mordae/pico-sdr
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Reduce jitter and use HPF to improve SNR

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This commit is contained in:
Jan Hamal Dvořák 2024-07-16 18:56:30 +02:00
parent 38b7ec34f6
commit c23f578c65
1 changed files with 26 additions and 14 deletions
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src/main.c
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@ -48,7 +48,7 @@ static uint32_t lo_cos[LO_WORDS] __attribute__((__aligned__(1 << LO_BITS_DEPTH))
#define RX_BITS_DEPTH 13
#define RX_WORDS (1 << (RX_BITS_DEPTH - 2))
static_assert(RX_STRIDE * 4 < RX_WORDS, "RX_STRIDE * 4 < RX_WORDS");
static_assert(RX_STRIDE * 4 <= RX_WORDS, "RX_STRIDE * 4 <= RX_WORDS");
static uint32_t rx_cos[RX_WORDS] __attribute__((__aligned__(1 << RX_BITS_DEPTH)));
@ -142,7 +142,7 @@ static void init_fb()
const uint16_t insn[] = {
pio_encode_mov_not(pio_pins, pio_pins) | pio_encode_sideset(1, 1) |
pio_encode_delay(0),
pio_encode_nop() | pio_encode_sideset(1, 0),
pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(0),
};
pio_program_t prog = {
@ -219,9 +219,9 @@ static void init_ad()
*/
pio_encode_in(pio_y, 32),
pio_encode_in(pio_x, 32),
pio_encode_set(pio_x, 0),
pio_encode_set(pio_y, 0),
pio_encode_jmp(1),
pio_encode_set(pio_x, 0),
pio_encode_out(pio_pc, 2),
};
pio_program_t prog = {
@ -421,6 +421,7 @@ static void rf_rx_stop(void)
static void rf_rx(void)
{
const uint32_t base = (uint32_t)rx_cos;
int prev = 0;
int pos = 0;
while (true) {
@ -463,20 +464,31 @@ static void rf_rx(void)
for (int i = 0; i < IQ_SAMPLES; i++) {
int sI = 0, sQ = 0;
int pos, neg;
/* Convert to I/Q signal. */
// +I
pos = *cos_ptr++;
neg = *cos_ptr++;
sI += pos - neg - prev;
prev = pos - neg;
sI += *cos_ptr++;
sI -= *cos_ptr++;
// +Q
pos = *cos_ptr++;
neg = *cos_ptr++;
sQ += pos - neg - prev;
prev = pos - neg;
sQ += *cos_ptr++;
sQ -= *cos_ptr++;
// -I
pos = *cos_ptr++;
neg = *cos_ptr++;
sI -= pos - neg - prev;
prev = pos - neg;
sI -= *cos_ptr++;
sI += *cos_ptr++;
sQ -= *cos_ptr++;
sQ += *cos_ptr++;
// -Q
pos = *cos_ptr++;
neg = *cos_ptr++;
sQ -= pos - neg - prev;
prev = pos - neg;
int64_t I = sI;
int64_t Q = sQ;