mordae/pico-sdr
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Tweak LO dithering for better performance

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This commit is contained in:
Jan Hamal Dvořák 2024-07-10 10:21:04 +02:00
parent 2fc01539f0
commit 57e36203aa
1 changed files with 8 additions and 8 deletions

16
src/main.c
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@ -251,12 +251,11 @@ static void lo_generate(uint32_t *buf, double freq, uint32_t phase)
{ {
freq_step = STEP_BASE * freq; freq_step = STEP_BASE * freq;
unsigned down = 4 + __builtin_clz(freq_step); unsigned down = 2 + __builtin_clz(freq_step);
for (size_t i = 0; i < LO_WORDS; i++) { for (size_t i = 0; i < LO_WORDS; i++) {
uint32_t bits = 0; uint32_t bits = 0;
int shift = (rnd_next() >> down) - (rnd_next() >> down) + (rnd_next() >> down) - int shift = (rnd_next() >> down) - (rnd_next() >> down);
(rnd_next() >> down);
for (int j = 0; j < 32; j++) { for (int j = 0; j < 32; j++) {
bits |= (phase + shift) >> 31; bits |= (phase + shift) >> 31;
@ -272,13 +271,12 @@ static void lo_tweak(uint32_t *buf, uint32_t phase)
{ {
static size_t i = 0; static size_t i = 0;
uint32_t bits = 0; uint32_t bits = 0;
unsigned down = 4 + __builtin_clz(freq_step); unsigned down = 2 + __builtin_clz(freq_step);
phase += freq_step * i * 32; phase += freq_step * i * 32;
for (int j = 0; j < 32; j++) { for (int j = 0; j < 32; j++) {
int shift = (rnd_next() >> down) - (rnd_next() >> down) + (rnd_next() >> down) - int shift = (rnd_next() >> down) - (rnd_next() >> down);
(rnd_next() >> down);
bits |= (phase + shift) >> 31; bits |= (phase + shift) >> 31;
bits <<= 1; bits <<= 1;
phase += freq_step; phase += freq_step;
@ -602,8 +600,10 @@ static void rf_rx(void)
iq_queue_pos = (iq_queue_pos + 1) & (IQ_QUEUE_LEN - 1); iq_queue_pos = (iq_queue_pos + 1) & (IQ_QUEUE_LEN - 1);
} }
lo_tweak(lo_cos, COS_PHASE); for (int i = 0; i < 8; i++) {
lo_tweak(lo_sin, SIN_PHASE); lo_tweak(lo_cos, COS_PHASE);
lo_tweak(lo_sin, SIN_PHASE);
}
} }
} }