Last modified: Nov, 2013
This is a brief tutorial on how to use a Startech serial-to-USB adapter in Ubuntu. The procedure can be extended to other similar products.
First, find the product ID and vendor ID with the command
lsusb
For example, the line below
Bus 005 Device 002: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
means the vendor ID is 067b, and product ID is 2303.
To use the device in userspace, create a udev rule such as ‘/etc/udev/rules.d/90-usbserial.rules’ with the content like
SYSFS{idVendor}=="067b", SYSFS{idProduct}=="2303", RUN+="/sbin/modprobe usbserial vendor=0x067b product=0x2303", OPTIONS+="last_rule"
And then restart the udev daemon:
sudo restart udev
The following is an example of using Python to write to the serial port:
#!/usr/bin/env python
"""
Usage: python rs232_write.py "*RST"
"""
import serial
import sys
def serial_write(cmd, port='/dev/ttyUSB0'):
ser = serial.Serial(port=port, baudrate=9600, parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_TWO, bytesize=serial.EIGHTBITS)
if not ser.isOpen():
ser.open()
ser.write(cmd + '\r\n')
ser.close()
if __name__ == '__main__':
serial_write(sys.argv[1])If the device is still not writeable (error message like “no permission to write”), add the user to the group where “/dev/ttyUSB*” is in.