licheepi 4a串口通信(usb 串口)

博主使用usb串口原因是博主的是内测版本，虽然购买了1.8转3v3的usb转ttl模块，但是板载的UART1还是1.8V电平。所以本博客记录博主使用usb转串口进行串口通信。
博主环境：debian20231023镜像 lichee pi 4a 8+8G

（1）安装pyserial库并查看usb串口模块端口

安装pyserial库

pip3 install pyserial
pip list查看

博主终端输出信息：可以看到pyserial已经安装上去了

(ort) root@lpi4a:/home/sipeed/Desktop/udisk/test_py# pip list
Package                Version
---------------------- --------------------------------
certifi                2023.7.22
charset-normalizer     3.3.1
coloredlogs            15.0.1
cycler                 0.12.1
filelock               3.12.4
flatbuffers            23.5.26
fonttools              4.43.1
hhb-onnxruntime-th1520 2.6.0
humanfriendly          10.0
idna                   3.4
Jinja2                 3.1.2
kiwisolver             1.4.4
loguru                 0.7.0
MarkupSafe             2.1.3
matplotlib             3.7.2.dev0+gb3bd929cf0.d20230630
mpmath                 1.3.0
networkx               3.2
numpy                  1.25.0
opencv-python          4.5.4+4cd224d
packaging              23.2
Pillow                 9.5.0
pip                    23.0.1
protobuf               4.24.4
psutil                 5.9.5
pycocotools            2.0.6
pyparsing              3.1.1
pyserial               3.5
python-dateutil        2.8.2
requests               2.31.0
setuptools             66.1.1
setuptools-scm         8.0.4
six                    1.16.0
sympy                  1.12
tabulate               0.9.0
torch                  2.0.0a0+gitc263bd4
torchvision            0.15.1a0
tqdm                   4.65.0
typing_extensions      4.8.0
urllib3                2.0.7

查看usb串口模块端口
（博主的串口模块那么就是/dev/serial/by-id/usb-1a86_USB_Serial-if00-port0）

root@lpi4a:~# ls /dev/serial/by-id/
usb-1a86_USB_Serial-if00-port0

（2）程序与实测

# -*- coding: utf-8 -*-
import serial
import time
import threading
# 打开串口
serialPort = "/dev/serial/by-id/usb-1a86_USB_Serial-if00-port0"  # 串口
baudRate = 115200  # 波特率
ser = serial.Serial(serialPort, baudRate, timeout=0.5)
# ser = serial.Serial('/dev/serial/by-id/usb-1a86_USB_Serial-if00-port0', 115200)

def receive_message_wxw():
    global ser
    while True:
        data_count = ser.inWaiting()
        if data_count != 0:
            recv = ser.read(ser.in_waiting).decode("utf-8")
            print(recv)
tmp1 = threading.Thread(target=receive_message_wxw)
tmp1.start()
# 收发数据
while True:
    # str = input("请输入要发送的数据（非中文）并同时接收数据: ")
    str="test message\n"
    ser.write((str).encode('utf-8'))
    time.sleep(1);