Improve SNR, re-add frequency rounding
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da73da4e38
commit
f45d4c7ac2
1 changed files with 70 additions and 64 deletions
134
src/main.c
134
src/main.c
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@ -1,3 +1,4 @@
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#include <math.h>
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#include <pico/stdlib.h>
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#include <pico/stdio_usb.h>
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#include <pico/multicore.h>
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@ -21,7 +22,7 @@
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#include <stdlib.h>
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#define VREG_VOLTAGE VREG_VOLTAGE_1_20
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#define CLK_SYS_HZ (306 * MHZ)
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#define CLK_SYS_HZ (320 * MHZ)
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#define RX_PIN 10
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#define FB_PIN 11
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@ -35,7 +36,7 @@
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#define IQ_SAMPLES 32
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#define IQ_BLOCK_LEN (2 * IQ_SAMPLES)
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#define IQ_QUEUE_LEN 8
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#define IQ_QUEUE_LEN 16
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#define XOR_ADDR 0x1000
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#define LO_BITS_DEPTH 15
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@ -48,17 +49,17 @@
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static uint32_t lo_cos[LO_WORDS] __attribute__((__aligned__(1 << LO_BITS_DEPTH)));
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static uint32_t lo_sin[LO_WORDS] __attribute__((__aligned__(1 << LO_BITS_DEPTH)));
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#define DECIMATE 4
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#define INIT_SAMPLE_RATE 100000
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#define INIT_FREQ 94600000
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#define BASE_GAIN (1 << 15)
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#define ATTN_BITS 8
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static int sample_rate = INIT_SAMPLE_RATE;
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static int gain = BASE_GAIN / (CLK_SYS_HZ / INIT_SAMPLE_RATE / 2);
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static int frequency = INIT_FREQ;
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static int sample_rate = INIT_SAMPLE_RATE;
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#define BASE_GAIN (1 << 15)
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#define ATTN_BITS 10
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#define DECIMATE 4
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static int gain = BASE_GAIN / (CLK_SYS_HZ / INIT_SAMPLE_RATE);
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static queue_t iq_queue;
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static uint8_t iq_queue_buffer[IQ_QUEUE_LEN][IQ_BLOCK_LEN];
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@ -246,12 +247,11 @@ static void lo_generate_phase(uint32_t *buf, size_t len, uint32_t step, uint32_t
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}
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}
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static void rx_lo_init(uint32_t freq)
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static void rx_lo_init(double freq)
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{
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const uint32_t frac = (8 + 16llu * CLK_SYS_HZ / (8 << LO_BITS_DEPTH)) >> 4;
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uint32_t step = ((uint64_t)freq << 32) / (uint64_t)CLK_SYS_HZ;
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step /= frac;
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step *= frac;
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double frac = (double)CLK_SYS_HZ / (8 << LO_BITS_DEPTH);
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freq = roundf(freq / frac) * frac;
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uint32_t step = freq * 4294967296.0 / CLK_SYS_HZ;
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lo_generate_phase(lo_cos, LO_WORDS, step, COS_PHASE);
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lo_generate_phase(lo_sin, LO_WORDS, step, SIN_PHASE);
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}
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@ -434,7 +434,13 @@ inline static uint32_t pio_sm_get_blocking_unsafe(pio_hw_t *pio, int sm)
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return pio->rxf[sm];
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}
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inline static int nextI()
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static int Ia1, Ia2, Ia3;
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static int Ib1, Ib2, Ib3;
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static int Qa1, Qa2, Qa3;
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static int Qb1, Qb2, Qb3;
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inline static void accI()
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{
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static uint16_t py, px;
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@ -448,25 +454,14 @@ inline static int nextI()
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py = y;
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px = x;
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int s = ((int)ny << 1) + (int)nx;
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int s0 = s;
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uint32_t s = (ny << 1) + nx;
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static int a1, a2;
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s = s0 - a2;
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a2 = a1;
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a1 = s0;
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s0 = s;
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static int b1, b2;
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s = s0 - b2;
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b2 = b1;
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b1 = s0;
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s0 = s;
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return s >> 2;
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Ia1 += s;
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Ia2 += Ia1;
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Ia3 += Ia2;
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}
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inline static int nextQ()
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inline static void accQ()
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{
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static uint16_t py, px;
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@ -480,22 +475,43 @@ inline static int nextQ()
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py = y;
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px = x;
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int s = ((int)ny << 1) + (int)nx;
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int s0 = s;
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uint32_t s = (ny << 1) + nx;
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static int a1, a2;
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s = s0 - a2;
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a2 = a1;
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a1 = s0;
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s0 = s;
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Qa1 += s;
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Qa2 += Qa1;
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Qa3 += Qa2;
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}
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static int b1, b2;
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s = s0 - b2;
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b2 = b1;
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b1 = s0;
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s0 = s;
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inline static int getI()
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{
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uint32_t c1, c2, c3;
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return s >> 2;
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c3 = Ia3 - Ib3;
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Ib3 = Ia3;
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c2 = c3 - Ib2;
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Ib2 = c3;
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c1 = c2 - Ib1;
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Ib1 = c2;
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return (int)c1;
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}
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inline static int getQ()
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{
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uint32_t c1, c2, c3;
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c3 = Qa3 - Qb3;
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Qb3 = Qa3;
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c2 = c3 - Qb2;
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Qb2 = c3;
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c1 = c2 - Qb1;
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Qb1 = c2;
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return (int)c1;
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}
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static void rf_rx(void)
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@ -511,28 +527,18 @@ static void rf_rx(void)
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uint8_t *blockptr = block;
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for (int i = 0; i < IQ_SAMPLES; i++) {
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int I = 0, Q = 0;
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for (int d = 0; d < DECIMATE; d++) {
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accI();
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accQ();
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}
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Q += nextQ();
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I += nextI();
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int I = getI() * gain;
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int Q = getQ() * gain;
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I -= nextQ();
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Q += nextI();
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Q -= nextQ();
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I -= nextI();
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I += nextQ();
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Q -= nextI();
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I *= gain;
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I >>= ATTN_BITS;
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*blockptr++ = I + 128;
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Q *= gain;
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Q >>= ATTN_BITS;
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*blockptr++ = Q + 128;
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}
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@ -550,13 +556,13 @@ static void run_command(uint8_t cmd, uint32_t arg)
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if (0x01 == cmd) {
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/* Tune to a new center frequency */
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frequency = arg;
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rx_lo_init(frequency + sample_rate);
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rx_lo_init(frequency);
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} else if (0x02 == cmd) {
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/* Set the rate at which IQ sample pairs are sent */
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sample_rate = arg;
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gain = BASE_GAIN / (CLK_SYS_HZ / sample_rate / 2);
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gain = BASE_GAIN / (CLK_SYS_HZ / sample_rate);
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dma_timer_set_fraction(dma_t_samp, 1, CLK_SYS_HZ / (sample_rate * DECIMATE));
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rx_lo_init(frequency + sample_rate);
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rx_lo_init(frequency);
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}
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}
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@ -647,7 +653,7 @@ int main()
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queue_init(&iq_queue, sizeof(uint8_t *), IQ_QUEUE_LEN);
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rx_lo_init(frequency + sample_rate);
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rx_lo_init(frequency);
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/* We need to have the sampling timer ready. */
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dma_t_samp = dma_claim_unused_timer(true);
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