mordae/pico-sdr
1
2
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

Improve LO signal generation

Browse source 
Signed-off-by: Jan Hamal Dvořák <mordae@anilinux.org>
This commit is contained in:
Jan Hamal Dvořák 2024-01-25 21:45:45 +01:00
parent 64417f3ab7
commit 0ae392dc51
1 changed files with 34 additions and 15 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

49
src/main.c
View file

@ -34,7 +34,7 @@
#include <limits.h>
#include <stdlib.h>
#define CLK_SYS_HZ (250 * MHZ)
#define CLK_SYS_HZ (264 * MHZ)
#define EXTRA_BITS 4
#define NUM_SAMPLES 32
@ -260,25 +260,44 @@ static float lo_freq_init(float req_freq)
const float step_hz = (float)CLK_SYS_HZ / (LO_WORDS * 32);
float freq = roundf(req_freq / step_hz) * step_hz;
unsigned step = UINT_MAX / (float)CLK_SYS_HZ * freq;
unsigned acos = UINT_MAX / 4;
unsigned asin = 0, bsin = 0;
unsigned step = (float)UINT_MAX / (float)CLK_SYS_HZ * freq;
unsigned sin_acc = 0;
unsigned cos_acc = UINT_MAX / 4;
unsigned sin_err = 0;
unsigned cos_err = 0;
int prev_sin_bit = 0;
int prev_cos_bit = 1;
for (int i = 0; i < LO_WORDS; i++) {
unsigned bcos = 0;
unsigned bsin = 0, bcos = 0;
for (int j = 0; j < 32; j++) {
bcos |= acos >> 31;
bcos <<= 1;
acos += step;
bsin |= asin >> 31;
int sin_bit = (sin_acc + sin_err) >> 31;
bsin |= sin_bit;
bsin <<= 1;
asin += step;
int cos_bit = (cos_acc + cos_err) >> 31;
bcos |= cos_bit;
bcos <<= 1;
if (prev_sin_bit != sin_bit) {
sin_err = (sin_acc + sin_err) & 0x7fffffff;
}
if (prev_cos_bit != cos_bit) {
cos_err = (cos_acc + cos_err) & 0x7fffffff;
}
prev_sin_bit = sin_bit;
prev_cos_bit = cos_bit;
sin_acc += step;
cos_acc += step;
}
lo_cos[i] = bcos;
lo_sin[i] = bsin;
lo_cos[i] = bcos;
}
return freq;
@ -748,7 +767,7 @@ static void command(const char *cmd)
if (3 == sscanf(cmd, " rx %i %f %[\a]", &n, &f, tmp)) {
watch_init(n);
float actual = lo_freq_init(f);
printf("actual frequency = %f\n", actual);
printf("actual frequency = %10.6f Hz\n", actual / MHZ);
dma_channel_config dma_conf = dma_channel_get_default_config(rx_dma);
channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_32);
@ -811,7 +830,7 @@ static void command(const char *cmd)
send_init(n);
float actual = lo_freq_init(f);
printf("actual frequency = %f\n", actual);
printf("actual frequency = %10.6f MHz\n", actual / MHZ);
dma_channel_config dma_conf = dma_channel_get_default_config(tx_dma);
channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_32);
@ -847,7 +866,7 @@ int main()
rx_dma = dma_claim_unused_channel(true);
printf("\nPuppet Online!\n");
printf("clk_sys = %10.6f MHz\n", (float)clock_get_hz(clk_sys) / 1000000.0);
printf("clk_sys = %10.6f MHz\n", (float)clock_get_hz(clk_sys) / MHZ);
#if SPEED < 3
printf("Generating mixer lookup table...\n");