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Improve the FIR filter a bit

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This commit is contained in:
Jan Hamal Dvořák 2024-07-23 20:16:40 +02:00
parent 884d84bbf9
commit 63ca3c6439
1 changed files with 30 additions and 12 deletions
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42
src/main.c
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@ -384,34 +384,52 @@ static void rf_rx_stop(void)
inline static int next_sample(const uint32_t *buf, int *h) inline static int next_sample(const uint32_t *buf, int *h)
{ {
int x1 = buf[0] - buf[1]; int x3 = 2 * (buf[0] - buf[1]);
int x2 = 0; int x2 = 0;
int x3 = buf[5] - buf[4]; int x1 = 2 * (buf[5] - buf[4]);
int x4 = 0; int x0 = 0;
int sample = 18 * h[9] + 14 * h[8] - 32 * h[7] - 33 * h[6] + 106 * h[5] + 362 * h[4] + const int c[] = { 4, 2, -8, -9, 19, 55 };
565 * h[3] + 565 * h[2] + 362 * h[1] + 106 * h[0] - 33 * x1 - 32 * x2 +
14 * x3 + 18 * x4;
int sample = 0;
sample += (c[0]) * h[10];
sample += (c[0] + c[1]) * h[9];
sample += (c[0] + c[1] + c[2]) * h[8];
sample += (c[0] + c[1] + c[2] + c[3]) * h[7];
sample += (c[1] + c[2] + c[3] + c[4]) * h[6];
sample += (c[2] + c[3] + c[4] + c[5]) * h[5];
sample += (c[3] + c[4] + c[5] + c[5]) * h[4];
sample += (c[4] + c[5] + c[5] + c[4]) * h[3];
sample += (c[5] + c[5] + c[4] + c[3]) * h[2];
sample += (c[5] + c[4] + c[3] + c[2]) * h[1];
sample += (c[4] + c[3] + c[2] + c[1]) * h[0];
sample += (c[3] + c[2] + c[1] + c[0]) * x3;
sample += (c[2] + c[1] + c[0]) * x2;
sample += (c[1] + c[0]) * x1;
sample += (c[0]) * x0;
sample *= gain;
sample /= 256;
h[10] = h[6];
h[9] = h[5]; h[9] = h[5];
h[8] = h[4]; h[8] = h[4];
h[7] = h[3]; h[7] = h[3];
h[6] = h[2]; h[6] = h[2];
h[5] = h[1]; h[5] = h[1];
h[4] = h[0]; h[4] = h[0];
h[3] = x1; h[3] = x3;
h[2] = x2; h[2] = x2;
h[1] = x3; h[1] = x1;
h[0] = x4; h[0] = x0;
return gain * sample / 565; return sample;
} }
static void rf_rx(void) static void rf_rx(void)
{ {
const uint32_t base = (uint32_t)rx_cos; const uint32_t base = (uint32_t)rx_cos;
int prevI[10] = { 0 }; int prevI[11] = { 0 };
int prevQ[10] = { 0 }; int prevQ[11] = { 0 };
int pos = 0; int pos = 0;
while (true) { while (true) {