read the R_WHO_AM_I register from a Harp device

readHarp.py

#!/usr/bin/python3 -u

import serial
import struct
import sys 

# set up the serial device

if len(sys.argv) > 1:
    deviceFile = sys.argv[1]
else:
    deviceFile = '/dev/ttyUSB0'

harp = serial.Serial(deviceFile, 115200)

# first send a command message

msgType = 1     # read
length = 0      # tmp
address = 0     # R_WHO_AM_I
port = 255      # this device
payloadType = 1 # uint8_t
payload = 0     # don't care
checksum = 0    # tmp

#cmd = [msgType, length, address, port, payloadType, payload, checksum]
cmd = [msgType, length, address, port, payloadType, checksum]   # no payload for a read?

length = len(cmd) - 2   # "the number of bytes after the field [Length]"
cmd[1] = length

checksum = 0 
for v in cmd:
    checksum += v
checksum = checksum % 256 
cmd[-1] = checksum

print("Sending Command:", cmd)

cmd = bytes(cmd)
harp.write(cmd)

# then observe the response

while True:
    result = harp.read(1)
    print(result)