Ardusan
Posts: 14
Joined: Fri Jun 04, 2021 1:30 am

CM3, HDMI clashing with GPIO

Mon Jun 07, 2021 12:51 am

I have noticed that there is interference with GPIO 9,10,11 & 19,20,21 which I use to upload F/W to two Microchip PICs (parts of our device), when HDMI screen is active. Not an issue really as HDMI display is used only for debugging, but I am curious as to why is that happening.

PhilE
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 3949
Joined: Mon Sep 29, 2014 1:07 pm
Location: Cambridge

Re: CM3, HDMI clashing with GPIO

Mon Jun 07, 2021 7:40 am

Which carrier is this? You really need to say for CMs.

What is the nature of the interference? Occasional glitches, constant analogue ripple, or something else?

How does the interference manifest, and with what severity?

Ardusan
Posts: 14
Joined: Fri Jun 04, 2021 1:30 am

Re: CM3, HDMI clashing with GPIO

Tue Jun 08, 2021 2:53 am

thanks!

you wrote: "Which carrier is this?" I am not sure I understand what does it mean.

I am using both pickle and picberry (https://github.com/WallaceIT/picberry) on CM3+ (16GB), latest Raspberry OS.
to upload FW to two dsPIC33F. When HDMI display is not active (CM3 booted without display being attached) bot pickle and picberry can upload FW without issue, but when HDMI is active:
pickle seems to program and verify the chip correctly but the result is that dspic fails to perform as designed. Seems there is some corruption of data but not catastrophic - some functionality is fine, some is not.)
picberry fails at verifying the uploaded FW every time. programming takes very long sometimes.

same behavior is for both dspics (using gpios 9,10,11 and 19,20,21)

aBUGSworstnightmare
Posts: 3141
Joined: Tue Jun 30, 2015 1:35 pm

Re: CM3, HDMI clashing with GPIO

Tue Jun 08, 2021 6:12 am

Th4 question is which hardware (baseboard) your CM3 is mounted on!
Is it the CMIO https://www.raspberrypi.org/products/co ... -board-v3/ or a custom board?

Ardusan
Posts: 14
Joined: Fri Jun 04, 2021 1:30 am

Re: CM3, HDMI clashing with GPIO

Wed Jun 09, 2021 7:59 am

Oh, I see. It is a custom board. Are you hinting at layout/rooting interference? That would make sense. I will check with the colleague who is doing the PCB design.

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