有没有FIR滤波器的C语言实现

有的，下面是一个简单的FIR滤波器的C语言实现：

#define MAX_LENGTH 1000

double FIR_filter(double input, double *coefficients, int length, double *history)
{
    double output = 0;

    // shift the history buffer
    for (int i = length - 1; i > 0; i--)
    {
        history[i] = history[i - 1];
    }

    // add the new input to the history buffer
    history[0] = input;

    // calculate the output using the filter coefficients and history buffer
    for (int i = 0; i < length; i++)
    {
        output += coefficients[i] * history[i];
    }

    return output;
}

int main()
{
    double coefficients[] = {0.1, 0.2, 0.3, 0.2, 0.1}; // filter coefficients
    double history[MAX_LENGTH] = {0}; // history buffer
    double input = 0; // input signal
    double output = 0; // filtered output

    // loop over input signal and filter the data
    for (int i = 0; i < MAX_LENGTH; i++)
    {
        // get input signal (e.g. from ADC)
        // ...

        // apply the filter
        output = FIR_filter(input, coefficients, 5, history);

        // do something with the filtered output (e.g. send to DAC)
        // ...
    }

    return 0;
}

在上面的代码中，`FIR_filter`函数接受一个输入信号、一组滤波器系数、滤波器长度和历史缓冲区作为参数，并返回滤波后的输出信号。在主函数中，我们可以循环读取输入信号，并将其传递给滤波器函数进行滤波。滤波后的输出信号可以用于其他用途，例如传输到DAC。