raspbian lcd displays random characters made in china

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.

Connecting an LCD to your Raspberry Pi will spice up almost any project, but what if your pins are tied up with connections to other modules? No problem, just connect your LCD with I2C, it only uses two pins (well, four if you count the ground and power).

In this tutorial, I’ll show you everything you need to set up an LCD using I2C, but if you want to learn more about I2C and the details of how it works, check out our article Basics of the I2C Communication Protocol.

There are a couple ways to use I2C to connect an LCD to the Raspberry Pi. The simplest is to get an LCD with an I2C backpack. But the hardcore DIY way is to use a standard HD44780 LCD and connect it to the Pi via a chip called the PCF8574.

The PCF8574 converts the I2C signal sent from the Pi into a parallel signal that can be used by the LCD. Most I2C LCDs use the PCF8574 anyway. I’ll explain how to connect it both ways in a minute.

I’ll also show you how to program the LCD using Python, and provide examples for how to print and position the text, clear the screen, scroll text, print data from a sensor, print the date and time, and print the IP address of your Pi.

Connecting an LCD with an I2C backpack is pretty self-explanatory. Connect the SDA pin on the Pi to the SDA pin on the LCD, and the SCL pin on the Pi to the SCL pin on the LCD. The ground and Vcc pins will also need to be connected. Most LCDs can operate with 3.3V, but they’re meant to be run on 5V, so connect it to the 5V pin of the Pi if possible.

If you have an LCD without I2C and have a PCF8574 chip lying around, you can use it to connect your LCD with a little extra wiring. The PCF8574 is an 8 bit I/O expander which converts a parallel signal into I2C and vice-versa. The Raspberry Pi sends data to the PCF8574 via I2C. The PCF8574 then converts the I2C signal into a 4 bit parallel signal, which is relayed to the LCD.

Now we need to install a program called I2C-tools, which will tell us the I2C address of the LCD when it’s connected to the Pi. So at the command prompt, enter sudo apt-get install i2c-tools.

Now reboot the Pi and log in again. With your LCD connected, enter i2cdetect -y 1 at the command prompt. This will show you a table of addresses for each I2C device connected to your Pi:

We’ll be using Python to program the LCD, so if this is your first time writing/running a Python program, you may want to check out How to Write and Run a Python Program on the Raspberry Pi before proceeding.

The function mylcd.lcd_display_string() prints text to the screen and also lets you chose where to position it. The function is used as mylcd.lcd_display_string("TEXT TO PRINT", ROW, COLUMN). For example, the following code prints “Hello World!” to row 2, column 3:

On a 16×2 LCD, the rows are numbered 1 – 2, while the columns are numbered 0 – 15. So to print “Hello World!” at the first column of the top row, you would use mylcd.lcd_display_string("Hello World!", 1, 0).

You can create any pattern you want and print it to the display as a custom character. Each character is an array of 5 x 8 pixels. Up to 8 custom characters can be defined and stored in the LCD’s memory. This custom character generator will help you create the bit array needed to define the characters in the LCD memory.

By inserting the variable from your sensor into the mylcd.lcd_display_string() function (line 22 in the code above) you can print the sensor data just like any other text string.

These programs are just basic examples of ways you can control text on your LCD. Try changing things around and combining the code to get some interesting effects. For example, you can make some fun animations by scrolling with custom characters. Don’t have enough screen space to output all of your sensor data? Just print and clear each reading for a couple seconds in a loop.

My LCD is showing random characters, see the picture below (the last character blinks, some characters change and over time there are slowly more and more characters). I"m starting to wonder if the LCD I chose has a driver compatible with the LiquidCrystal library, what do you think? If so what can I do to avoid buying another one?

In previous posts I’ve covered using HD44780 16×2 and 20×4 LCD screens with the Raspberry Pi using Python. These are relatively easy to use but require a number of connections to be made to the Pi’s GPIO header. This setup can be simplified with the use of an I2C enabled LCD screen.

The example script will allow you to send text to the screen via I2C. It is very similar to my scripts for the normal 16×2 screen. To download the script directly to your Pi you can use :wget https://bitbucket.org/MattHawkinsUK/rpispy-misc/raw/master/python/lcd_i2c.py

Here is a simple project/tutorial in which i will teach you about how to display ASCII characters on character lcd’s. In this tutorial i am using 16×2 lcd. You can use any other size of lcd if you want but be sure to change the lcd initialization statements in the code. Character lcd’s have a built in controller which controls its operations. Usually character lcd’s has HD44780 controller in them. This controller has pre-defined ASCII characters stored in its ROM(read only memory). When we send any character from external microcontroller on lcd data pins and write it to lcd screen, what happens actually is, the character is received by the lcd controller. 16×2 lcd controller then matches the character with its internal ROM characters if matches is found it then displays the character on 16×2 lcd screen.

16×2 lcd is not limited to displaying ASCII characters. Its internal ROM also contains some special Chinese language characters some special shapes. We can display all of them by calling their addresses in ROM.

We can also display custom character’s on 16×2 lcd. Bycustom characters i mean we can create our own characters and can display them on 16×2 lcd. To display custom characters we utilize the internal CG-RAM(Character generated Random Access Memory) of 16×2 lcd controller. Custom characters generation are not part of this project. I have separate tutorials on them.

Character lcd’s can display character of size 5×8 and 5×10. In 5×8 dimension 5 represents numbers of rows and 8 represents number of coulombs. Sp in a cube of 5×8 and 5×10 we can display our characters. Normally we display characters in 5×7 font. The 8th coulomb we left is for the cursor movement. 5×10 font is not popular and limited characters can be displayed in 5×10 font. Total 32 characters can be displayed in 5×10 matrix and 208 can be displayed in 5×8 matrix cube. An image of characters with their addresses in ROM of hd44780 lcd controller data sheet is below.

Going through the data sheet of HD44780 lcd controller. You will see the character’s that are stored in the ROM(random access memory) of the controller. Character’s with their addresses are listed in the data sheet. You can see the characters and their addresses in the picture given above.

I am going to invoke the addresses of each characters/numbers special characters ASCII characters stored in the ROM and they will display on 16×2 lcd screen automatically. On first line of lcd i am printing the decimal value of the ASCII character and on the second line i will display the original ASCII character. whole of the ASCII characters in lcd controller ROM will be displayed on lccd screen one by one. The code is placed in while(1) loop so the process will remain continuous unless the power is cut off.

Lcd is interfaced in 8-bit mode with 8051 microcontroller. Lcd data pins are connected to port-2 of 89c51 microcontroller. Lcd rs(register select) pin is connected to port-3 pin#5. Lcd rw(read write) pin is connected to port-3 pin#7 and lcd en(enable) pin is connected to port-3 pin#6. Circuit diagram of the project is below.

The code is very simple we hope that you are already familiar with c/c++ programming language. Code is written and compiled in keil uvision ide. First of all the header file re51.h is included. we have to include in our every project which includes 8051 microcontroller in it. Then the lcd rs(register set) rw(read/write) and en(Enable) pins are defined.

Just copy the code and made your circuit burn the code in your microcontroller. Power the circuit and ascii characters will appear on your 16×2 lcd screen. You can also use another size of screen but take care you have to change just only one statement lcdcmd(0x38). If you want to know about the lcd initialization just visit thebelow tutorial.

Warning: Globally setting Chinese locales in /etc/locale.conf will cause tty to display garbled texts due to the tty glyph limitation of Linux kernel. To properly display Chinese characters under tty, install and configure AUR.

To allow MPlayer to display Chinese subtitles correctly, the key is to make sure the encoding of the subtitle file is consistent with the encoding used in mplayer"s configurations. If the subtitle file is encoded as gbk, use subcp=cp936; If the subtitle file is encoded as utf-8, use subcp=utf8. If the subtitle file is encoded as utf-8 and set to subcp=cp936, some garbled characters will appear. Another simpler method is to set to subcp=enca:zh:ucs-2, so that enca is responsible for the encoding and display of subtitles.

AUR: A multi-platform Chinese dictionary. In addition to Chinese characters, words, idioms, etc., it also contains Hakka, Hokkien, simple foreign language translations, stroke order writing, etc. moedict online address

A while ago, thanks to the joys of eBay and manufacturing in China, I ordered some low-cost 16×2 LCD character screens, and they finally arrived.  Yeah, now I can get down to trying to output some text to the LCD screen, just one of the pieces of the puzzle for creating a metro ‘next train’ monitor.

For the first step, I just wanted to see if I could get it to work, so I started with the Hello World tutorial.  I wired it up using a breadboard, and put in a header that I had into the breadboard, and then set the LCD screen on top, unsoldered.

Second, the tutorial also did not have the backlight lit, which was a mistake.  My LCD was extremely difficult to read without the backlight, so I wired up the backlight by connecting the last two pins to +5v and ground respectively.  While the wiring was done correctly (I check multiple times), the LCD would just output square boxes on the top line.

So I went into investigative mode, first pulling out the multimeter to check the voltages (too clumsy as I needed two hands and had to hold wires to the multimeter leads), and instead used the analog in of the Arduino to read the voltage (1023 = 5v, and 0 = ground).  After several checks I found the problem:  the RW pin was not being successfully pulled to ground.  While on the breadboard it was at 0v, and on the header pin sticking up it was at 0v, when I touched to the plated part of the LCD pin ins, I was getting 5v.  No idea how, and why it was at 5v exactly and not a floating voltage is beyond me.  Either way, obviously not good and despite my attempts to move it around and to hold a wire to it to ground, did not get a change.  I was not sure if the LCD screen had been fried (again, forums had indicated this possibility if you used less than a 10k pot).

Solution was to solder it. As soon as I had done that (thanks to learning how to solder earlier), the LCD display made that first output:  Hello World!, along with the number of seconds since it started.

I wanted to experiment, and instead of controlling via a pot, I wanted to control the contrast by a PWM pin.  This is also part of my objective in a future project.  So I build a display contrast tester, that automatically steps through the different PWM outputs from one of the Arduino PWM pins, changing the contrast based on that output and writing it to the LCD screen and to the serial monitor.  Thus the LCD Contrast Tester was created.

And see the LCD Contrast Tester in action.  You can see about 120 is the best contrast for this LCD, which approximately half (128 would be 50% of the way).

However, one thing that happens is that after a random amount of time, the LCD screen screws up:  it starts scrolling random text, or instead of putting the numbers for the PWM in the right spot, starts changing things elsewhere.

And code for the LCD Contrast Tester.  Note that in this code I also added in digital control of the backlight pin, so that it goes through the first cycle with no backlight, then turns it on for the second cycle, off for the third, etc.  To avoid using this, just put the backlight positive from the LCD (second last pin in the LCD) to +5V, as opposed to digital pin 7.

The random characters are appearing because of the use of the PWM to control the contrast on V0. Apparently, this causes some issue because of the nature of the PWM signal.

I put the V0 back to the pot output, reset the board, and it ran for an hour without an error or random character appearing. Then I put it to the PWM output and within 2 seconds the error had appeared. Going back to the pot output does not fix it: once the error is there, it is there!

If you have this screen (or any other serial device) connected to the same UART that is being used to program the board (ie: any Arduino with one UART and using that UART with the screen (Rx and Tx pins)), you run the risk of inadvertently sending commands during the programming process to the LCD that reconfigure it and cause it to not behave as expected!

Think about it. When you program an Arduino, both Rx and Tx LEDs show activity, meaning that the Arduino IDE is sending data to the board, and the board is responding. If the LCD screen is ALSO connected to the Arduino via the Rx and Tx pins, it too will be reading the bytes that is being send back to the IDE. If there is a byte sequence that includes the command to change the LCD baud rate, defined screen size, or whatever, then your screen will most likely not work correctly unless you send the appropriate commands to reconfigure it.

Either unplug the screen during the programming process, or ensure that the screen is using it"s own UART (another hardware UART or a software UART) so that the programming process does not change the configuration. Otherwise, who knows what baud rate or screen size it will be set too and yes, you will get random characters, no characters, and inconsistent cursor locations. Initially, I had the same problems as others have commented on. I have been using these screens for years without any issues once I realized this gotcha.

All Windows 10 editions include fonts that provide broad language support, and the Windows platform includes font fallback mechanisms designed to ensure that text in any language always displays with legible glyphs rather than boxes. But some apps may take direct dependencies on particular fonts for displaying certain Unicode characters and do not utilize the font fallback mechanisms provided by Windows. In some cases, these apps have taken direct dependencies on fonts that are not present by default on all Windows 10 systems. Because the font that the app is trying to use is not present on the system, some other font gets used to display the text instead, and that font may not support all of the characters being displayed. When a character is displayed using a font that doesn’t support that character, a default “not defined” glyph from that font is used. The “not defined” glyph in most fonts has the appearance of a rectangular box, or some variation of that.

If a Windows Phone app directly depends on one of the fonts listed above for displaying certain Unicode characters and does not make use of font fallback mechanisms provided by Windows, the result would be characters displayed as “square box” glyphs.

If an app depends on one of these fonts for displaying certain Unicode characters and does not make use of font fallback mechanisms provided by Windows, and if the optional font package containing that font is not installed on the system (typically because the system and user profiles are not configured to have the associated language enabled), then the result would be characters displayed as “square box” glyphs.

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).

We have used Liquid Crystal Displays in the DroneBot Workshop many times before, but the one we are working with today has a bit of a twist – it’s a circle!  Perfect for creating electronic gauges and special effects.

LCD, or Liquid Crystal Displays, are great choices for many applications. They aren’t that power-hungry, they are available in monochrome or full-color models, and they are available in all shapes and sizes.

Waveshare actually has several round LCD modules, I chose the 1.28-inch model as it was readily available on Amazon. You could probably perform the same experiments using a different module, although you may require a different driver.

Open the Arduino folder. Inside you’ll find quite a few folders, one for each display size that Waveshare supports. As I’m using the 1.28-inch model, I selected theLCD_1inch28folder.

Once you do that, you can open your Arduino IDE and then navigate to that folder. Inside the folder, there is a sketch file namedLCD_1inch28.inowhich you will want to open.

When you open the sketch, you’ll be greeted by an error message in your Arduino IDE. The error is that two of the files included in the sketch contain unrecognized characters. The IDE offers the suggestion of fixing these with the “Fix Encoder & Reload” function (in the Tools menu), but that won’t work.

The error just seems to be with a couple of the Chinese characters used in the comments of the sketch. You can just ignore the error, the sketch will compile correctly in spite of it.

Unfortunately, Waveshare doesn’t offer documentation for this, but you can gather quite a bit of information by reading theLCD_Driver.cppfile, where the functions are somewhat documented.

The TFT_eSPI library is ideal for this, and several other, displays. You can install it through your Arduino IDE Library Manager, just search for “TFT_eSPI”.

A great demo code sample is theAnimated_dialsketch, which is found inside theSpritesmenu item.  This demonstration code will produce a “dial” indicator on the display, along with some simulated “data” (really just a random number generator).

One of my favorite sketches is the Animated Eyes sketch, which displays a pair of very convincing eyeballs that move. Although it will work on a single display, it is more effective if you use two.

The GC9A01 LCD module is a 1.28-inch round display that is useful for instrumentation and other similar projects. Today we will learn how to use this display with an Arduino Uno and an ESP32.