2,5m cable too long for LCD connected to Arduino UNO?

Question

So i got that 2,5m cable wired with the LCD and the arduino, but i keep getting those weird characters showing up on the LCD. Clearly there is a signal loss between the components but there has to be a solution to the problem. Perhaps by connecting capacitors/resistors to the wires will help? Is there any solution other than not using this long cable?

Answer 1

If the interface you're using is I2C(only two cables from arduino to lcd, vice versa)you have a problem,you need to pull up the sda-scl channel with appropriate resistors, you could (maybe) boost the I2C signal using ti-p82b715 bus extender, I just assume you use I2C (2,5m length?), what interface do you use? SPI? I2C?

Answer 2

I'm presuming this is I2C or SPI, because a Serial cable of 2.5 m should still work.

You can slow both I2C and SPI down.

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In the case of SPI you can call something like this:

SPI.setClockDivider(divider);

Where "divider" is one of:

• SPI_CLOCK_DIV2
• SPI_CLOCK_DIV4
• SPI_CLOCK_DIV8
• SPI_CLOCK_DIV16
• SPI_CLOCK_DIV32
• SPI_CLOCK_DIV64
• SPI_CLOCK_DIV128

The default is SPI_CLOCK_DIV4, so try a larger divider.

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In the case of I2C you can change the clock speed and the prescaler. The default frequency is 100 kHz, but you could make it slower.

TWBR   prescaler   Frequency

  12       1       400   kHz  (the maximum supported frequency)
  32       1       200   kHz
  72       1       100   kHz  (the default)
 152       1        50   kHz
  78       4        25   kHz
 158       4        12.5 kHz

For example, to run at half the frequency (50 kHz) use:

  Wire.begin ();
  TWBR = 152;  

To run at 25 kHz you also need to change the prescaler, eg.

  Wire.begin ();
  TWBR = 78;  
  TWSR |= bit (TWPS0);

In the case of I2C make sure you have pull-up resistors on SDA and SCL in order to get a clean signal. 4.7 k is a reasonable value to try (for both of them) with the other ends connected to +5 V.