implement BPSK modulation (tx-only with arbitrary freq setting)

src/main.rs

@@ -1,7 +1,7 @@
 #![no_std]
 #![no_main]
 
-use defmt::{error, info, warn};
+use defmt::{error, info};
 use embassy_executor::Spawner;
 use embassy_stm32::{
     Config,
@@ -11,11 +11,12 @@ use embassy_stm32::{
 };
 use embassy_time::{Duration, Timer};
 use stm32wle5jc_radio::{
-    RadioError,
-    modulations::lora::{Bandwidth, LoraConfig, LoraRadio, SpreadingFactor},
+    modulations::
+        bpsk::{Bitrate, BpskConfig, BpskRadio}
+    ,
     radio::{PaSelection, Radio},
     spi::SubGhzSpiDevice,
-    traits::{Configure, Receive, Transmit},
+    traits::{Configure, Transmit},
 };
 use {defmt_rtt as _, panic_probe as _};
 
@@ -37,32 +38,23 @@ async fn main(_spawner: Spawner) {
     let mut radio = Radio::new(spi, rf_tx, rf_rx, rf_en);
     radio.init().await.unwrap();
 
-    let mut lora = LoraRadio::new(&mut radio);
-    lora.configure(&LoraConfig {
+    let mut bpsk = BpskRadio::new(&mut radio);
+    bpsk.configure(&BpskConfig {
         frequency: 868_100_000,
-        sf: SpreadingFactor::SF9,
-        bw: Bandwidth::Bw7_8kHz,
+        bitrate: Bitrate::Bps600,
         pa: PaSelection::HighPower,
-        power_dbm: 22,
+        power_dbm: 17,
         ..Default::default()
     })
     .await
     .unwrap();
 
     info!("sending stuffs");
-    match lora.tx(b"hiiiiiII!").await {
+    match bpsk.tx(b"hiiiiiII!").await {
         Ok(_) => info!("yay :3"),
         Err(e) => error!("tx error: {:?}", e),
     }
 
-    info!("waiting for packet...");
-    let mut buf = [0u8; 255];
-    match lora.rx(&mut buf, 1_000).await {
-        Ok(len) => info!("rx {} bytes: {:x}", len, &buf[..len]),
-        Err(RadioError::Timeout) => warn!("no packet received (timeout)"),
-        Err(e) => error!("rx error: {:?}", e),
-    }
-
     loop {
         Timer::after(Duration::from_secs(1)).await;
     }

src/modulations/bpsk.rs

@@ -0,0 +1,152 @@
+use defmt::debug;
+use embedded_hal::digital::OutputPin;
+use embedded_hal_async::spi::SpiDevice;
+
+use crate::{RadioError, radio::{PaSelection, PacketType, Radio, RampTime, irq}, traits::{Configure, Transmit}};
+
+/// BPSK bitrate
+/// Formula: register = (32 * 32_000_000) / bps
+#[derive(Clone, Copy, defmt::Format)]
+pub enum Bitrate {
+    /// 100 bits per second
+    Bps100,
+    /// 600 bits per second
+    Bps600,
+    /// Arbitrary bitrate in bits per second
+    Custom(u32),
+}
+
+impl Bitrate {
+    /// Get the 3-byte register value for this bitrate
+    fn to_bytes(self) -> [u8; 3] {
+        let val = match self {
+            Bitrate::Bps100 => 0x9C4000,
+            Bitrate::Bps600 => 0x1A0AAA,
+            Bitrate::Custom(bps) => (32 * 32_000_000) / bps,
+        };
+        [(val >> 16) as u8, (val >> 8) as u8, val as u8]
+    }
+}
+
+#[derive(Clone, Copy, defmt::Format)]
+pub struct BpskConfig {
+    pub frequency: u32,
+    pub bitrate: Bitrate,
+    pub pa: PaSelection,
+    pub power_dbm: i8,
+    pub ramp: RampTime,
+}
+
+impl Default for BpskConfig {
+    fn default() -> Self {
+        Self {
+            frequency: 868_100_000,
+            bitrate: Bitrate::Bps600,
+            pa: PaSelection::LowPower,
+            power_dbm: 14,
+            ramp: RampTime::Us40,
+        }
+    }
+}
+
+/// BPSK modulation - borrows a Radio, implements Configure + Transmit
+pub struct BpskRadio<'a, SPI: SpiDevice, TX: OutputPin, RX: OutputPin, EN: OutputPin> {
+    radio: &'a mut Radio<SPI, TX, RX, EN>,
+    payload_len: u8,
+    config: BpskConfig,
+}
+
+impl<'a, SPI: SpiDevice, TX: OutputPin, RX: OutputPin, EN: OutputPin>
+    BpskRadio<'a, SPI, TX, RX, EN>
+{
+    pub fn new(radio: &'a mut Radio<SPI, TX, RX, EN>) -> Self {
+        Self {
+            radio,
+            payload_len: 0,
+            config: BpskConfig::default(),
+        }
+    }
+
+    /// Re-send SetPacketParams with updated payload length (called before each tx/rx)
+    async fn update_payload_len(&mut self, len: u8) -> Result<(), RadioError> {
+        debug!("Updating payload length to {}", len);
+        if len == self.payload_len {
+            return Ok(());
+        }
+        self.payload_len = len;
+        self.send_packet_params(len).await
+    }
+
+    /// Send the full SetPacketParams command with the given payload length
+    async fn send_packet_params(&mut self, payload_len: u8) -> Result<(), RadioError> {
+        self.radio
+            .set_packet_params(&[payload_len])
+            .await
+    }
+}
+
+impl<SPI: SpiDevice, TX: OutputPin, RX: OutputPin, EN: OutputPin> Configure
+    for BpskRadio<'_, SPI, TX, RX, EN>
+{
+    type Config = BpskConfig;
+
+    async fn configure(&mut self, config: &Self::Config) -> Result<(), RadioError> {
+        self.config = *config;
+
+        // Select BPSK packet type
+        self.radio.set_packet_type(PacketType::Bpsk).await?;
+
+
+        // Payload length updated per tx
+        self.send_packet_params(0).await?;
+
+        // RF frequency
+        self.radio.set_rf_frequency(config.frequency).await?;
+
+        // Set modulation params (bitrate + Gaussian BT 0.5 pulse shape)
+        let br = config.bitrate.to_bytes();
+        self.radio
+            .set_modulation_params(&[br[0], br[1], br[2], 0x16])
+        .await?;
+
+        // PA config + TX power
+        self.radio
+            .set_output_power(config.pa, config.power_dbm, config.ramp).await?;
+
+        Ok(())
+    }
+}
+
+impl<SPI: SpiDevice, TX: OutputPin, RX: OutputPin, EN: OutputPin> Transmit
+    for BpskRadio<'_, SPI, TX, RX, EN>
+{
+    async fn tx(&mut self, data: &[u8]) -> Result<(), RadioError> {
+        if data.len() > 255 {
+            return Err(RadioError::PayloadTooLarge);
+        }
+
+        // Write payload to radio buffer
+        self.radio.set_buffer_base(0x00, 0x00).await?;
+        self.radio.write_buffer(0x00, data).await?;
+
+        // Update packet params with actual payload length
+        self.update_payload_len(data.len() as u8).await?;
+
+        // Clear any stale IRQ flags before starting TX
+        self.radio.clear_irq(irq::ALL).await?;
+
+        // Enable TxDone IRQ on DIO1
+        self.radio.set_dio1_irq(irq::TX_DONE | irq::TIMEOUT).await?;
+
+        // Start TX
+        self.radio.set_tx(0).await?;
+
+        // Wait until it's done or until timeout
+        let status = self.radio.poll_irq(irq::TX_DONE | irq::TIMEOUT).await?;
+        if status & irq::TIMEOUT != 0 {
+            return Err(RadioError::Timeout);
+        }
+
+        Ok(())
+    }
+}

src/modulations/mod.rs

@@ -1 +1,2 @@
+pub mod bpsk;
 pub mod lora;