Posts: 3
Joined: Wed Oct 03, 2018 7:33 am

CM3 get more GPIO

Wed Oct 03, 2018 7:45 am

Hello everyone,
I currently working on a project with the new CM3. I would like to get more GPIO for my project, because I have a large number of digital signal inputs to operate. I know that expanders can be used, but I would like to use unused pins. I have free pins from HDMI, CAM or DSI interfaces. Is there a person who uses these pins as a standard GPIO ? Thank you in advance for all the answers. ;)
Best regards,

Posts: 1480
Joined: Tue Jun 30, 2015 1:35 pm

Re: CM3 get more GPIO

Wed Oct 03, 2018 12:51 pm

You can't use HDMI/CSI/DSI as GPIO. You should use I2C port expanders i.e. or some MCU which will be able to deal with them in real time.

Posts: 346
Joined: Fri Jan 01, 2016 10:27 pm

Re: CM3 get more GPIO

Wed Oct 03, 2018 7:52 pm

What are these digital inputs?
Can they be scanned as a matrix?

Posts: 6
Joined: Tue Sep 25, 2018 2:11 pm
Location: Denver, CO, USA

Re: CM3 get more GPIO

Sat Oct 13, 2018 8:09 pm

I can verify that the HDMI, DSI, CSI, and SDX pins cannot be reallocated for any other purpose. You are limited to 46 GPIO pins and 2 1.8V GPIO on the CM3 and CM3L. All the other pins are Broadcom proprietary and locked down in the Kernel and firmware; as such there is no way to configure directionality, pull, or function of the pins or even access the state of those pins from within the OS. Your options as I see would be an IO expander, MCU, or perhaps the input itself could be serialized.

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