I am trying to log in to my CM3 running the latest raspbian stretch-lite image (found here: https://www.raspberrypi.org/downloads/raspbian/ ) through the UART. My understanding is that UART0 is the more powerful one as it is not tied to the core clock, and for now this would be the better choice, but I can't seem to get either to work.
I have followed some guides for this including https://learn.adafruit.com/adafruits-ra ... al-console however, most resources I have been able to find have been targeted towards the RPi3 which I understand occupies the UART0 with its BT module so the process is a bit different.
Here is exactly what I have done using Raspberry Pi Compute Module 3 version 1.0, Compute Module IO Board V3.0:
- followed these instructions to flash the emmc with the latest raspbian stretch image: https://www.raspberrypi.org/documentati ... lashing.md
- added "enable_uart=1" to /boot/config.txt (to my knowledge, this step is the same as enabling serial console in raspi-config)
- verified that /boot/cmdline.txt includes the following phrase: "console=ttyS0,115200"
- Connected my host machine to a ftdi breakout board configured to use 3.3v logic: https://www.sparkfun.com/products/9716
- Connected RXI from ftdi board to the pin labelled 14 on the CMIO board
- Connected TXO from ftdi board to pin labelled 15 on the CMIO board
- Connected GND from ftdi board to a GND pin on the CMIO board
- booted the cm3 with the USB SLAVE BOOT jumpered to the disabled position
- ran sudo screen /dev/ttyUSB0 115200 on my host machine and hit enter.
I have been trying to solve this issue on my own with the following attempted solutions:
- verified with scope that ftdi board works properly
- flip tx and rx pins
- use pins 32 and 33 instead of 14 and 15
- replace "enable_uart=1" with "dtoverlay=uart1" and "core-freq=250"
- logging in locally and running raspi-config to turn serial console on
- recompiled the linux kernel and device tree modules following the instructions found here: https://www.raspberrypi.org/documentati ... ilding.md
- replacing "enable_uart=1" with "dtoverlay=uart0"
Does anybody have any ideas? Am I missing something crucial here? I am not super familiar with linux so I wouldn't be surprised if I was. Could I be misinterpreting how screen is supposed to work or what the "serial console" means entirely?
Any help is much appreciated.