Python • Python serial programing

Code:

 import serialimport signalimport sysimport time# Serial port configurationPORT = "/dev/serial0"  # Use 'serial0' port instead of 'ttyS0'BAUDRATE = 19200       # Set baud rate to 19200 bps# Interrupt handler function (Ctrl+C)def signal_handler(sig, frame):    print("\nClosing program.")    if ser.is_open:        ser.close()    sys.exit(0)# Register interrupt handler for Ctrl+Csignal.signal(signal.SIGINT, signal_handler)try:    # Open serial port    ser = serial.Serial(PORT, BAUDRATE, timeout=1)    print(f"Connected to serial port {PORT} at baud rate {BAUDRATE}.")    # Echo control variable    echo_enabled = True    while True:        # Check if data is available on the serial port        if ser.in_waiting > 0:            # Decode the line using latin-1 encoding            line = ser.readline().decode('latin-1').strip()                        # Debugging - display the received line            print(f"Received: {line}")            # Echo handling            if echo_enabled:                ser.write((line + "\r\n").encode('latin-1'))            # AT command interpretation            if line == "AT":                ser.write(b"OK\r\n")  # Connection acknowledgment                print("Response: OK")            elif line == "ATE0":  # Disable echo                echo_enabled = False                ser.write(b"OK\r\n")                print("Response: OK (Echo disabled)")            elif line == "ATE1":  # Enable echo                echo_enabled = True                ser.write(b"OK\r\n")                print("Response: OK (Echo enabled)")            elif line == "AT+CGMM":  # Command to get model name                ser.write(b"C35i\r\n")                time.sleep(0.1)  # Short delay for older devices                print("Response: C35i")                        elif line.startswith("AT+CMGS="):  # Sending SMS                # Ready for receiving PDU data                ser.write(b"> ")                print("Response: > (Ready for PDU input)")                                # Wait for PDU data                pdu_data = ""                while True:                    if ser.in_waiting > 0:                        # Read the next PDU line                        pdu_line = ser.readline().decode('latin-1').strip()                        data = ser.readline()  # Read a single line                        print(data.decode('latin-1').strip())                        # Check if it's the end (Ctrl+Z) - ASCII code 26                        if pdu_line == chr(26):                            break  # End PDU data reception                                                # Add the PDU line to the data                        pdu_data += pdu_line                # Save PDU data to sms.dat file                with open("sms.dat", "a") as file:                    file.write(f"{pdu_data}\n")                                print(f"SMS saved to sms.dat: {pdu_data}")                                # Acknowledge receipt and send SMS                ser.write(b"\r\n+CMGS: 1\r\n")  # Sent SMS ID                ser.write(b"OK\r\n")                print("Response: +CMGS: 1, OK")                        else:                #ser.write(b"ERROR\r\n")                print("Response: ERROR - unknown command")except serial.SerialException as e:    print(f"Serial port error: {e}")finally:    if ser.is_open:        ser.close()

Code:

 Response: OK (Echo off)Received: AT+CMGS=75Response: > (Ready to receive PDU)SMS saved to sms.dat:Response: +CMGS: 1, OKReceived:--------------this is where the first read ends, but PDU is missing----------------on the next line, there is first SMS PDU data, but it only appears when the second SMS is sent, though as you can see, the PDU of the second SMS doesn’t appear despite the messages indicating it was received-----------------------------------------------------------------------------------0011PDU DATA PDU DATA PDU DATA 00000000ATE0Response: ERROR - unknown command——second SMS——Received: ATE0Response: OK (Echo off)Received: AT+CMGS=75Response: > (Ready to receive PDU)SMS saved to sms.dat:Response: +CMGS: 1, OK