I am using a Raspberry Pi 3 and the wind speed sensor SEN0483 (see https://wiki.dfrobot.com/RS485_Wind_Speed_Transmitter_SKU_SEN0483) which is connected by a USB to RS485 module.

I want to read the data send by the wind speed sensor using Python code. For this I use the following code (based on the provided code in C in the wiki):

import serial
import time

def addedCRC(buf, len):
crc = 0xFFFF
for pos in range(len):
crc ^= int.from_bytes(buf[pos], byteorder='big')
for i in range(8, 0, -1):
if (crc & 0x0001) != 0:
crc >>= 1
crc ^= 0xA001
else:
crc >>= 1
buf[len] = crc % 0x100
buf[len + 1] = crc // 0x100

def CRC16_2(buf, len):
crc = 0xFFFF
for pos in range(len):
crc ^= int.from_bytes(buf[pos], byteorder='big')
for i in range(8, 0, -1):
if (crc & 0x0001) != 0:
crc >>= 1
crc ^= 0xA001
else:
crc >>= 1
crc = ((crc & 0x00ff) << 8) | ((crc & 0xff00) >> 8)
return crc

def read_wind_speed(address):
serial_port = '/dev/ttyUSB0' # Anpassen je nach USB-Adapter-Anschluss
baud_rate = 9600
ser = serial.Serial(serial_port, baud_rate, timeout=1)

try:
COM = bytearray([address, 0x03, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00])
addedCRC(COM, 6)
ser.write(COM)
ret = False
wind_speed = 0

while not ret:
if ser.in_waiting > 0:
ch = ser.read(1)
if ch[0] == address:
data = ch
ch = ser.read(1)
if ch[0] == 0x03:
data += ch
ch = ser.read(1)
if ch[0] == 0x02:
data += ch
data += ser.read(4)
crc = CRC16_2(data, 5)
if crc == (data[5] * 256 + data[6]):
ret = True
wind_speed = (data[3] * 256 + data[4]) / 10.0

except serial.SerialException as e:
print('serial error:', e)

ser.close()
return wind_speed

sensor_address = 0x01

wind_speed = read_wind_speed(sensor_address)
if wind_speed != 0:
print('wind speed:', wind_speed, 'm/s')
else:
print('error')

The code does not work as I obtain “error”.

Is there any Python code provided already for this sensor or does anyone have a working code to read the wind speed with Python?

Thank you in advance!