Getting Started with STM32 DSP Library

As an embedded development engineer, sometimes we need to perform complex mathematical operations on microcontrollers. Don’t worry, the STM32 DSP library is designed to solve this problem! This article will quickly guide you through getting started with the STM32 DSP library to easily perform efficient mathematical calculations.

What is the DSP Library?

DSP stands for Digital Signal Processing. The STM32 DSP library is a set of optimized mathematical functions that allows us to efficiently perform various mathematical operations on microcontrollers with ARM Cortex-M cores.

Imagine that the DSP library is like equipping your STM32 with a scientific calculator, capable of easily handling various complex calculations!

How to Use the DSP Library in Your Project

To use the DSP library, we need to complete the following steps:

1. 1. Copy the relevant files from the CMSIS directory into the project
2. 2. Add the relevant paths and keywords in Keil
3. 3. Include the header files
4. 4. Link the DSP library files

The specific operations are as follows:

1. 1. Create a DSPlib folder in the project directory and copy the files from the CMSIS\DSP\Include directory into it
2. 2. Also copy the arm_cortexM3l_math.lib file from the CMSIS\DSP\Lib\ARM directory into the DSPlib folder
3. 3. In Keil’s Options for Target, under the C/C++ tab, add the Include path: ..\DSPlib\Include
4. 4. Add the keyword in Define:

    ARM_MATH_CM3

5. 5. Include the header file in main.c:

    #include "arm_math.h"

6. 6. In the Linker tab, add the lib file:

    ..\DSPlib\arm_cortexM3l_math.lib

Note: For different Cortex-M cores, you need to select the corresponding lib file, such as arm_cortexM4l_math.lib for the M4 core.

Common Functions in the DSP Library

The DSP library provides a large number of mathematical functions, here are a few commonly used ones:

1. 1. Basic Mathematical Functions

Upload failed, network error.

Retry

• • arm_abs_f32: Calculate absolute value

1. 2. Fast Mathematical Functions

• • arm_add_f32: Addition
• • arm_mult_f32: Multiplication
• • arm_sqrt_f32: Square root

• arm_sin_f32: Sine

1. 3. Filtering Functions

• • arm_cos_f32: Cosine
• • arm_atan2_f32: Arctangent

• arm_fir_f32: FIR filtering

1. 4. Matrix Operations

• • arm_iir_lattice_f32: IIR filtering

• arm_mat_add_f32: Matrix addition

• • arm_mat_mult_f32: Matrix multiplication
• • arm_mat_inverse_f32: Matrix inversion

Practical Application Example

Suppose we want to implement a simple FIR low-pass filter, the code example is as follows:

#include "arm_math.h"
#define BLOCK_SIZE 32
#define NUM_TAPS 29

static float32_t firStateF32[BLOCK_SIZE + NUM_TAPS - 1];
static float32_t firCoeffs32[NUM_TAPS] = {/* Filter coefficients */};

arm_fir_instance_f32 S;

float32_t inputF32[BLOCK_SIZE];
float32_t outputF32[BLOCK_SIZE];

int main()
{
    uint32_t blockSize = BLOCK_SIZE;
    uint32_t numBlocks = 1;
    
    arm_fir_init_f32(&S, NUM_TAPS, (float32_t *)&firCoeffs32[0], &firStateF32[0], blockSize);

    /* Assign values to inputF32 here */

    for(int i=0; i < numBlocks; i++)
    {
        arm_fir_f32(&S, &inputF32[0], &outputF32[0], blockSize);
    }

    /* outputF32 is the filtered result */

    while(1);
}

Notes:

• • Before using DSP library functions, initialize the relevant structures
• • Input and output data should use float32_t type
• • Ensure correct array size settings to avoid memory overflow

Common Issues and Solutions

1. 1. Compilation error finding arm_math.h solution: Check if the Include path is set correctly
2. 2. Linker error indicating missing __aeabi_f2d and other symbols solution: Ensure the correct lib files are added
3. 3. Incorrect runtime results solution: Check if the input data types are correct, avoid mixing float and double

Practical Suggestions

Mastering the DSP library requires practice. You can start with simple mathematical operations, such as calculating averages and standard deviations, gradually transitioning to filter design, FFT, and other complex applications. Use an oscilloscope to observe the signal changes before and after processing to deepen your understanding.

Remember, while the DSP library is powerful, it also has its limitations. For some simple operations, implementing them directly in C may be more efficient. Flexibly choose based on actual needs, which is the wise choice.‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌‌