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Fix DC offset removal, simplify...

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This commit is contained in:
Jan Hamal Dvořák 2025-08-30 20:33:37 +02:00
parent 5f264e023d
commit 4b9f377bb0
Signed by: mordae
GPG key ID: 1782BCC23EE007B9
1 changed files with 76 additions and 127 deletions
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203
src/main.c
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@ -21,43 +21,43 @@
#include <limits.h> #include <limits.h>
#include <stdlib.h> #include <stdlib.h>
#define VREG_VOLTAGE VREG_VOLTAGE_1_20 #define VREG_VOLTAGE VREG_VOLTAGE_1_30
#define CLK_SYS_HZ (320 * MHZ) #define CLK_SYS_HZ (300 * MHZ)
#define RX_PIN 10 #define RX_PIN 10
#define FB_PIN 6 #define FB_PIN 6
#define PSU_PIN 23 #define PSU_PIN 23
#define PIO pio0 #define PIO pio0
#define SM_RX 0 #define SM_RX 0
#define SM_BIAS 1 #define SM_BIAS 1
#define SM_COS 2 #define SM_COS 2
#define SM_SIN 3 #define SM_SIN 3
#define IQ_SAMPLES 32 #define IQ_SAMPLES 32
#define IQ_BLOCK_LEN (2 * IQ_SAMPLES) #define IQ_BLOCK_LEN (2 * IQ_SAMPLES)
#define IQ_QUEUE_LEN 16 #define IQ_QUEUE_LEN 16
#define XOR_ADDR 0x1000 #define XOR_ADDR 0x1000
#define LO_BITS_DEPTH 15 #define LO_BITS_DEPTH 15
#define LO_WORDS (1 << (LO_BITS_DEPTH - 2)) #define LO_WORDS (1 << (LO_BITS_DEPTH - 2))
#define LO_COS_ACCUMULATOR (&PIO->sm[SM_COS].pinctrl) #define LO_COS_ACCUMULATOR (&PIO->sm[SM_COS].pinctrl)
#define LO_SIN_ACCUMULATOR (&PIO->sm[SM_SIN].pinctrl) #define LO_SIN_ACCUMULATOR (&PIO->sm[SM_SIN].pinctrl)
#define SIN_PHASE (0u) #define SIN_PHASE (0u)
#define COS_PHASE (3u << 30) #define COS_PHASE (3u << 30)
static uint32_t lo_cos[LO_WORDS] __attribute__((__aligned__(1 << LO_BITS_DEPTH))); static uint32_t lo_cos[LO_WORDS] __attribute__((__aligned__(1 << LO_BITS_DEPTH)));
static uint32_t lo_sin[LO_WORDS] __attribute__((__aligned__(1 << LO_BITS_DEPTH))); static uint32_t lo_sin[LO_WORDS] __attribute__((__aligned__(1 << LO_BITS_DEPTH)));
#define INIT_SAMPLE_RATE 100000 #define INIT_SAMPLE_RATE 100000
#define INIT_FREQ 94600000 #define INIT_FREQ 94600000
static int frequency = INIT_FREQ; static int frequency = INIT_FREQ;
static int sample_rate = INIT_SAMPLE_RATE; static int sample_rate = INIT_SAMPLE_RATE;
#define BASE_GAIN (1 << 15) #define ATTN_BITS 16
#define ATTN_BITS 12 #define BASE_GAIN (1 << 23)
#define DECIMATE 4 #define DC_OFFSET (int)(127.4 * (1 << ATTN_BITS))
static int gain = BASE_GAIN / (CLK_SYS_HZ / INIT_SAMPLE_RATE); static int gain = BASE_GAIN / (CLK_SYS_HZ / INIT_SAMPLE_RATE);
@ -108,7 +108,7 @@ static void init_rx()
pio_gpio_init(PIO, RX_PIN); pio_gpio_init(PIO, RX_PIN);
const uint16_t insn[] = { const uint16_t insn[] = {
pio_encode_in(pio_pins, 1) | pio_encode_delay(0), pio_encode_in(pio_pins, 1),
}; };
pio_program_t prog = { pio_program_t prog = {
@ -143,16 +143,8 @@ static void init_bias()
gpio_set_slew_rate(FB_PIN, GPIO_SLEW_RATE_SLOW); gpio_set_slew_rate(FB_PIN, GPIO_SLEW_RATE_SLOW);
const uint16_t insn[] = { const uint16_t insn[] = {
pio_encode_mov(pio_isr, pio_null), pio_encode_mov_not(pio_pins, pio_pins) | pio_encode_sideset(1, 1) |
pio_encode_in(pio_y, 4), pio_encode_delay(0),
pio_encode_in(pio_pins, 1) | pio_encode_delay(15),
pio_encode_in(pio_pins, 1) | pio_encode_delay(15),
pio_encode_mov(pio_y, pio_isr),
pio_encode_mov(pio_x, pio_isr),
pio_encode_jmp_x_dec(6),
pio_encode_mov_not(pio_pins, pio_pins) | pio_encode_sideset(1, 1),
}; };
pio_program_t prog = { pio_program_t prog = {
@ -286,7 +278,7 @@ static void rf_rx_start()
channel_config_set_write_increment(&dma_conf, false); channel_config_set_write_increment(&dma_conf, false);
channel_config_set_chain_to(&dma_conf, dma_ch_cos); channel_config_set_chain_to(&dma_conf, dma_ch_cos);
dma_channel_configure(dma_ch_cp, &dma_conf, LO_SIN_ACCUMULATOR, LO_COS_ACCUMULATOR, 1, dma_channel_configure(dma_ch_cp, &dma_conf, LO_SIN_ACCUMULATOR, LO_COS_ACCUMULATOR, 1,
false); false);
/* Read lo_cos into accumulator I with XOR. */ /* Read lo_cos into accumulator I with XOR. */
dma_conf = dma_channel_get_default_config(dma_ch_cos); dma_conf = dma_channel_get_default_config(dma_ch_cos);
@ -296,7 +288,7 @@ static void rf_rx_start()
channel_config_set_ring(&dma_conf, false, LO_BITS_DEPTH); channel_config_set_ring(&dma_conf, false, LO_BITS_DEPTH);
channel_config_set_chain_to(&dma_conf, dma_ch_sin); channel_config_set_chain_to(&dma_conf, dma_ch_sin);
dma_channel_configure(dma_ch_cos, &dma_conf, LO_COS_ACCUMULATOR + XOR_ADDR / 4, lo_cos, 1, dma_channel_configure(dma_ch_cos, &dma_conf, LO_COS_ACCUMULATOR + XOR_ADDR / 4, lo_cos, 1,
false); false);
/* Read lo_sin into accumulator Q with XOR. */ /* Read lo_sin into accumulator Q with XOR. */
dma_conf = dma_channel_get_default_config(dma_ch_sin); dma_conf = dma_channel_get_default_config(dma_ch_sin);
@ -306,7 +298,7 @@ static void rf_rx_start()
channel_config_set_ring(&dma_conf, false, LO_BITS_DEPTH); channel_config_set_ring(&dma_conf, false, LO_BITS_DEPTH);
channel_config_set_chain_to(&dma_conf, dma_ch_pio_cos); channel_config_set_chain_to(&dma_conf, dma_ch_pio_cos);
dma_channel_configure(dma_ch_sin, &dma_conf, LO_SIN_ACCUMULATOR + XOR_ADDR / 4, lo_sin, 1, dma_channel_configure(dma_ch_sin, &dma_conf, LO_SIN_ACCUMULATOR + XOR_ADDR / 4, lo_sin, 1,
false); false);
/* Copy mixed I accumulator to PIO adder I. */ /* Copy mixed I accumulator to PIO adder I. */
dma_conf = dma_channel_get_default_config(dma_ch_pio_cos); dma_conf = dma_channel_get_default_config(dma_ch_pio_cos);
@ -316,7 +308,7 @@ static void rf_rx_start()
channel_config_set_dreq(&dma_conf, pio_get_dreq(PIO, SM_COS, true)); channel_config_set_dreq(&dma_conf, pio_get_dreq(PIO, SM_COS, true));
channel_config_set_chain_to(&dma_conf, dma_ch_pio_sin); channel_config_set_chain_to(&dma_conf, dma_ch_pio_sin);
dma_channel_configure(dma_ch_pio_cos, &dma_conf, &PIO->txf[SM_COS], LO_COS_ACCUMULATOR, 1, dma_channel_configure(dma_ch_pio_cos, &dma_conf, &PIO->txf[SM_COS], LO_COS_ACCUMULATOR, 1,
false); false);
/* Copy mixed Q accumulator to PIO adder Q. */ /* Copy mixed Q accumulator to PIO adder Q. */
dma_conf = dma_channel_get_default_config(dma_ch_pio_sin); dma_conf = dma_channel_get_default_config(dma_ch_pio_sin);
@ -326,7 +318,7 @@ static void rf_rx_start()
channel_config_set_dreq(&dma_conf, pio_get_dreq(PIO, SM_SIN, true)); channel_config_set_dreq(&dma_conf, pio_get_dreq(PIO, SM_SIN, true));
channel_config_set_chain_to(&dma_conf, dma_ch_rx); channel_config_set_chain_to(&dma_conf, dma_ch_rx);
dma_channel_configure(dma_ch_pio_sin, &dma_conf, &PIO->txf[SM_SIN], LO_SIN_ACCUMULATOR, 1, dma_channel_configure(dma_ch_pio_sin, &dma_conf, &PIO->txf[SM_SIN], LO_SIN_ACCUMULATOR, 1,
false); false);
/* Trigger I accumulator values push. */ /* Trigger I accumulator values push. */
dma_conf = dma_channel_get_default_config(dma_ch_samp_cos); dma_conf = dma_channel_get_default_config(dma_ch_samp_cos);
@ -337,7 +329,7 @@ static void rf_rx_start()
channel_config_set_high_priority(&dma_conf, true); channel_config_set_high_priority(&dma_conf, true);
channel_config_set_chain_to(&dma_conf, dma_ch_samp_sin); channel_config_set_chain_to(&dma_conf, dma_ch_samp_sin);
dma_channel_configure(dma_ch_samp_cos, &dma_conf, &PIO->sm[SM_COS].instr, &samp_insn, 1, dma_channel_configure(dma_ch_samp_cos, &dma_conf, &PIO->sm[SM_COS].instr, &samp_insn, 1,
false); false);
/* Trigger Q accumulator values push. */ /* Trigger Q accumulator values push. */
dma_conf = dma_channel_get_default_config(dma_ch_samp_sin); dma_conf = dma_channel_get_default_config(dma_ch_samp_sin);
@ -347,7 +339,7 @@ static void rf_rx_start()
channel_config_set_high_priority(&dma_conf, true); channel_config_set_high_priority(&dma_conf, true);
channel_config_set_chain_to(&dma_conf, dma_ch_samp_cos); channel_config_set_chain_to(&dma_conf, dma_ch_samp_cos);
dma_channel_configure(dma_ch_samp_sin, &dma_conf, &PIO->sm[SM_SIN].instr, &samp_insn, 1, dma_channel_configure(dma_ch_samp_sin, &dma_conf, &PIO->sm[SM_SIN].instr, &samp_insn, 1,
false); false);
init_bias(); init_bias();
init_adder(); init_adder();
@ -426,92 +418,50 @@ inline static void led_set(bool on)
gpio_put(PICO_DEFAULT_LED_PIN, on); gpio_put(PICO_DEFAULT_LED_PIN, on);
} }
inline static uint32_t pio_sm_get_blocking_unsafe(pio_hw_t *pio, int sm)
{
while (pio->fstat & (1u << (PIO_FSTAT_RXEMPTY_LSB + sm)))
asm volatile("nop");
return pio->rxf[sm];
}
static int Ia1, Ia2, Ia3;
static int Ib1, Ib2, Ib3;
static int Qa1, Qa2, Qa3;
static int Qb1, Qb2, Qb3;
inline static void accI()
{
static uint16_t py, px;
uint32_t yx = pio_sm_get_blocking_unsafe(PIO, SM_COS);
uint16_t y = yx >> 16;
uint16_t x = yx;
uint16_t ny = py - y;
uint16_t nx = px - x;
py = y;
px = x;
uint32_t s = (ny << 1) + nx;
Ia1 += s;
Ia2 += Ia1;
Ia3 += Ia2;
}
inline static void accQ()
{
static uint16_t py, px;
uint32_t yx = pio_sm_get_blocking_unsafe(PIO, SM_SIN);
uint16_t y = yx >> 16;
uint16_t x = yx;
uint16_t ny = py - y;
uint16_t nx = px - x;
py = y;
px = x;
uint32_t s = (ny << 1) + nx;
Qa1 += s;
Qa2 += Qa1;
Qa3 += Qa2;
}
inline static int getI() inline static int getI()
{ {
uint32_t c1, c2, c3; static uint16_t py, px;
c3 = Ia3 - Ib3; uint32_t yx = pio_sm_get_blocking(PIO, SM_COS);
Ib3 = Ia3; uint16_t y = yx >> 16;
uint16_t x = yx;
c2 = c3 - Ib2; uint16_t ny = py - y;
Ib2 = c3; uint16_t nx = px - x;
c1 = c2 - Ib1; py = y;
Ib1 = c2; px = x;
return (int)c1; int s = ((ny << 1) + nx) * gain;
static int dc;
dc += (s - dc) >> ATTN_BITS;
s -= dc;
return (s + DC_OFFSET) >> ATTN_BITS;
} }
inline static int getQ() inline static int getQ()
{ {
uint32_t c1, c2, c3; static uint16_t py, px;
c3 = Qa3 - Qb3; uint32_t yx = pio_sm_get_blocking(PIO, SM_SIN);
Qb3 = Qa3; uint16_t y = yx >> 16;
uint16_t x = yx;
c2 = c3 - Qb2; uint16_t ny = py - y;
Qb2 = c3; uint16_t nx = px - x;
c1 = c2 - Qb1; py = y;
Qb1 = c2; px = x;
return (int)c1; int s = ((ny << 1) + nx) * gain;
static int dc;
dc += (s - dc) >> ATTN_BITS;
s -= dc;
return (s + DC_OFFSET) >> ATTN_BITS;
} }
static void rf_rx(void) static void rf_rx(void)
@ -527,19 +477,21 @@ static void rf_rx(void)
uint8_t *blockptr = block; uint8_t *blockptr = block;
for (int i = 0; i < IQ_SAMPLES; i++) { for (int i = 0; i < IQ_SAMPLES; i++) {
for (int d = 0; d < DECIMATE; d++) { int I = getI();
accI(); int Q = getQ();
accQ();
}
int I = getI() * gain; if (I < 0)
int Q = getQ() * gain; I = 0;
else if (I > 255)
I = 255;
I >>= ATTN_BITS; if (Q < 0)
*blockptr++ = I + 128; Q = 0;
else if (Q > 255)
Q = 255;
Q >>= ATTN_BITS; *blockptr++ = I;
*blockptr++ = Q + 128; *blockptr++ = Q;
} }
if (queue_try_add(&iq_queue, &block)) { if (queue_try_add(&iq_queue, &block)) {
@ -561,7 +513,7 @@ static void run_command(uint8_t cmd, uint32_t arg)
/* Set the rate at which IQ sample pairs are sent */ /* Set the rate at which IQ sample pairs are sent */
sample_rate = arg; sample_rate = arg;
gain = BASE_GAIN / (CLK_SYS_HZ / sample_rate); gain = BASE_GAIN / (CLK_SYS_HZ / sample_rate);
dma_timer_set_fraction(dma_t_samp, 1, CLK_SYS_HZ / (sample_rate * DECIMATE)); dma_timer_set_fraction(dma_t_samp, 1, CLK_SYS_HZ / sample_rate);
rx_lo_init(frequency); rx_lo_init(frequency);
} }
} }
@ -613,10 +565,7 @@ static void do_rx()
fwrite(block, IQ_BLOCK_LEN, 1, stdout); fwrite(block, IQ_BLOCK_LEN, 1, stdout);
fflush(stdout); fflush(stdout);
} else { } else {
int wait = xorshift() >> (32 - 15); sleep_us(1);
for (int i = 0; i < wait; i++)
asm volatile("nop");
} }
} }
@ -634,7 +583,7 @@ int main()
vreg_set_voltage(VREG_VOLTAGE); vreg_set_voltage(VREG_VOLTAGE);
set_sys_clock_khz(CLK_SYS_HZ / KHZ, true); set_sys_clock_khz(CLK_SYS_HZ / KHZ, true);
clock_configure(clk_peri, 0, CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS, CLK_SYS_HZ, clock_configure(clk_peri, 0, CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLKSRC_PLL_SYS, CLK_SYS_HZ,
CLK_SYS_HZ); CLK_SYS_HZ);
/* Enable PSU PWM mode. */ /* Enable PSU PWM mode. */
gpio_init(PSU_PIN); gpio_init(PSU_PIN);
@ -657,13 +606,13 @@ int main()
/* We need to have the sampling timer ready. */ /* We need to have the sampling timer ready. */
dma_t_samp = dma_claim_unused_timer(true); dma_t_samp = dma_claim_unused_timer(true);
dma_timer_set_fraction(dma_t_samp, 1, CLK_SYS_HZ / (sample_rate * DECIMATE)); dma_timer_set_fraction(dma_t_samp, 1, CLK_SYS_HZ / sample_rate);
while (true) { while (true) {
if (check_command() > 0) { if (check_command() > 0) {
static const uint32_t header[3] = { __builtin_bswap32(0x52544c30), static const uint32_t header[3] = { __builtin_bswap32(0x52544c30),
__builtin_bswap32(5), __builtin_bswap32(5),
__builtin_bswap32(29) }; __builtin_bswap32(29) };
fwrite(header, sizeof header, 1, stdout); fwrite(header, sizeof header, 1, stdout);
fflush(stdout); fflush(stdout);