fixed-dsp

fixed-dsp is a Rust fixed-point DSP library focused on Q15/Q31 algorithms with behavior close to CMSIS-DSP. It also supports differential testing (difftest) against CMSIS C reference implementations.

中文

Highlights

• #![no_std] friendly for embedded targets
• Q15/Q31 implementations (i16 / i32)
• Modular structure: basic ops, matrix, statistics, complex math, transforms, MFCC
• Optional difftest feature: when enabled, compiles selected CMSIS-DSP C sources for differential validation

Implemented Modules

Basic

Located in src/basic.

• Trigonometric functions: sin_i16 / sin_i32, cos_i16 / cos_i32
• Multiply and vector ops: mul_i16 / mul_i32, dot_i16 / dot_i32
• Scale and shift: scale_i16 / scale_i32, shift_i16 / shift_i32
• Offset and log: offset_i16 / offset_i32, vlog_i16 / vlog_i32
• Sqrt and division: sqrt_i16 / sqrt_i32, div_i16 / div_i32

Matrix

Located in src/matrix.

• Matrix<T> view struct
• mat_add_i16 / mat_add_i32
• mat_mul_i16 / mat_mul_i32
• mat_vec_mul_i16 / mat_vec_mul_i32

Statistics

Located in src/statistics.

• absmax_i16 / absmax_i32

Complex

Located in src/complex.

• cmplx_mag_i16 / cmplx_mag_i32

Transform

Located in src/transform.

• Bit-reversal: bitreversal_i16 / bitreversal_i32
• CFFT: CfftI16 / CfftI32
• RFFT: RfftI16 / RfftI32
• Radix-4 butterfly: forward/inverse Q15/Q31 kernels
• MFCC: MfccI16 / MfccI32

Quick Start

1. Add dependency

For local workspace development, use a path dependency:

[dependencies]
fixed-dsp = "0.2"

2. Basic example (Q15 sine)

use fixed_dsp::basic::sin_i16;

fn main() {
	// In Q15, 0x4000 is approximately pi/2.
	let x: i16 = 0x4000;
	let y = sin_i16(x);
	println!("sin_q15 = {}", y);
}

3. CFFT example (Q15)

use fixed_dsp::transform::CfftI16;

fn main() {
	let fft = CfftI16::new(16, false, true);

	// Interleaved complex format: [re0, im0, re1, im1, ...]
	let mut data = [0i16; 32];
	data[0] = 0x4000; // simple impulse

	fft.run(&mut data);
}

Build and Test

With the difftest feature enabled, build.rs compiles referenced C files under CMSIS-DSP/Source and links them into tests.

cargo test --lib --tests --features difftest

Notes:

• Requires a working host C compiler (cc/clang)
• Requires a complete CMSIS-DSP directory
• Without difftest, integration tests that rely on CMSIS extern symbols are expected to fail at link time

Design Goals

• Provide readable and maintainable fixed-point DSP implementations in Rust
• Continuously validate numerical behavior against CMSIS-DSP through difftest
• Serve as a stable base for embedded deployment and algorithm iteration