Dual USB serial and I2C converter

I did something similar, to debug the comms between the ESP8266 and the atmega32u4 on a cactus micro rev2 board. But I just hooked up two USB serial adapters with probes, I didn’t bother making a board for it :-)

I also wrote a trivial python program to read both serial ports and output them interleaved.

#!/usr/bin/python3

import serial, time, sys, threading
from colorama import Fore, Style, init as colorama_init

colorama_init()

# lock to serialize console output
lock = threading.Lock()

class Highlight:
def __init__(self, clazz, color):
self.color = color
self.clazz = clazz
def __enter__(self):
print(self.color, end=””)
def __exit__(self, type, value, traceback):
if self.clazz == Fore:
print(Fore.RESET, end=””)
else:
assert self.clazz == Style
print(Style.RESET_ALL, end=””)
sys.stdout.flush()

if len(sys.argv) != 3 and len(sys.argv) != 4:
sys.stderr.write(“Usage: %s []\n” % (sys.argv[0]))
exit(1)

def read_serial(port, baud, color):
ser = serial.Serial()
ser.port = port

ser.baudrate = baud
ser.bytesize = serial.EIGHTBITS #number of bits per bytes
ser.parity = serial.PARITY_NONE #set parity check: no parity
ser.stopbits = serial.STOPBITS_ONE #number of stop bits
#ser.timeout = None #block read
ser.timeout = 0 # non blocking read
ser.xonxoff = False #disable software flow control
ser.rtscts = False #disable hardware (RTS/CTS) flow control
ser.dsrdtr = False #disable hardware (DSR/DTR) flow control
ser.writeTimeout = 2 #timeout for write

try:
ser.open()
except Exception as e:
print(“error open serial port: ” + str(e))
exit()

if ser.isOpen():
try:
while True:
c = ser.read(size=1024)
with lock:
if len(c) > 0:
print(color)
sys.stdout.buffer.write(c)

ser.close()

except Exception as e1:
print (“error communicating…: ” + str(e1))

else:
print(“cannot open serial port “)
exit()

# Create two threads as follows
try:
t = threading.Thread(target=read_serial, args=(sys.argv[2], sys.argv[1], Fore.GREEN ))
t.daemon = True # thread dies when main thread (only non-daemon thread) exits.
t.start()

if len(sys.argv) == 4:
t = threading.Thread(target=read_serial, args=(sys.argv[3], sys.argv[1], Fore.RED ))
t.daemon = True # thread dies when main thread (only non-daemon thread) exits.
t.start()
except:
print(“Error: unable to start thread”)

try:
while True:
pass
except KeyboardInterrupt:
exit()