Troubleshooting • Trying to transmit/receive with connected radio module SR105U

Code:

import RPi.GPIO as GPIOimport serialimport time# Pin numbering setGPIO.setmode(GPIO.BOARD)GPIO.setwarnings(False)# Setup a channelchannel_ptt = 38channel_PD = 40  # 0: sleeping, 1: runningchannel_TXD = 8channel_RXD = 10###################### Setup()  ######################### Set PD Channel to run radio moduleGPIO.setup(channel_PD, GPIO.OUT, initial=GPIO.HIGH)# Set PTT Channel as an input# GPIO.LOW: Transmit# GPIO.HIGH: ReceiveGPIO.setup(channel_ptt, GPIO.OUT, initial=GPIO.LOW)# Serial Setup# Open serial portser = serial.Serial('/dev/serial0', baudrate=9600, timeout=1)######################## Loop() #########################try:    while True:        GPIO.output(channel_PD, GPIO.LOW)        GPIO.output(channel_ptt, GPIO.LOW)        # Check if the GPIO values are set correctly        pd_state = GPIO.input(channel_PD)        ptt_state = GPIO.input(channel_ptt)        print(f"PD state: {'HIGH' if pd_state == GPIO.HIGH else 'LOW'}")        print(f"PTT state: {'HIGH' if ptt_state == GPIO.HIGH else 'LOW'}")        ser.write(b'\xAA\x55' * 50)        time.sleep(1)except KeyboardInterrupt:    print("Transmission stopped by user")finally:    ser.close()    GPIO.cleanup()