UART on the HAT UP4000
I would like to use the UART on the HAT connector. I am having trouble getting a basic loopback test to work. I am using Ubuntu Server 22.04.
ls /sys/bus/pci/devices/0000:00:18.?/dw-apb-uart.*/tty/ | grep tty
/sys/bus/pci/devices/0000:00:18.0/dw-apb-uart.3/tty/:
ttyS4
/sys/bus/pci/devices/0000:00:18.1/dw-apb-uart.4/tty/:
ttyS5
Judging by the wiki, the HAT UART should be ttyS5, so to loopback I short the Tx and Rx and run:
sudo screen /dev/ttyS5 115200
But I get no returned chars. I tried on tty4 to be sure but again, no chars.
Further information on my system. ttyAMC0 and ttyUSB0 are known attached devices, they work OK:
sudo dmesg | grep tty
[ 0.132638] printk: console [tty0] enabled
[ 8.074938] cdc_acm 1-6:1.0: ttyACM0: USB ACM device
[ 8.094024] dw-apb-uart.3: ttyS4 at MMIO 0x91224000 (irq = 4, base_baud = 115200) is a 16550A
[ 8.124707] dw-apb-uart.4: ttyS5 at MMIO 0x91222000 (irq = 5, base_baud = 115200) is a 16550A
[ 8.140810] usb 1-5: FTDI USB Serial Device converter now attached to ttyUSB0
Hoping somebody can offer some advice on what else I can check, am I right in thinking ttyS5 is my port?
Answers
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This is resolved now.
Quite extreme but I started again and followed these wiki steps:
- Use Ubuntu Server 20.04
- Install the Upboard Kernel as the support for this is 20.04 https://github.com/up-board/up-community/wiki/Ubuntu_20.04
- Configure support for the GPIO header as per the wiki instructions https://github.com/up-board/up-community/wiki/Ubuntu_20.04
- Set the permissions with usermod for the UART
Now, I can use the UART on the GPIO header and access with Node-Red.