RS485 Python

Technical Support
1

Hi everyone,

I am testing an RS485 communication on IMX7D

Communication from the point of view of signals is ok and I am able to transmit and receive;
However I have a problem in a python script regarding reading;

the test system is very simple : I have a microcontrol that sends data at reagular intervals and the script on the SOM that must read them;
the script is trivially this:

import serial
import serial.rs485

ser = serial.Serial(
               port="/dev/ttymxc1",
               baudrate = 9600,
               timeout=0)


ser.rs485_mode = serial.rs485.RS485Settings()

if (ser.isOpen() == True):
  ser.close()
ser.open()
ser.reset_input_buffer

ser.read(ser.inWaiting())

The problem is that until 4095 bytes have been received, there is nothing readable;
if I check with ser.inWaiting ()
I get 0 until I get 4095 and at that point I can read all the queued messages …

Anyone know how to fix?

2

Look like the problem can be solved disabling UART dma

3

Hello Manbiz,
what OS you are using and which version. Are you using a custom carrier board?
Can you then please share your device tree file.