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implement a BPSK decoder for demodulated data, add hal feature for use on non-STM32 targets

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Lukrecja Pleskaczyńska
2026-02-28 23:20:42 +01:00
parent 91a9b4a311
commit dc09b33d95
4 changed files with 218 additions and 54 deletions
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54
Cargo.toml
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@@ -15,36 +15,38 @@ members = ["examples/stm32wle5jc"]
# Default chip for development/CI. Downstream users should use default-features = false
# and enable their specific chip feature.
default = ["stm32wle5jc"]
# Hardware abstraction layer — enables embedded radio driver and all hardware deps
hal = ["dep:embassy-stm32", "dep:embassy-time", "dep:defmt", "dep:cortex-m", "dep:embedded-hal", "dep:embedded-hal-async"]
# Single-core variants
stm32wle4c8 = ["embassy-stm32/stm32wle4c8"]
stm32wle4cb = ["embassy-stm32/stm32wle4cb"]
stm32wle4cc = ["embassy-stm32/stm32wle4cc"]
stm32wle4j8 = ["embassy-stm32/stm32wle4j8"]
stm32wle4jb = ["embassy-stm32/stm32wle4jb"]
stm32wle4jc = ["embassy-stm32/stm32wle4jc"]
stm32wle5c8 = ["embassy-stm32/stm32wle5c8"]
stm32wle5cb = ["embassy-stm32/stm32wle5cb"]
stm32wle5cc = ["embassy-stm32/stm32wle5cc"]
stm32wle5j8 = ["embassy-stm32/stm32wle5j8"]
stm32wle5jb = ["embassy-stm32/stm32wle5jb"]
stm32wle5jc = ["embassy-stm32/stm32wle5jc"]
stm32wle4c8 = ["hal", "embassy-stm32/stm32wle4c8"]
stm32wle4cb = ["hal", "embassy-stm32/stm32wle4cb"]
stm32wle4cc = ["hal", "embassy-stm32/stm32wle4cc"]
stm32wle4j8 = ["hal", "embassy-stm32/stm32wle4j8"]
stm32wle4jb = ["hal", "embassy-stm32/stm32wle4jb"]
stm32wle4jc = ["hal", "embassy-stm32/stm32wle4jc"]
stm32wle5c8 = ["hal", "embassy-stm32/stm32wle5c8"]
stm32wle5cb = ["hal", "embassy-stm32/stm32wle5cb"]
stm32wle5cc = ["hal", "embassy-stm32/stm32wle5cc"]
stm32wle5j8 = ["hal", "embassy-stm32/stm32wle5j8"]
stm32wle5jb = ["hal", "embassy-stm32/stm32wle5jb"]
stm32wle5jc = ["hal", "embassy-stm32/stm32wle5jc"]
# Dual-core variants
stm32wl54cc-cm0p = ["embassy-stm32/stm32wl54cc-cm0p"]
stm32wl54cc-cm4 = ["embassy-stm32/stm32wl54cc-cm4"]
stm32wl54jc-cm0p = ["embassy-stm32/stm32wl54jc-cm0p"]
stm32wl54jc-cm4 = ["embassy-stm32/stm32wl54jc-cm4"]
stm32wl55cc-cm0p = ["embassy-stm32/stm32wl55cc-cm0p"]
stm32wl55cc-cm4 = ["embassy-stm32/stm32wl55cc-cm4"]
stm32wl55jc-cm0p = ["embassy-stm32/stm32wl55jc-cm0p"]
stm32wl55jc-cm4 = ["embassy-stm32/stm32wl55jc-cm4"]
stm32wl54cc-cm0p = ["hal", "embassy-stm32/stm32wl54cc-cm0p"]
stm32wl54cc-cm4 = ["hal", "embassy-stm32/stm32wl54cc-cm4"]
stm32wl54jc-cm0p = ["hal", "embassy-stm32/stm32wl54jc-cm0p"]
stm32wl54jc-cm4 = ["hal", "embassy-stm32/stm32wl54jc-cm4"]
stm32wl55cc-cm0p = ["hal", "embassy-stm32/stm32wl55cc-cm0p"]
stm32wl55cc-cm4 = ["hal", "embassy-stm32/stm32wl55cc-cm4"]
stm32wl55jc-cm0p = ["hal", "embassy-stm32/stm32wl55jc-cm0p"]
stm32wl55jc-cm4 = ["hal", "embassy-stm32/stm32wl55jc-cm4"]
[dependencies]
embassy-stm32 = { version = "0.5.0", features = ["unstable-pac"] }
embassy-time = "0.5.0"
defmt = "1.0.1"
cortex-m = { version = "0.7.6", features = ["inline-asm"] }
embedded-hal = "1.0.0"
embedded-hal-async = "1.0.0"
embassy-stm32 = { version = "0.5.0", features = ["unstable-pac"], optional = true }
embassy-time = { version = "0.5.0", optional = true }
defmt = { version = "1.0.1", optional = true }
cortex-m = { version = "0.7.6", features = ["inline-asm"], optional = true }
embedded-hal = { version = "1.0.0", optional = true }
embedded-hal-async = { version = "1.0.0", optional = true }
[profile.release]
debug = 2

13
src/lib.rs
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@@ -1,13 +1,22 @@
#![no_std]
#![cfg_attr(feature = "hal", no_std)]
#![allow(async_fn_in_trait)]
pub mod error;
pub mod modulations;
#[cfg(feature = "hal")]
pub mod error;
#[cfg(feature = "hal")]
pub mod radio;
#[cfg(feature = "hal")]
pub mod spi;
#[cfg(feature = "hal")]
pub mod traits;
#[cfg(feature = "hal")]
pub use error::RadioError;
#[cfg(feature = "hal")]
pub use radio::{PaSelection, Radio};
#[cfg(feature = "hal")]
pub use spi::SubGhzSpiDevice;
#[cfg(feature = "hal")]
pub use traits::{Configure, Receive, Transmit};

202
src/modulations/bpsk.rs
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@@ -1,16 +1,24 @@
#[cfg(feature = "hal")]
use defmt::debug;
#[cfg(feature = "hal")]
use embedded_hal::digital::OutputPin;
#[cfg(feature = "hal")]
use embedded_hal_async::spi::SpiDevice;
#[cfg(feature = "hal")]
use crate::{
RadioError,
radio::{PaSelection, PacketType, Radio, RampTime, irq},
traits::{Configure, Transmit},
};
#[cfg(not(feature = "hal"))]
use std::vec::Vec;
/// BPSK bitrate
/// Formula: register = (32 * 32_000_000) / bps
#[derive(Clone, Copy, defmt::Format)]
#[derive(Clone, Copy)]
#[cfg_attr(feature = "hal", derive(defmt::Format))]
pub enum Bitrate {
/// 100 bits per second
Bps100,
@@ -22,7 +30,7 @@ pub enum Bitrate {
impl Bitrate {
/// Get the 3-byte register value for this bitrate
fn to_bytes(self) -> [u8; 3] {
pub fn to_bytes(self) -> [u8; 3] {
let val = match self {
Bitrate::Bps100 => 0x9C4000,
Bitrate::Bps600 => 0x1A0AAA,
@@ -32,7 +40,8 @@ impl Bitrate {
}
}
#[derive(Clone, Copy, defmt::Format)]
#[derive(Clone, Copy)]
#[cfg_attr(feature = "hal", derive(defmt::Format))]
pub enum CrcType {
None,
/// Using a common 0x07 polynomial
@@ -42,7 +51,7 @@ pub enum CrcType {
}
impl CrcType {
fn compute(self, data: &[u8]) -> (u16, usize) {
pub fn compute(self, data: &[u8]) -> (u16, usize) {
match self {
CrcType::None => (0, 0),
CrcType::Crc8 => {
@@ -76,7 +85,7 @@ impl CrcType {
}
}
fn write(self, crc: u16, buf: &mut [u8]) {
pub fn write(self, crc: u16, buf: &mut [u8]) {
match self {
CrcType::None => {}
CrcType::Crc8 => {
@@ -90,14 +99,15 @@ impl CrcType {
}
}
#[derive(Clone, Copy, defmt::Format)]
#[derive(Clone, Copy)]
#[cfg_attr(feature = "hal", derive(defmt::Format))]
pub enum Whitening {
None,
Ccitt,
}
impl Whitening {
fn apply(self, seed: u16, data: &mut [u8]) {
pub fn apply(self, seed: u16, data: &mut [u8]) {
match self {
Whitening::None => return,
Whitening::Ccitt => {}
@@ -117,7 +127,20 @@ impl Whitening {
}
}
#[derive(Clone, Copy, defmt::Format)]
#[cfg(not(feature = "hal"))]
pub struct DecodeResult {
/// On which bit the sync word was found
pub bit_offset: usize,
/// Signal was phase-inverted
pub inverted: bool,
/// Decoded payload
pub payload: Vec<u8>,
/// CRC matches
pub crc_valid: bool,
}
#[derive(Clone, Copy)]
#[cfg_attr(feature = "hal", derive(defmt::Format))]
pub enum BpskPacket {
/// No framing, just send raw data
Raw,
@@ -129,8 +152,6 @@ pub enum BpskPacket {
sync_word: [u8; 32],
/// Sync word length
sync_word_len: usize,
/// Enable/disable reporting length in the packet
include_len: bool,
/// CRC size (0, 1 or 2 bytes)
crc_type: CrcType,
/// Whitening algorithm
@@ -145,42 +166,46 @@ impl BpskPacket {
Self::Framing {
preamble_len: 32,
// Baker-13 code (2 bytes)
sync_word: [0x1F, 0x35, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00],
sync_word: [
0x1F, 0x35, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
],
sync_word_len: 2,
include_len: true,
crc_type: CrcType::Crc16,
whitening: Whitening::Ccitt,
whitening_seed: 0x1FF,
}
}
fn to_bytes(self, payload: &[u8], buf: &mut [u8]) -> Result<u8, RadioError> {
#[cfg(feature = "hal")]
pub fn to_bytes(self, payload: &[u8], buf: &mut [u8]) -> Result<u8, RadioError> {
match self {
BpskPacket::Raw => {
// Simple copy operation, no modifications made
buf[..payload.len()].copy_from_slice(payload);
payload.len().try_into().map_err(|_| RadioError::PayloadTooLarge)
payload
.len()
.try_into()
.map_err(|_| RadioError::PayloadTooLarge)
}
BpskPacket::Framing {
preamble_len,
sync_word,
sync_word_len,
include_len,
crc_type,
whitening,
whitening_seed,
} => {
let len_field_size = if include_len { 1 } else { 0 };
let len_field_size = 1;
let crc_size = match crc_type {
CrcType::None => 0,
CrcType::Crc8 => 1,
CrcType::Crc16 => 2,
};
// Validate packet length
let total = preamble_len + sync_word_len + len_field_size + payload.len() + crc_size;
let total =
preamble_len + sync_word_len + len_field_size + payload.len() + crc_size;
if total > buf.len() {
return Err(RadioError::PayloadTooLarge);
@@ -200,12 +225,13 @@ impl BpskPacket {
// Actual payload starts here
let data_start = pos;
// If enabled in the config, write length info
if include_len {
let payload_len: u8 = payload.len().try_into().map_err(|_| RadioError::PayloadTooLarge)?;
buf[pos] = payload_len;
pos += 1;
}
// Write length info
let payload_len: u8 = payload
.len()
.try_into()
.map_err(|_| RadioError::PayloadTooLarge)?;
buf[pos] = payload_len;
pos += 1;
// Copy the original payload itself
buf[pos..pos + payload.len()].copy_from_slice(payload);
@@ -224,8 +250,127 @@ impl BpskPacket {
}
}
}
#[cfg(not(feature = "hal"))]
pub fn decode(&self, data: &[u8]) -> Vec<DecodeResult> {
match self {
// Can't do much with Raw packets so just return the same data and accept as valid
BpskPacket::Raw => vec![DecodeResult {
bit_offset: 0,
inverted: false,
payload: data.to_vec(),
crc_valid: true,
}],
BpskPacket::Framing {
preamble_len: _,
sync_word,
sync_word_len,
crc_type,
whitening,
whitening_seed,
} => {
let sync_word = &sync_word[..*sync_word_len];
let sync_bits = sync_word_len * 8;
let total_bits = data.len() * 8;
let mut results = Vec::new();
let crc_len = match crc_type {
CrcType::None => 0,
CrcType::Crc8 => 1,
CrcType::Crc16 => 2,
};
// Go through every bit, giving space to the sync word length
for i in 0..total_bits.saturating_sub(sync_bits) {
let mut matching: usize = 0;
for j in 0..sync_bits {
// Compare the sync word bit-by-bit against the data stream
let data_bit = (data[(i + j) / 8] >> (7 - ((i + j) % 8))) & 1;
let sync_bit = (sync_word[j / 8] >> (7 - (j % 8))) & 1;
if data_bit == sync_bit {
matching += 1;
}
}
// Allow up to 2 bit errors, if <= 2 bits match or unmatch, it's an accepted
// normal or phase-inverted data
let inverted = if sync_bits - matching <= 2 {
false
} else if matching <= 2 {
true
} else {
continue;
};
// Extract bytes that happen after the sync word is found at any bit offset
let bit_start = i + sync_bits;
let remaining_bytes = (total_bits - bit_start) / 8;
if remaining_bytes == 0 {
continue;
}
// Reassemble bytes from arbitrary bit positions after sync word is found at offset `i`
let mut raw = vec![0u8; remaining_bytes];
for b in 0..remaining_bytes {
let mut byte = 0u8;
for bit in 0..8 {
let idx = bit_start + b * 8 + bit;
let mut val = (data[idx / 8] >> (7 - (idx % 8))) & 1;
// Handle the 180 degree phase ambiguity
if inverted {
val ^= 1;
}
byte |= val << (7 - bit);
}
raw[b] = byte;
}
// De-whiten by applying the same whitening operation again (it's reversible)
whitening.apply(*whitening_seed, &mut raw);
// Extract payload length
let (payload_start, payload_len) = (1, raw[0] as usize);
if payload_len == 0 {
continue;
}
if payload_start + payload_len + crc_len > raw.len() {
continue;
}
// Verify CRC over len field and payload
let crc_data = &raw[..payload_start + payload_len];
let (crc_computed, _) = crc_type.compute(crc_data);
let crc_valid = match crc_type {
CrcType::None => true,
CrcType::Crc8 => raw[payload_start + payload_len] == crc_computed as u8,
CrcType::Crc16 => {
// Assemble u16 from two bytes
let received = ((raw[payload_start + payload_len] as u16) << 8)
| raw[payload_start + payload_len + 1] as u16;
received == crc_computed
}
};
results.push(DecodeResult {
bit_offset: i,
inverted,
payload: raw[payload_start..payload_start + payload_len].to_vec(),
crc_valid,
});
}
results
}
}
}
}
#[cfg(feature = "hal")]
#[derive(Clone, Copy, defmt::Format)]
pub struct BpskConfig {
pub frequency: u32,
@@ -236,6 +381,7 @@ pub struct BpskConfig {
pub packet: BpskPacket,
}
#[cfg(feature = "hal")]
impl Default for BpskConfig {
fn default() -> Self {
Self {
@@ -250,12 +396,14 @@ impl Default for BpskConfig {
}
/// BPSK modulation - borrows a Radio, implements Configure + Transmit
#[cfg(feature = "hal")]
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,
}
#[cfg(feature = "hal")]
impl<'a, SPI: SpiDevice, TX: OutputPin, RX: OutputPin, EN: OutputPin>
BpskRadio<'a, SPI, TX, RX, EN>
{
@@ -283,6 +431,7 @@ impl<'a, SPI: SpiDevice, TX: OutputPin, RX: OutputPin, EN: OutputPin>
}
}
#[cfg(feature = "hal")]
impl<SPI: SpiDevice, TX: OutputPin, RX: OutputPin, EN: OutputPin> Configure
for BpskRadio<'_, SPI, TX, RX, EN>
{
@@ -315,6 +464,7 @@ impl<SPI: SpiDevice, TX: OutputPin, RX: OutputPin, EN: OutputPin> Configure
}
}
#[cfg(feature = "hal")]
impl<SPI: SpiDevice, TX: OutputPin, RX: OutputPin, EN: OutputPin> Transmit
for BpskRadio<'_, SPI, TX, RX, EN>
{

3
src/modulations/mod.rs
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@@ -1,4 +1,7 @@
pub mod bpsk;
#[cfg(feature = "hal")]
pub mod fsk;
#[cfg(feature = "hal")]
pub mod lora;
#[cfg(feature = "hal")]
pub mod msk;