mordae/pico-sdr
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Use 8 bit samples

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After adjusting for the noise floor, we can use 8 bit samples for all
supported bandwidths.
This commit is contained in:
Jan Hamal Dvořák 2024-02-23 23:20:42 +01:00
parent d3e403df33
commit 78b07b9c09
1 changed files with 9 additions and 11 deletions
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20
src/main.c
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@ -40,7 +40,7 @@
#define CLK_SYS_HZ (250 * MHZ) #define CLK_SYS_HZ (250 * MHZ)
#define BANDWIDTH 100000 #define BANDWIDTH 100000
#define IQ_BLOCK_LEN 32 #define IQ_BLOCK_LEN 64
#define XOR_ADDR 0x1000 #define XOR_ADDR 0x1000
#define LO_COS_ACCUMULATOR (&pio1->sm[2].pinctrl) #define LO_COS_ACCUMULATOR (&pio1->sm[2].pinctrl)
@ -530,11 +530,12 @@ static void rf_tx_stop()
static void rf_rx(void) static void rf_rx(void)
{ {
static int16_t block[IQ_BLOCK_LEN]; static int8_t block[IQ_BLOCK_LEN];
uint32_t prev_transfers = dma_hw->ch[dma_ch_in_cos].transfer_count; uint32_t prev_transfers = dma_hw->ch[dma_ch_in_cos].transfer_count;
unsigned pos = 0; unsigned pos = 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;
while (true) { while (true) {
if (multicore_fifo_rvalid()) { if (multicore_fifo_rvalid()) {
@ -558,7 +559,7 @@ static void rf_rx(void)
pos = (pos + IQ_BLOCK_LEN) & (RX_WORDS - 1); pos = (pos + IQ_BLOCK_LEN) & (RX_WORDS - 1);
int16_t *blockptr = block; int8_t *blockptr = block;
for (int i = 0; i < IQ_BLOCK_LEN / 2; i++) { for (int i = 0; i < IQ_BLOCK_LEN / 2; i++) {
uint32_t cos_pos = *cos_ptr++; uint32_t cos_pos = *cos_ptr++;
@ -569,11 +570,8 @@ static void rf_rx(void)
int I = cos_neg - cos_pos; int I = cos_neg - cos_pos;
int Q = sin_neg - sin_pos; int Q = sin_neg - sin_pos;
dcI = (dcI * 8191 + ((int64_t)I << 16)) / 8192; I = (I * noise_floor_inv) >> 16;
dcQ = (dcQ * 8191 + ((int64_t)Q << 16)) / 8192; Q = (Q * noise_floor_inv) >> 16;
I -= dcI >> 16;
Q -= dcQ >> 16;
*blockptr++ = I; *blockptr++ = I;
*blockptr++ = Q; *blockptr++ = Q;
@ -679,7 +677,7 @@ static void do_rx(int rx_pin, int bias_pin, float freq, char mode)
printf("Frequency: %.0f\n", actual); printf("Frequency: %.0f\n", actual);
static int16_t block[IQ_BLOCK_LEN]; static int8_t block[IQ_BLOCK_LEN];
while (queue_try_remove(&iq_queue, block)) while (queue_try_remove(&iq_queue, block))
/* Flush the queue */; /* Flush the queue */;
@ -870,7 +868,7 @@ int main()
printf("\nPuppet Online!\n"); printf("\nPuppet Online!\n");
printf("clk_sys = %10.6f MHz\n", (float)clock_get_hz(clk_sys) / MHZ); printf("clk_sys = %10.6f MHz\n", (float)clock_get_hz(clk_sys) / MHZ);
queue_init(&iq_queue, IQ_BLOCK_LEN * 2, 256); queue_init(&iq_queue, IQ_BLOCK_LEN * sizeof(int8_t), 256);
static char cmd[83]; static char cmd[83];
int cmdlen = 0; int cmdlen = 0;