raspbian lcd displays random characters price

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).

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.

Warning: Arduino and other systems with bootloaders may send "garbage" characters to the display while the system is starting up or being reprogrammed. This may cause the display to be bricked. To avoid this, you can use a software serial library to create a separate serial port from the USB port, as in the following examples. For more information about the library, head over to the reference:

For simplicity, we will be using an Arduino microcontroller. In this example, we connected a serial enabled LCD to the RedBoard programmed with Arduino (basically an Arduino Uno with an ATmega328P).

When you power up the board, you"ll briefly see a SparkFun splash screen, and then the display will go blank. To send text to the board, wait 1/2 second (500ms) after power up for the splash screen to clear, then send text to the display through your serial port. The display understands all of the standard ASCII characters (upper and lowercase text, numbers, and punctuation), plus a number of graphic symbols and Japanese characters. See the HD44780 datasheet for the full list of supported characters.

A common LCD technique is to repeatedly display changing numbers such as RPM or temperature in the same place on the display. You can easily do this by moving the cursor before sending your data.

To move the cursor, send the special character (0xFE), followed by the cursor position you"d like to set. Each cursor position is represented by a number, see the table below to determine the number in decimal to send for a serial enabled LCD set to 16x2:

The Arduino board has a wide variety of compatible displays that you can use in your electronic projects. In most projects, it’s very useful to give the user some sort of feedback from the Arduino.

This is a tiny display with just 1 x 0.96 Inch. This display has a black background, and displays characters in white. There are other similar displays that can show the characters in other colors.

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.

The Matrix Orbital Parallel display series offers a low cost display solution utilizing an industry standard communication interface for simple integration into a wide variety of new and existing applications.  The Light Emitting Diode backlight with configurable brightness and voltage controlled contrast allows the MOP Liquid Crystal Display line to offer a professional display solution with low power impact for any project.  The standard alphanumeric font set also allows up to eight custom characters to be saved in display Random Access Memory for a custom design touch.

CategorySub CategoryFile NameRevisionSizeDescriptionNotesFeaturesChange LogCategorySub CategoryFile NameRevisionSizeDescriptionNotesFeaturesChange LogMOP SeriesMOP Character LCD1.0278.43KiBAll of our Matrix Orbital Alphanumeric displays have HD44780U compatible drivers.

This particular post will cover a bit of technology that most people simply know as "the LCD display". I"m not talking about the computer monitor type of LCD display; no, I"m talking about that small screen on many common pieces of electronics, the one that looks like this.

I"m going to talk about the LCM1602C LCD. The purpose of this post is to get away from a lot of the esoteric "how tos" of this particular display. Ya see, this display is based on the Hitachi HD44780 LCD controller. The nice thing about that is the specifications are readily available. The problem is that the specifications are not readily understood. Yes, I believe that this is an example of "lost in translation".

Let"s talk about the display first. This particular display is a 16 character by 2-line display. Its memory can hold up to 80 characters, 40 on each line of the display. The actual part that displays the characters can only show 16 characters across at any one time. Using the SHIFT command, you can move the part of the lines that are displayed.

I used an Arduino to drive my LCD display simply so that I could drive the various logic lines. I didn"t use any of the specialized Arduino libraries for driving a LCD; instead, I simply used the standard digitalWrite command to send the commands and data. The digitalWrite command merely sets the targetted output pin to either 0 V (GND, or LOW) or to +5 V (HIGH). This is equivalent to opening (LOW) or closing (HIGH) a switch. The difference is that using the Arduino means you don"t have the "bounce" problem. The hard part is that you have to code each HIGH and LOW of each line.

To simplify the steps, I"m going to use a table in which each HIGH is replaced by a 1, and a LOW is replaced by a 0. After each step, the EN (enable) line on the system has to be set HIGH, then LOW. This tells the LCD to read in the data or instructions.

If you happen to be using the normal LCD library for an Arduino, or programming the LCD using a C or C++ based system, then when you program it to, say, show the letter "H", or program it to have the cursor blink, then your programming has to be setting the various lines in a manner similar to what we just did above. Think of this as "assembly language for the LCD".

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.

Once you’ve played with LEDs, switches and stepper motors the next natural step is 16×2 alphanumeric LCD modules. These modules are cheap (less than $10) and easy to interface to the Raspberry Pi. They have 16 connections but you only need to use 6 GPIO pins on your Pi.

Most of the 16×2 modules available are compatible with the Hitachi HD44780 LCD controller. This allows you to buy almost any device and be sure it is going to work in much the same way as any other. There are loads to choose from on eBay with different coloured backlights. The one I purchased had a blue backlight.

This script can be downloaded using this link or directly to your Pi using the following command :wget https://bitbucket.org/MattHawkinsUK/rpispy-misc/raw/master/python/lcd_16x2.py

Additional Notes : RS is low when sending a command to the LCD and high when sending a character. RW is always low to ensure we only ever input data into the module. 8 bit bytes are sent 4 bits at a time. Top 4 bits first and the last 4 bits second. Delays are added between certain steps to ensure the module can react to the signal before it changes.

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.

It runs Raspbian and Pidora, versions of Debian and Fedora Linux. As I Linux administrator for more than a decade, I am seriously comfortable with setting up these baby powerhouses.

I learned of one way to solve the problem: set up a startup script where it speaks the IP address aloud. Then I figured out a second way: run a startup script that displays the IP address on a 16x2 LCD screen.

To understand the limitations, take a piece of graph paper and draw out a set of 5x7 rectangles. See if you can define ANY recognizable Japanese or Chinese characters on your graph paper.

You need a display with a lot more resolution, like an OLED graphics display. You are also struggling against a microcontroller that doesn"t have support for Unicode. It"s just not up to the job. You"d be much better off with a Raspberry Pi and a screen like a smart-phone color LCD screen. Install Linux and you can have native support for Unicode.