Digital Signal Processing (DSP) in Embedded Systems

# Digital Signal Processing (DSP) in Embedded Systems

Digital Signal Processing (DSP) is an integral part of many embedded systems. DSP algorithms and techniques are often implemented in hardware such as ASICs (Application Specific Integrated Circuits) or FPGAs (Field Programmable Gate Arrays) for performance reasons.

For example, a basic DSP operation is the Finite Impulse Response (FIR) filter. Here's a simple implementation of an FIR filter in C, a language commonly used in embedded systems:

```c
void fir_filter(int *coefficients, int *input, int *output, int length) {
    for (int i = 0; i < length; i++) {
        output[i] = 0;
        for (int j = 0; j <= i; j++) {
            output[i] += coefficients[j] * input[i - j];
        }
    }
}
```

In this code, `coefficients` are the filter coefficients, `input` is the input signal, `output` is the output signal, and `length` is the number of samples in the input signal.

DSP operations can also be implemented using a DSP library such as CMSIS-DSP, a free library provided by ARM for its Cortex-M series of processors. Here's how you might implement an FIR filter using CMSIS-DSP:

```c
#include "arm_math.h"

#define NUM_TAPS 32
#define BLOCK_SIZE 32

float32_t firStateF32[BLOCK_SIZE + NUM_TAPS - 1];
arm_fir_instance_f32 S;
float32_t coefficients[NUM_TAPS] = {...};
float32_t input[BLOCK_SIZE], output[BLOCK_SIZE];

void init() {
    arm_fir_init_f32(&S, NUM_TAPS, (float32_t *)&coefficients[0], &firStateF32[0], BLOCK_SIZE);
}

void process() {
    arm_fir_f32(&S, input, output, BLOCK_SIZE);
}
```

In this code, `coefficients` are the filter coefficients, `input` is the input signal, `output` is the output signal, `NUM_TAPS` is the number of coefficients in the FIR filter, and `BLOCK_SIZE` is the number of samples processed per call to `arm_fir_f32`.

These examples show how DSP operations can be implemented in embedded systems, both directly in C and using a DSP library. These techniques are applicable to a wide range of DSP tasks beyond just FIR filtering.