Raspberry Pi Forums

Hi All,

I have installed ubuntu on raspberry pi 4. I want pi to read data from the serial port. I am connecting the Tx, RX, GND pins from serial to Rx, Tx, GND respectively on the raspberry pi. But I am not able to read the data on ttyS0. Is it the right way to do it or do I have to make any other changes? It would be of great help if someone can help me out. Thank you.

You did follow this guide or similar?

When ubuntu acts similar as raspbian you can check several things.

cat /dev/ttyUSB1
ls -l /dev/ttyUSB* to find your devices
or lsusb to get some info

so in your case
cat /dev/ttyS0
ls -l /dev/ttyS0 to find your devices

when I run "ls -l /dev/ttyS0", this is what I get. Also, I have added username to group tty
crwxrwxrwx 1 root tty 4, 64 May 5 00:30 /dev/ttyS0.
but still, I am unable to read from the serial.

Also, this is what I get when I try to read the active serial ports on pi
$dmesg | grep tty
[ 0.000000] Kernel command line: coherent_pool=1M 8250.nr_uarts=1 cma=64M bcm2708_fb.fbwidth=0 bcm2708_fb.fbheight=0 bcm2708_fb.fbswap=1 smsc95xx.macaddr=DC:A6:32:68:09:94 vc_mem.mem_base=0x3ec00000 vc_mem.mem_size=0x40000000 net.ifnames=0 dwc_otg.lpm_enable=0 console=ttyS0,115200 console=tty1 root=LABEL=writable rootfstype=ext4 elevator=deadline rootwait fixrtc
[ 0.000531] printk: console [tty1] enabled
[ 3.127417] fe201000.serial: ttyAMA0 at MMIO 0xfe201000 (irq = 19, base_baud = 0) is a PL011 rev2
[ 3.128693] printk: console [ttyS0] disabled
[ 3.128728] fe215040.serial: ttyS0 at MMIO 0x0 (irq = 22, base_baud = 62500000) is a 16550
[ 4.701601] printk: console [ttyS0] enabled

I tried following the same link you sent me, but I couldn't find /boot/cmdline.txt on ubuntu to configure the pi.

HvdW wrote: ↑

Tue May 05, 2020 12:06 am

You did follow this guide or similar?

When ubuntu acts similar to raspbian you can check several things.
couldn't
cat /dev/ttyUSB1
ls -l /dev/ttyUSB* to find your devices
or lsusb to get some info

so in your case
cat /dev/ttyS0
ls -l /dev/ttyS0 to find your devices

Why do you prefer Ubuntu over raspbian?
It's there a special need?
Raspbian is very well documented and I haven't met any challenge that raspbian cannot cope with.
@home I'm running raspbian on RPI and Ubuntu on AMD64.