Score:0

Not receiving serial data through Raspberry Pi UART

cn flag

I'm trying to connect a Pi Pico to my Raspberry Pi 4, running Ubuntu Server 21.04, via serial UART. I know the pins and connections are correct because the same connection works perfectly on a Raspbian install. On Ubuntu, however, I simply don't receive anything when I run picocom /dev/ttyS0.

My /boot/firmware/cmdline.txt:

dwc_otg.lpm_enable=0 console=tty1 root=LABEL=writable rootfstype=ext4 elevator=deadline rootwait fixrtc quiet splash

My /boot/firmware/config.txt:

[...]
# Enable the serial pins
enable_uart=1
[...]

The device is owned by the tty group, which I am part of:

ubuntu@ada:~$ ls -la /dev/ttyS0
crw-rw---- 1 root tty 4, 64 Dec  8 01:10 /dev/ttyS0
ubuntu@ada:~$ groups
ubuntu adm tty dialout cdrom floppy sudo audio dip video plugdev bluetooth netdev lxd

I've disabled [email protected].

I've rebooted (lots!).

What am I missing?

Score:1
cn flag

The culprit turned out to be this particular Raspberry Pi Pico, which seems to have a flaky or unreliable UART pin. The above is, for what it's worth, a good summary of how to set up Ubuntu on the Raspberry Pi for UART communication!

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