Serial over USB not working with raspberry pi zero

Question

This is really a Raspberry Pi Zero question more than a Jevois question, but I thought I'd ask it here since someone may have come across it already.

I have a python script that sends serial commands to the Jevois cam and gets video and serial responses via the USB connection. It works fine on windows, Ubuntu and on a Raspberry Pi 3B+.

It doesn't work on a Raspberry Pi Zero. It either hangs or crashes when the script writes to the serial port port depending on which device I use.

Any ideas?

One possible clue is that dmesg seems to show the Jevois being treated as an SD card.

Answer 1

Maybe you need an OTG cable? By default I guess the Pi Zero is a "device" (i.e., you would connect its microUSB to a regular USB port on a host computer). But you want it to operate as "host" here (and JeVois is your "device"), so the OTG cable might be what you need. See, eg,

https://raspberrypi.stackexchange.com/questions/84577/raspberry-pi-zero-w-connect-micro-usb-to-ftdi-to-arduino-board

just a thought but I don't have that hardware right now to test.

The OTG cable should go from microUSB that you plug into your PI Zero to a regular USB (type A) female. Then you would use a Y cable, connect one of the type A male to a power source, the other to your OTG female, and the mini-USB end to JeVois.

Like this: https://www.showmecables.com/micro-usb-2-b-male-to-a-female-6-in?gclid=CjwKCAiAqt7jBRAcEiwAof2uK-SYAzxasWY5hbg_EiiMZRcIuVxs8qRekFJfuDVqAiKWPb8oK2B4vxoChzMQAvD_BwE

Comments

Yeah, I have one of the OTG cables and was using it connect the Zero to the Jevois using the split USB power/signal cable that you guys supplied.

Your discussion of cables sparked an idea though. I have one of your USB to serial cables. As a first step, I can connect the Zero's USB port to the Jevois' serial port via the OSB and see if I can get them to communicate that way. If that works, I'll get a USB hub or Y so I can get both serial and video.
Thanks.

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oh, great, another thing is that maybe the device is not called /dev/ttyACM0

you should have a line about cdc_acm in your dmesg, see the dmesg snippet here: http://jevois.org/doc/USBserialLinux.html