大家好，我在使用树莓派4B的串口通信，按照网上例程在这个位置会报
s = fcntl.ioctl(self.fd, TIOCINQ, TIOCM_zero_str)
OSError: [Errno 25] Inappropriate ioctl for device，提示没有找到设备，对应的语句是
data_left = ser.inWaiting()
整个代码如下：
```
import serial
import time

# 打开串口
ser = serial.Serial("/dev/ttyAMA0", 9600)


def main():
while True:


data_left = ser.inWaiting() # check for remaining byte
received_data += ser.read(data_left)
print(received_data) # print received data
ser.write(received_data)
received_data = ser.read() # read serial port
sleep(0.03)
```