Binary data with pyserial(python serial port)

Question

serial.write() method in pyserial seems to only send string data. I have arrays like [0xc0,0x04,0x00] and want to be able to send/receive them via the serial port? Are there any

Answer 1

I faced a similar (but arguably worse) issue, having to send control bits through a UART from a python script to test an embedded device. My data definition was "field1: 8 bits , field2: 3 bits, field3 7 bits", etc. It turns out you can build a robust and clean interface for this using the BitArray library. Here's a snippet (minus the serial set-up)

from bitstring import BitArray

cmdbuf = BitArray(length = 50)     # 50 byte BitArray
cmdbuf.overwrite('0xAA', 0)       # Init the marker byte at the head

Here's where it gets flexible. The command below replaces the 4 bits at bit position 23 with the 4 bits passed. Note that it took a binary bit value, given in string form. I can set/clear any bits at any location in the buffer this way, without having to worry about stepping on values in adjacent bytes or bits.

cmdbuf.overwrite('0b0110', 23)

# To send on the (previously opened) serial port 
ser.write( cmdbuf )