code.octet-stream.net Git - m17rt/blob - m17app/src/rtlsdr.rs

   1 use std::{
   2     io::Read,
   3     process::{Child, Command, Stdio},
   4     sync::{mpsc::SyncSender, Mutex},
   5 };
   6
   7 use crate::{
   8     error::M17Error,
   9     soundmodem::{InputSource, SoundmodemEvent},
  10 };
  11
  12 pub struct RtlSdr {
  13     frequency_mhz: f32,
  14     device_index: usize,
  15     rtlfm: Mutex<Option<Child>>,
  16 }
  17
  18 impl RtlSdr {
  19     pub fn new(device_index: usize, frequency_mhz: f32) -> Result<Self, M17Error> {
  20         Ok(Self {
  21             device_index,
  22             frequency_mhz,
  23             rtlfm: Mutex::new(None),
  24         })
  25     }
  26 }
  27
  28 impl InputSource for RtlSdr {
  29     fn start(&self, tx: SyncSender<SoundmodemEvent>) {
  30         // TODO: error handling
  31         let mut cmd = Command::new("rtl_fm")
  32             .args([
  33                 "-E",
  34                 "offset",
  35                 "-f",
  36                 &format!("{:.6}M", self.frequency_mhz),
  37                 "-d",
  38                 &self.device_index.to_string(),
  39                 "-s",
  40                 "48k",
  41             ])
  42             .stdout(Stdio::piped())
  43             .spawn()
  44             .unwrap();
  45         let mut stdout = cmd.stdout.take().unwrap();
  46         let mut buf = [0u8; 1024];
  47         let mut leftover: Option<u8> = None;
  48         std::thread::spawn(move || {
  49             while let Ok(n) = stdout.read(&mut buf) {
  50                 let mut start_idx = 0;
  51                 let mut samples = vec![];
  52                 if let Some(left) = leftover {
  53                     if n > 0 {
  54                         samples.push(i16::from_le_bytes([left, buf[0]]));
  55                         start_idx = 1;
  56                         leftover = None;
  57                     }
  58                 }
  59                 for sample in buf[start_idx..n].chunks(2) {
  60                     if sample.len() == 2 {
  61                         samples.push(i16::from_le_bytes([sample[0], sample[1]]))
  62                     } else {
  63                         leftover = Some(sample[0]);
  64                     }
  65                 }
  66                 if tx
  67                     .send(SoundmodemEvent::BasebandInput(samples.into()))
  68                     .is_err()
  69                 {
  70                     break;
  71                 }
  72             }
  73         });
  74         *self.rtlfm.lock().unwrap() = Some(cmd);
  75     }
  76
  77     fn close(&self) {
  78         if let Some(mut process) = self.rtlfm.lock().unwrap().take() {
  79             let _ = process.kill();
  80         }
  81     }
  82 }