Author Topic: LCD issues  (Read 762 times)


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LCD issues
« on: October 04, 2021, 09:24:15 AM »
I'm trying to troubleshoot the LCD screen not working (full disclosure: it's not soldered yet so that could be the reason it's not working). If I try to run the script I get the following error below. I'm also planning to check my soldering. On the troubleshooting page you say to check pins 1, 2, 3, 9, 19, 23, 24, 31. Which pins on the LCD screen do each of these pins map to?

Code: [Select]
File "/home/patch/Pimoroni/gfxhat/examples/", line 49 in <module>
touch.set_led(x, 1)
File "/usr/local/lib/python3.7/dist-packages/gfxhat/", line 49, in set_led
File "/usr/local/lib/python3.7/dist-packages/gfxhat/", line 26, in setup
_cap1166 = cap1xxx.Cap1166(i2c_addr=I2C_ADDR)
File "/usr/lib/python3/dist-packages/", line 283, in __init__
self.product_id = self._get_product_id()
File "/usr/lib/python3/dist-packages/", line 469, in _get_product_id
return self._read_byte(R_PRODUCT_ID)
File "/usr/lib/python3/dist-packages/", line 494, in _read_byte
return self.i2c.read_byte_data(self.i2c_addr, register)
OSError: [Errno 121] Remote I/O error


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Re: LCD issues
« Reply #1 on: October 04, 2021, 02:39:23 PM »
Update: I verified that the screen works that I'm getting 3.3v for the VCC pin and -5.08v for the LED pin, but I can now only get it to show a blank white screen. Part of the issue was a loose fitting connection since the screen hasn't been soldered yet. That will be fixed once I cutout the enclosure.

Running the script shows the printed text in PuTTY but not on the screen. I still get the same error message.

One question I have is when I map out all the pins for the LCD screen, it doesn't match the pins mentioned in the troubleshooting page. I have the following mapping:
VCC - 17
GND - 25
CS - 24
RESET - 29
DC - 31
MOSI - 19
SCK - 23
LED - 2, 4
MISO - none

Randall (Admin)

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Re: LCD issues
« Reply #2 on: October 04, 2021, 04:17:59 PM »
The test is only for Original pi-Stomp with the GFXHat monochrome LCD.  No equivalent test for the pi-Stomp Core color LCD yet.  It has the exact pin mappings you list.

The fact that it lights white is good.

The display is driven only by the mod-ala-pi-stomp service, so if it's not running properly, your display is expected to be white.
As the troubleshooting suggests (just updated it a bit to make it more clear), run: sudo journalctl -f -u mod-ala-pi-stomp
to see what's going on with that service.

If that doesn't lead to anything try this:
% ps-stop
% ps-run -l debug

If that doesn't suggest anything obvious, send what output you do see, so I can have a look.   


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Re: LCD issues
« Reply #3 on: October 05, 2021, 07:46:33 AM »
The issue was the header pins I was using were too loose. I switched the screen connection to jumpers with thicker pins and the screen works perfectly now! Hopefully this helps someone in the future.