#!/usr/bin/env python3
# -*- coding:utf-8 -*-
import serial
import pycrc
import time
import json
import asyncio
# Define the serial port and baud rate
vUSB = "ttyUSB0"
ser = "/dev/" + str(vUSB)
baud = 9600
@service("modbus.readregisters")
def read_modbus_registers():
 """yaml
 name: Reads Modbus registers from a device (in app modbus4)
 """
 try:
 s = serial.Serial(ser, baud)
 cmd = [0x00, 0x03, 0x00, 0x40, 0x00, 0x01, 0x00, 0x00]
 crc = pycrc.ModbusCRC(cmd[0:6])
 cmd[6] = crc & 0xFF
 cmd[7] = crc >> 8
 log.error(f"Sending command list (for info): {cmd} to port {s}")
 s.write(cmd)
 asyncio.sleep(1) # gets a warning - time.sleep(1)
 count = s.inWaiting()
 if count != 0:
 rec_b = s.read(count)
 rec_list = list(rec_b)
 state_var = {
 "device": rec_list[0],
 "command": rec_list[1],
 "register": rec_list[3],
 "val": rec_list[4]
 }
 state_var_json = json.dumps(state_var)
 log.error(f"Pyscript app modbus4 - modbus.readregisters - variables: {state_var_json}")
 except Exception as e:
 log.error(f"An error occurred: {str(e)}")
 finally:
 if s.is_open:
 s.close()