MicroPython • Interfacing raspberry pi pico with sim808 to send and receive messages

Code:

from machine import UART, Pingsm_module = UART(1, baudrate=9600, tx=Pin(4), rx=Pin(5), timeout=2000)gsm_buffer = ''destination_phone = '+918830584864'relay1 = Pin(2, Pin.OUT)relay2 = Pin(3, Pin.OUT)def convert_to_string(buf):    tt =  buf.decode('utf-8').strip()    return ttdef do_action(msg):    msg = msg.lower()    if(msg.strip() == 'light off'):        relay1(0)        send_sms('light is OFF')    elif(msg.strip() == "light on"):        relay1(1)        send_sms('light is ON')    elif(msg.strip() == 'fan off'):        relay2(0)        send_sms('fan is OFF')    elif(msg.strip() == 'fan on'):        print('do_action1: '+msg)        relay2(1)        send_sms('fan is ON')def send_command(cmdstr, lines=1, msgtext=None):    global gsm_buffer    print(cmdstr)    cmdstr = cmdstr+'\r\n'        while gsm_module.any():        gsm_module.read()        gsm_module.write(cmdstr)        if msgtext:        print(msgtext)        gsm_module.write(msgtext)     buf=gsm_module.readline()     buf=gsm_module.readline()    if not buf:        return None    result = convert_to_string(buf)        if lines>1:        gsm_buffer = ''        for i in range(lines-1):            buf=gsm_module.readline()            if not buf:                return result            buf = convert_to_string(buf)            if not buf == '' and not buf == 'OK':                gsm_buffer += buf+'\n'        return resultdef read_sms(sms_id):    result = send_command('AT+CMGR={}\n'.format(sms_id),99)    print(result)        if result:        params=result.split(',')        if params[0] == '':           return None                params2 = params[0].split(':')        if not params2[0]=='+CMGR':            return None                number = params[1].replace('"',' ').strip()        date   = params[3].replace('"',' ').strip()        time   = params[4].replace('"',' ').strip()        #print('gsm_buffer:'+gsm_buffer)        return  [number,date,time,gsm_buffer]      def send_sms(msgtext):    global gsm_buffer    result = send_command('AT+CMGS="{}"\n'.format(destination_phone),99,msgtext+'\x1A')    if result and result=='>' and gsm_buffer:        params = gsm_buffer.split(':')        if params[0]=='+CUSD' or params[0] == '+CMGS':            print('OK')            return 'OK'    print('ERROR')    return 'ERROR'print(send_command('AT'))print(send_command('AT+CMGF=1'))print(send_command('AT+CNMI=1'))while True:    if gsm_module.any():        buf=gsm_module.readline()        buf = convert_to_string(buf)        print(buf)                params=buf.split(',')              if params[0][0:5] == "+CMTI":            msgid = int(params[1])            msg_data = read_sms(msgid)                        if not msg_data:                print("No sms data found.")                break                      print(msg_data[3])                        if not msg_data[0] == destination_phone:                print("Destination phone pumber not matching")                break                       do_action(msg_data[3]            )