40pin IO Development

Experiment 05 - UART Output

Hardware Connection

Loopback test: connect TXD and RXD on the hardware, then run the test program to write and read. The expected result is that the read data equals the written data.

Hardware Connection: connect TXD and RXD directly with a jumper:

IMG_256

Software Operation

(1) Select bus number and chip select from the printed serial devices (among which /dev/ttyS0 is the system debug port, not recommended for testing unless you fully understand its function). For RDK X5, select /dev/ttyS1 and input the baud rate.

(2) Enter the user home directory and run:

  1. cd user
  2. sudo python3 ./test_serial.py
TOOL
#!/usr/bin/env python3

import sys
import signal
import os
import time

# Import python serial library
import serial
import serial.tools.list_ports

def signal_handler(signal, frame):
    sys.exit(0)

def serialTest():
    print("List of enabled UART:")
    os.system('ls /dev/tty[a-zA-Z]*')
    uart_dev= input("请输出需要测试的串口设备名:")

    baudrate = input("请输入波特率(9600,19200,38400,57600,115200,921600):")
    try:
        ser = serial.Serial(uart_dev, int(baudrate), timeout=1) # 1s timeout
    except Exception as e:
        print("open serial failed!\n")

    print(ser)

    print("Starting demo now! Press CTRL+C to exit")

    while True:
        test_data = "AA55"
        write_num = ser.write(test_data.encode('UTF-8'))
        print("Send: ", test_data)

        received_data = ser.read(write_num).decode('UTF-8')
        print("Recv: ", received_data)

        time.sleep(1)

    ser.close()
    return 0


if __name__ == '__main__':
    signal.signal(signal.SIGINT, signal_handler)
    if serialTest() != 0:
        print("Serial test failed!")
    else:
        print("Serial test success!")