mordae/pico-sdr
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Introduce averaging before decimation

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Jan Hamal Dvořák 2024-02-24 20:22:47 +01:00
parent 50b1947723
commit 813a23e699
1 changed files with 64 additions and 24 deletions
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88
src/main.c
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@ -38,9 +38,12 @@
#include <stdlib.h>
#define CLK_SYS_HZ (250 * MHZ)
#define BANDWIDTH 100000
#define BANDWIDTH 768000
#define DECIMATION 32
#define LPF_SIZE DECIMATION
#define IQ_BLOCK_LEN 64
#define RX_BLOCK_LEN (IQ_BLOCK_LEN * DECIMATION)
#define XOR_ADDR 0x1000
#define LO_COS_ACCUMULATOR (&pio1->sm[2].pinctrl)
@ -51,11 +54,13 @@
static uint32_t lo_cos[LO_WORDS] __attribute__((__aligned__(LO_WORDS * 4)));
static uint32_t lo_sin[LO_WORDS] __attribute__((__aligned__(LO_WORDS * 4)));
#define RX_BITS_DEPTH 10
#define RX_BITS_DEPTH 12
#define RX_WORDS (1 << RX_BITS_DEPTH)
static uint32_t rx_cos[RX_WORDS] __attribute__((__aligned__(RX_WORDS * 4)));
static uint32_t rx_sin[RX_WORDS] __attribute__((__aligned__(RX_WORDS * 4)));
static_assert(RX_WORDS > RX_BLOCK_LEN, "RX buffers too short for given decimation");
/* rx -> cp -> cos -> sin -> pio_cos -> pio_sin -> rx ... */
static int dma_ch_rx = -1;
static int dma_ch_cp = -1;
@ -529,10 +534,20 @@ static void rf_rx(void)
uint32_t prev_transfers = dma_hw->ch[dma_ch_in_cos].transfer_count;
unsigned pos = 0;
static int lpIh1[LPF_SIZE];
static int lpQh1[LPF_SIZE];
int lpIa1 = 0;
int lpQa1 = 0;
static int lpIh2[LPF_SIZE];
static int lpQh2[LPF_SIZE];
int lpIa2 = 0;
int lpQa2 = 0;
int64_t dcI = 0, dcQ = 0;
int noise_floor = sqrt((float)CLK_SYS_HZ / (float)BANDWIDTH * 3.0 / 4.0);
int noise_floor_inv = (1 << 16) / noise_floor;
int noise_floor = sqrt((float)CLK_SYS_HZ / BANDWIDTH * DECIMATION * 3.0 / 4.0);
int64_t noise_floor_inv = (1ll << 32) / noise_floor;
while (true) {
if (multicore_fifo_rvalid()) {
@ -542,45 +557,70 @@ static void rf_rx(void)
}
int delta = prev_transfers - dma_hw->ch[dma_ch_in_cos].transfer_count;
gap = IQ_BLOCK_LEN - delta;
gap = RX_BLOCK_LEN - delta;
while (delta < IQ_BLOCK_LEN) {
while (delta < RX_BLOCK_LEN) {
delta = prev_transfers - dma_hw->ch[dma_ch_in_cos].transfer_count;
sleep_us(100);
}
prev_transfers -= IQ_BLOCK_LEN;
prev_transfers -= RX_BLOCK_LEN;
uint32_t *cos_ptr = rx_cos + pos;
uint32_t *sin_ptr = rx_sin + pos;
pos = (pos + IQ_BLOCK_LEN) & (RX_WORDS - 1);
pos = (pos + RX_BLOCK_LEN) & (RX_WORDS - 1);
int8_t *blockptr = block;
for (int i = 0; i < IQ_BLOCK_LEN / 2; i++) {
uint32_t cos_pos = *cos_ptr++;
uint32_t cos_neg = *cos_ptr++;
uint32_t sin_pos = *sin_ptr++;
uint32_t sin_neg = *sin_ptr++;
int64_t dI = 0;
int64_t dQ = 0;
int I = cos_neg - cos_pos;
int Q = sin_neg - sin_pos;
for (int d = 0; d < DECIMATION; d++) {
uint32_t cos_pos = *cos_ptr++;
uint32_t cos_neg = *cos_ptr++;
uint32_t sin_pos = *sin_ptr++;
uint32_t sin_neg = *sin_ptr++;
int64_t I64 = (int64_t)I << 32;
int64_t Q64 = (int64_t)Q << 32;
int I = cos_neg - cos_pos;
int Q = sin_neg - sin_pos;
I = (I64 - dcI) >> 32;
Q = (Q64 - dcQ) >> 32;
int lpP = d & (LPF_SIZE - 1);
dcI = ((dcI << 20) - dcI + I64) >> 20;
dcQ = ((dcQ << 20) - dcQ + Q64) >> 20;
lpIa1 += I - lpIh1[lpP];
lpQa1 += Q - lpQh1[lpP];
I = (I * noise_floor_inv) >> 16;
Q = (Q * noise_floor_inv) >> 16;
lpIh1[lpP] = I;
lpQh1[lpP] = Q;
*blockptr++ = I;
*blockptr++ = Q;
I = lpIa1 / LPF_SIZE;
Q = lpQa1 / LPF_SIZE;
lpIa2 += I - lpIh2[lpP];
lpQa2 += Q - lpQh2[lpP];
lpIh2[lpP] = I;
lpQh2[lpP] = Q;
I = lpIa2 / LPF_SIZE;
Q = lpQa2 / LPF_SIZE;
int64_t I64 = (int64_t)I << 32;
int64_t Q64 = (int64_t)Q << 32;
dI += (I64 - dcI) >> 32;
dQ += (Q64 - dcQ) >> 32;
dcI = ((dcI << 20) - dcI + I64) >> 20;
dcQ = ((dcQ << 20) - dcQ + Q64) >> 20;
}
dI = (dI * noise_floor_inv) >> 32;
dQ = (dQ * noise_floor_inv) >> 32;
*blockptr++ = dI;
*blockptr++ = dQ;
}
if (!queue_try_add(&iq_queue, block)) {