I just did an rpi-update (after putting the device tree back to default) - everything functions properly, both buses are alive now. Thanks for the update!

Do you think this would potentially introduce a problem?

I guess so! Thanks for the follow-up and answering so quickly. We'll wait for the update.

I was experiencing the exact same problem - i2c0 on CM1 was working great...if a CM3 is inserted into the same carrier board, i2c0 is no longer accessible (with the same software/device tree/config.txt). In the device tree, attempts to set GPIO pins 0/1 to ALT0 (i2c0) functions did not work...'gpio ...

I started over with the recent source at https://raw.githubusercontent.com/raspb%20...%20t-blob.dts , and built the changes on top of that (I was using the minimal compute module example before). I'm happy to report that it was successful, and that there are not any SD card problems now. Thanks for ...

Can you attach a scope and probe the frequency of the SDCLK? Yes - see my post (above) about having a stock Jessie Lite Raspberry image without any device tree modification. Stock Jessie Lite: 41.67MHz, can mount/read/write mmcblk1p1 successfully tek00007.png Modified device tree: Switches between ...

What happens if you measure the frequency after increasing CPU load? Run cat /dev/urandom > /dev/null & to make some fake load. Interesting...I have my 'dtparam=i2c_baudrate=600000' set up in the /boot/config.txt , as previously posted. If I run the normal 'i2cdetect -y 1' (without your suggest...

Do you have external pull ups on the SD lines? Yes and no - I did originally (10k's as placeholders just in case) but I removed them as a test with the same result. Ditto with some ESD diodes - those two were actually the first thing I suspected. If signal integrity is suspected, it might be worth ...

I am also doing exactly what this thread is discussing - I have a CM3 (not CM3L) with GPIO22-27 hooked up to a (second) SD card interface. I've verified with 'gpio readall' that GPIO 22-27 are in ALT3 mode after adding 'dtoverlay=sdio,poll_once=off' to /boot/config.txt. After a reboot, I see this re...

I agree! I am running on the Raspberry Pi Compute Module 3, and I see the same thing (verified with a scope). I'm using I2C-bus 1: 100kHz - Actual = 62.5kHz 600kHz - Actual = 375kHz The '100' and '600' are changed values in /boot/config.txt, for example: dtparam=i2c_baudrate=100000 dtparam=i2c_baudr...