Python script for tuning rtl_fm using input from WxToImg

kenwood.py

#!/usr/bin/python3

import serial
import socket
import time
import subprocess


"""
DC0;SQ0000;FA00137100000;MD4;FA00137102450;FA00137102440;FA00137102436;...
Sent over serial by WxToImg for doppler tuning if below is set;

Options > Recording Options >
receiver type = Kenwood
receiver port = /dev/ttyAMA0
receiver baud rate = 9600

Short Raspberry Pi UART TXD/RXD pins together
"""


IN_DEV = "/dev/ttyAMA0"
BAUD = 9600
END_MSG = ";"
RTL_RATE = "60k"


class rtl_fm_remote(object):
    """
    For remote control of rtl_fm command line program
    """
    def __init__(self,
                 host="localhost",
                 port=6020):
        self._host = host
        self._port = port
        self._s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        self._s.connect((self._host, self._port))

    def set_freq(self, freq):
        self.send_cmd(0, freq)

    def set_mode(self, mode):
        self.send_cmd(1, mode)

    def set_squelch(self, squelch):
        self.send_cmd(2, squelch)

    def set_gain(self, gain):
        self.send_cmd(3, gain)

    def send_cmd(self, cmd, param):
        cmd_bytes = (cmd).to_bytes(1, "little")
        param_bytes = (param).to_bytes(32, "little")
        self._s.send(cmd_bytes + param_bytes)

    def __del__(self):
        self._s.close()


rtl_proc = None
play_proc = None
rtl_remote = None
last_rx_time = 0

ser = serial.Serial(port=IN_DEV, baudrate=BAUD)
buffer = ""
rx_freq = 0

while True:
    time.sleep(.1)
    buffer += ser.read(ser.inWaiting()).decode("UTF8")
    if END_MSG in buffer:
        lines = buffer.split(END_MSG)
        buffer = ""
        for line in lines:
            if len(line) > 0 and line.startswith("FA"):
                str_freq = line[2:]
                if str_freq.isnumeric():
                    last_rx_time = time.time()
                    rx_freq = int(str_freq)

                    if rtl_proc is None:
                        rtl_cmd = ["rtl_fm", "-M", "fm", "-f", str(rx_freq), "-s", RTL_RATE, "-E", "deemp", "-F", "9"]
                        play_cmd = ["play", "-r", RTL_RATE, "-t", "raw", "-e", "s", "-b", "16", "-c", "1", "-V1", "-"]
                        rtl_proc = subprocess.Popen(rtl_cmd, stdout=subprocess.PIPE)
                        time.sleep(1)
                        play_proc = subprocess.Popen(play_cmd, stdin=rtl_proc.stdout)
                        time.sleep(1)
                        rtl_remote = rtl_fm_remote()
                    else:
                        rtl_remote.set_freq(rx_freq)

    if rtl_proc is not None:
        if time.time() - last_rx_time > 60:
            del(rtl_remote)
            rtl_remote = None
            play_proc.kill()
            play_proc.wait()
            play_proc = None
            rtl_proc.kill()
            rtl_proc.wait()
            rtl_proc = None