Posts: 15
Joined: Tue Apr 04, 2017 11:39 pm

CM3s that die

Fri Jan 05, 2018 10:24 pm

We are experiencing a small number of CM3 modules that seem to 'go haywire' somehow when being programmed and will exhibit progressively worsening symptoms:

1. HDMI output starts to fail
2. HDMI output ceases to function (composite seems to work)
3. HDMI can't fetch EDID information anymore (tvservice -d foo.edid reports "no data written!" or similar)
2. CM3 stops booting
3. Powering the CM3 (even in a dev kit) causes the bcm2837 to get *really* hot *really* fast

We are flashing the CM3 using dcfldd similar to this:

`dcfldd sizeprobe=if bs=4M if=sd/20171215.1.img of=/dev/sdb `

Some basics about our setup -
a. We split emmc into 4 partitions, /boot / /data1 /data2
b. Linux 4.9.something'ish
c. /boot vfat, root is ext 4
d. all file systems are normally mounted read-only, there are a few configuration steps during production where /boot and/or / may be rw for a couple file operations.

We use our own carrier board. The CM3 is dead in both that and the CM3IO boards.

I suspect that during some of the configuration steps (d - above) the /boot partition is getting messed up. My suspicion originates in observing , in some instances, that if a file change happens on /boot and then the system is rebooted without 'sync' and `mount /boot -o remount,ro` then the system will be stuck shutting down for a long time, like several minutes (Normal reboot cycle time is about 15-20 seconds).

Once one of these 'long reboot' events occurs, the CM3 is usually toast.

To that end, I have compared all files in /boot on a 'bad' CM3 with a good one and see no differences (diff -q shows nothing).

I am working on imaging the entire MMC and am trying to compare against the flashed image.

Looking for any ideas about how to analyze this further... thoughts? suggestions?

Posts: 6
Joined: Sat Jun 17, 2017 11:38 pm

Re: CM3s that die

Sat Jan 27, 2018 6:56 am

I'd be looking at the power supply and interface on your carrier board.

Are the power lines filtered and not susceptible to spikes? Do they power the CM in the correct order? What about static protection both during installation, general handling and during cable connect / disconnect processes?

Do the CM recover after a re-flashing??

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