Faulty dot3k? - Displaying no text

I’m having a similar problem to some others I’ve seen on the forums; no text displayed on the dot3k.

Everything else seems to run just fine. RGB backlight and white LEDs run through scripts and acts as expected, but always without any text on the LCD itself.

I have run almost every example, with no error messages. The joystick returns the expected response in Terminal in those scripts that it plays a part.

If it’s a problem with contrast then I can’t detect even the faintest of text on the display. I’ve reinstalled twice, and used the display on three different machines (with different SD cards and OS) but still no text.

If it’s a contrast problem, is there as way I can update the firmware or anything?


It’s possible it’s a contrast problem, but unlikely. I’m trying to wrack my brains, and others, for any idea what might be wrong.

I’m guessing the script returns no errors? It might be a faulty Display-o-Tron :(

The firmware of the display can’t be updated, but it might be worth playing with set_contrast using values ~30 or 40.


No errors when running any of the example scripts. They all run but the LCD does not display anything.

I do get an error sometime when exiting a script by CTRL+C. This is full text:

pi@Custard:~/Pimoroni/displayotron/examples/dot3k/basic $ ./hue.py
This example shows how to set the backlight to a hue!
It uses colorsys, rather than the built-in hue function, to show you a colour conversion in Python.
Press CTRL+C to exit.
^CTraceback (most recent call last):
  File "./hue.py", line 20, in <module>
backlight.rgb(r, b, g)
  File "/usr/local/lib/python2.7/dist-packages/dot3k/backlight.py", line 221, in rgb
right_rgb( r, g, b)
  File "/usr/local/lib/python2.7/dist-packages/dot3k/backlight.py", line 205, in right_rgb
set(LED_R_R, r)
  File "/usr/local/lib/python2.7/dist-packages/dot3k/backlight.py", line 82, in set
  File "/usr/local/lib/python2.7/dist-packages/dot3k/backlight.py", line 233, in update
  File "/usr/lib/python2.7/dist-packages/sn3218.py", line 104, in output
i2c.write_i2c_block_data(I2C_ADDRESS, CMD_SET_PWM_VALUES, [channel_gamma_table[i][values[i]] for i in range(18)])

I think this is a faulty LCD, can I do anything about returning it?

Sure thing, drop us an email to support@pimoroni.com mentioning this thread, and they should sort you out a replacement.

It’s probably to do with the voltage boost circuit that supports the LCD. Perhaps a dry joint. The driver chip inside the LCD will be working happily, but without the oomph to actually “light” up the digits.