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[Solved] Raspberry Pi garbled image

Posted: Sat Jan 25, 2014 2:07 am
by Laurynas
Hello,

I have bought OLED128 display and connected it to my Raspberry Pi. Followed wiring and software installation steps from http://www.freetronics.com/pages/oled12 ... spberry-pi. As per instructions, I am using fbtft drivers

I can start X and swap system console, BUT the image on the OLED display I get is garbled:
Console Screenshot.jpg
Console Screenshot
X Screenshot.jpg
X Desktop Screenshot
Tried different RasPi devices, fresh OS (wheezy 2014-01-07), rechecked wiring, disconnected other equipment, changed power supplies, still no go.

Help would be greatly appreciated.

***UPDATE***
Solved the issue by lowering SPI speed: modprobe fbtft_device name=freetronicsoled128 speed=19000000

Re: Raspberry Pi garbled image

Posted: Sat Jan 25, 2014 6:06 am
by cef
Off the top of my head:

First thing I would check is how long the cable you have between the Raspberry Pi and the OLED display is?

If the cable is too long, complicated text and graphics might get corrupted.

Second is to check your 5V power supply for the Raspberry Pi is sticking to 5V and not sagging under the extra load.

Re: Raspberry Pi garbled image

Posted: Sat Jan 25, 2014 6:23 am
by Laurynas
Cables are 15cm long, would that be a problem? I will check on power supply voltages. Although, I have tested with two different ones, supplying 2Amps each.

Command line is not heavy on graphics, but I am still observing constant jitter, i.e. some groups of pixels jumping up and down with very visible color discord.

Re: Raspberry Pi garbled image

Posted: Sun Jan 26, 2014 12:58 am
by Laurynas
Power supply voltage is solid on GPIO pins, I even went ahead and soldered 5cm wires to the headers on RPi and OLED PCB. Still no go, same issue.

I have tried using fbtft Raspberry Pi image, to avoid human error, still same issue.

Any other suggestions?

Re: Raspberry Pi garbled image

Posted: Tue Jan 28, 2014 2:19 am
by Laurynas
After playing around with the the fbtft driver settings I finally got it working with SPI speed set to 19 MHz (default is 20MHz). Guess, driving the display at the max spec did not work in my case. Updating fbtft driver to a more conservative speed may save time for others.

Registered display with the following command: modprobe fbtft_device name=freetronicsoled128 speed=19000000

Hope this will be helpful to others.

Re: Raspberry Pi garbled image

Posted: Tue Jan 28, 2014 2:19 am
by Laurynas
After playing around with the the fbtft driver settings I finally got it working with SPI speed set to 19 MHz (default is 20MHz). Guess, driving the display at the max spec did not work in my case. Updating fbtft driver to a more conservative speed may save time for others.

Registered display with the following command: modprobe fbtft_device name=freetronicsoled128 speed=19000000

Hope this will be helpful to others.

Re: [Solved] Raspberry Pi garbled image

Posted: Tue Jan 28, 2014 10:06 pm
by angusgr
Thanks for updating us Laurynas, glad you got it sorted.

I've added a Troubleshooting section on the Getting Started page that explains how to lower the SPI clock speed, in case anyone else has the same problem:
http://www.freetronics.com/pages/oled12 ... leshooting

- Angus