Using UART on up board

Chris Polanco

hello,

I'm having issues with the UART as well I am using Ubuntu with the upboard kernel and i can't get mraa to work. everytime i run my program it gives me the following error:

File "motorController.py", line 8, in <module>
transmitter = mraa.Uart(1)
File "/usr/local/lib/python2.7/dist-packages/mraa.py", line 1181, in __init__
this = _mraa.new_Uart(*args)
ValueError: Error initialising UART

i've tried multiple numbers in mraa.Uart and none work. The Up-board wiki says to use ttyS1 for UART but when i run
dmesg | grep tty i get the following:

[ 0.000000] console [tty0] enabled
[ 1.123350] 00:01: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[ 3.555733] 8086228A:00: ttyS4 at MMIO 0xa171b000 (irq = 39, base_baud = 2764800) is a 16550A

ttyS1 isn't showing on here and I don't know if that's the issue or not. and if it is i'm not sure how to enable the port.

also, not sure if this is any help but when i run sudo cat /proc/tty/driver/serial i get the following.

serinfo:1.0 driver revision:
0: uart:16550A port:000003F8 irq:4 tx:0 rx:0
1: uart:unknown port:000002F8 irq:3
2: uart:unknown port:000003E8 irq:4
3: uart:unknown port:000002E8 irq:3
4: uart:16550A mmio:0xA171B000 irq:39 tx:0 rx:0
5: uart:unknown port:00000000 irq:0
6: uart:unknown port:00000000 irq:0
7: uart:unknown port:00000000 irq:0
8: uart:unknown port:00000000 irq:0
9: uart:unknown port:00000000 irq:0
10: uart:unknown port:00000000 irq:0
11: uart:unknown port:00000000 irq:0
12: uart:unknown port:00000000 irq:0
13: uart:unknown port:00000000 irq:0
14: uart:unknown port:00000000 irq:0
15: uart:unknown port:00000000 irq:0
16: uart:unknown port:00000000 irq:0
17: uart:unknown port:00000000 irq:0
18: uart:unknown port:00000000 irq:0
19: uart:unknown port:00000000 irq:0
20: uart:unknown port:00000000 irq:0
21: uart:unknown port:00000000 irq:0
22: uart:unknown port:00000000 irq:0
23: uart:unknown port:00000000 irq:0
24: uart:unknown port:00000000 irq:0
25: uart:unknown port:00000000 irq:0
26: uart:unknown port:00000000 irq:0
27: uart:unknown port:00000000 irq:0
28: uart:unknown port:00000000 irq:0
29: uart:unknown port:00000000 irq:0
30: uart:unknown port:00000000 irq:0
31: uart:unknown port:00000000 irq:0

I want to be able to communicate to my motor controller through serial but can't find out how it works. Any help will do. Thanks in advance.

Kurt

My guess from the other thread is you are using the generic kernel and not the one with UP stuff...

Chris Polanco

Updated the kernel to 4.4. Problem fixed. Thanks for your help.

Duncan Iglesias

Hey,

In my case, I am running Ubuntu 14.04 on the UP Board I found that the UART1 RX/TX pins 8 and 10 are actually ttyS4 and not ttyS1 as indicated by the GPIO pin out here:

https://software.intel.com/en-us/articles/robotics-development-kit-blink-led-tutorial

If you are using pins 8/10 for communication with your motor driver, make sure that you read/write to /dev/ttyS4 using sudo privileges or running as root (sudo su).

Good luck!

Duncan