familiar with the DHT11 sensor, read the following article:
The following methods draw shapes (such as those above) onto the FrameBuffer. They only become visible to the user once the lcd.show() instruction is executed.
Write text to the FrameBuffer using the coordinates as the upper-left corner of the text. The colour of the text can be defined by the optional argument but is otherwise a default value of 1. All characters have dimensions of 8x8 pixels and there is currently no way to change the font.
Each program contains the screen driver code, sets up the buttons/joystick (if applicable), sets the width and height variables, loads the essential libraries, defines the colour (R, G, B) and clear (c) procedures, then displays some colour checking text like this:
Using lcd.fill_rect, fill the whole screen green and then fill the middle of the screen black, leaving a 10 pixel border. Put red 10-pixel squares in each corner.
Draw a dark grey rectangle in the centre of the screen. Draw 500 white pixels inside the square, none touching the edge. (Random was explained in the previous display tutorial.)
We"ve provided some optimised extended graphics example programs to drive some of the popular boards here. Download the file for your board then read on (rename the files if your download adds weird characters at the end):
This is routine is very complicated. It splits the original triangle into two with a horizontal line and then fills them in. If you uncomment all the # lcd.show() lines and sleep instructions it will slow right down and you can see it working (unfortunately, the 2” display needs such a large buffer that there is not enough memory for the filled triangles code):
For the imports we added the math library as this is needed for Sin and Cos in graph plotting. The random library has also been imported, for the randomly generated triangles. These are followed by the basic LCD board setup we covered earlier.
You may have noticed that on some screens the text is very small and difficult to read. In a following tutorial will add an extra font, with more characters, which we can display in different sizes.
Previous examples connect the white LED backlight to power. The following example is specifically for those using an LCD with a RGB LED backlight. The only difference between the connection is the LED"s backlight on pins 15-18.
When I start my code, it displays as expected the initial screen on the LCD (as defined in setup() function) and then the temperature. But suddenly the LCD displays random characters, see attached, and somehow never stop displaying random characters until i restart the board.
Displaying ASCII characters on MXN lcd is very easy. Where M represents number of coulombs and N number of rows. You just need to know about the internal structure of character lcds, registers of character lcds and the characters supported by lcd controller. Below tutorial will help you in knowing about the internal structure of lcd.
Normally lcd contains HD44780 controller in them. Hd44780 is responsible for all the communications with external controller and displaying text on lcd screen. HD44780 is designed by Hitachi and it supports 255 characters. Which means you can display 255 different characters on lcd directly through its controller. The supported characters are ASCII, Digits(0,9) and Japanese characters. Refer to data sheet of controller if you want to know about all characters and their address in ROM of hd44780 lcd controller.
Now to display ASCII character on 16×2 lcd simply pass the address of the ASCII characters present in 16×2 lcd controller ROM(read only memory). I did same in my code. Started from the first character and prints all of them one by one on lcd. Some characters are missing in ROM of hd44780 and special Japanese language characters are present on their locations. So some Japanese language characters will also be displaced on lcd. Few characters in ROM are greater than 5×10 font. These characters will not appear on lcd. Their decimal value will be displayed on lcd but they will not appear on the lcd.
NOTE: You will see some spaces and weird shape characters displayed on lcd. Those characters are present in controller of 16×2 lcd that’s why they are displayed on lcd. Some Japanese characters will also be displayed on lcd. All the characters present in lcd controller will be displayed on lcd. Characters present in HD44780 lcd controller are given below. Pic is taken from data sheet of hd44780 lcd controller.
Coming to the project code. On first row of 16×2 lcd decimal values of ASCII characters will be displayed and on second row ASCII characters will be displayed. ASCII characters start from 34 location of the hd44780 ROM location. So in code i started the ASCII characters from 34th location.
Each character will appear on 16×2 lcd for 1 second after 1 second it disappears and the next ASCII character will appear on 16×2 lcd with its corresponding decimal value.
Some more projects on displaying ASCII characters on 16×2 lcd using various microcontrollers. Each project code is open source. You an use and modify it according to your needs.
Pin 5Is the Read/Write pin. In read mode, this pin is used to get feedback from the LCD to work out if the LCD can accept commands or to indicate it is too busy.
If read is enabled and Pin4 on the LCD is connected to a pin on your Raspberry Pi, there is a chance that you can destroy your Pi. We only ever want to write to the LCD, we never want to read from it. So this should always be connected to ground.
Pin 6The enable pin (E)functions as the command/data latching signal for the LCD. The LCD will latch in whatever is on the Data Bits and process it on the falling edge of the E signal
Below shows how to wire up the LCD to the Raspberry Pi. We will be using 4 pin mode, so there is no need to connect pins 7 to 10. This LCD doesn"t use the backlight pins, pins 15 and 16. It also doesn"t use the contrast pin, pin 3.
The code below is a very simple example of displaying some text on the top line of the LCD. There is a complete list of all the functions in the LCD library on the WiringPiwebsite.#include