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[HELP] I2C LCD with STM32F4-07VG and CooCox

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New Member
Hello all. I have a problem with my lcd. I use it on our robot to see a parameters on robot with STM32F4-07VG board.

I used lcd 4x20 with i2c wiring and pcf8574 module and also coocox to program it with library from www.stm32f4-discovery.net

The problem is, the lcd is often send the random data (not like there isn't same the baudrate), the text is running random from up to bottom. So i have to reset the board so the lcd will display right text and static text (not running text).

I dont know there is problem with my program or my wiring lcd. Because the case is randomly happen. Sometimes it's happen when the robot have a tremble, sometimes it's happen when the robot is motionless.

Maybe someone know about this problem and can explain to me, thanks :)

*video/pic when the lcd error is come afterward
Last edited:


Well-Known Member
Most Helpful Member
My first thought would be too long connecting wires, causing either voltage drop or transmission line type effects and corrupting the data.

How long are the wires and (if more than a few inches) how thick and what physical arrangement?

Or it could just be a faulty display or bad connection...


Well-Known Member
Most Helpful Member
Are you able to reduce the speed of the I²C and see if the problem goes away?

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