Question

我正在使用Adafruit的Circuit Playground Express，我正在使用Circuit Python进行编程。

我想读取从Circuit Playground Express通过USB连接的计算机传输的数据。使用input()工作正常，但我宁愿得到串口的缓冲区，这样循环就会继续，而没有输入。像serial.read()这样的东西。

import serial不适用于Circuit Python，或者我必须安装一些东西。我还能做些什么来使用Circuit Python读取串行缓冲区吗？

Answer 1

This is now somewhat possible! In the January stable release of CircuitPython 3.1.2 the function serial_bytes_available was added to the supervisor module.

This allows you to poll the availability of serial bytes.

For example in the CircuitPython firmware (i.e. boot.py) a serial echo example would be:

import supervisor

def serial_read():
   if supervisor.runtime.serial_bytes_available():
       value = input()
       print(value)

and ensure when you create the serial device object on the host side you set the timeout wait to be very small (i.e. 0.01).

i.e in python:

import serial

ser = serial.Serial(
             '/dev/ttyACM0',
             baudrate=115200,
             timeout=0.01)

ser.write(b'HELLO from CircuitPython\n')
x = ser.readlines()
print("received: {}".format(x))

Answer 2

显然，截至目前，这是不可能的。请参阅Adafruit here的完整讨论。

Answer 3

艾登的答案引导我朝着正确的方向发展，我在这里找到了一个很好的（略有不同）如何使用Adafruit的supervisor.runtime.serial_bytes_available的示例（具体来说是89-95行）：https://learn.adafruit.com/AT-Hand-Raiser/circuitpython-code

code.py的一个最小工作示例是输入，并以“ RX：string”格式设置新字符串的格式是

import supervisor

print("listening...")

while True:
    if supervisor.runtime.serial_bytes_available:
        value = input().strip()
        # Sometimes Windows sends an extra (or missing) newline - ignore them
        if value == "":
            continue
        print("RX: {}".format(value))

测试于：Adafruit CircuitPython 4.1.0 on 2019-08-02;带有samd21g18的Adafruit ItsyBitsy M0 Express。在macOS上通过mu-editor中的串行连接发送的消息。

样本输出

main.py output:
listening...
hello!
RX: hello!

Answer 4

基于上述帖子，我有一个简单的示例可以工作，不确定它是否稳定或有用，但仍在此处发布：

CircuitPython代码：

import supervisor

while True:
    if supervisor.runtime.serial_bytes_available:
        value = input().strip()
        print(f"Received: {value}\r")

PC代码

import time
import serial
ser = serial.Serial('COM6', 115200)  # open serial port

command = b'hello\n\r'
print(f"Sending Command: [{command}]")
ser.write(command)     # write a string

ended = False
reply = b''

for _ in range(len(command)):
    a = ser.read() # Read the loopback chars and ignore

while True:
    a = ser.read()

    if a== b'\r':
        break

    else:
        reply += a

    time.sleep(0.01)

print(f"Reply was: [{reply}]")

ser.close()

c:\circuitpythontest>python TEST1.PY
Sending Command: [b'hello\n\r']
Reply was: [b'Received: hello']

使用Circuit Playground Express上的Circuit Python从主机接收数据

4 个答案: