How to send bytes to serial port in Python | Control KMtronic USB Relay board example

Spread the love

KMtronic USB Relay Controller - One Channel - BOX — KMtronic USB Relay Controller – One Channel – BOX

KMtronic USB Eight Channel Relay Controller

FIRST channel commands:
OFF command : FF 01 00 (HEX) or 255 1 0 (DEC)
ON command : FF 01 01 (HEX) or 255 1 1 (DEC)

(1) Verify Python Interpreter Availability with ‘helloworld.py’

#!/usr/bin/python

# Hello world python program

print "Hello World!";

(2) Create ‘kmtronic_usb_relay_test.py” file

(3) Copy and paste code:

#!/usr/bin/python
# Test KMtronic WEB Relay board

print "Test KMtronic USB Relay board";

import os
import time
import serial
import subprocess

from struct import pack, unpack, calcsize

# configure the serial connections 
# (the parameters differs on the device 
# you are connecting to)
ser = serial.Serial(
 port='/dev/ttyUSB0',
 baudrate=9600,
 stopbits=serial.STOPBITS_ONE,
 bytesize=serial.EIGHTBITS,
 parity=serial.PARITY_NONE
)

ser.isOpen()

channel = 0x01;

print "RELAY1_ON_COMMAND: 0xFF 0x01 0x01"
state = 0x01;
int_msg = [0xFF, channel, state]
byte_msg = map(chr, int_msg)
packet = pack('=ccc', *byte_msg)
ser.write(packet)

time.sleep(1)

print "RELAY1_OFF_COMMAND: 0xFF 0x01 0x00"
state = 0;
int_msg = [0xFF, channel, state]
byte_msg = map(chr, int_msg)
packet = pack('=ccc', *byte_msg)
 
ser.write(packet)
 
ser.close()