Fix frequency rounding

- Use less DMAs
- Improve bit counting
- Fix sample_rate changes and other fixes

grc/PicoSDR-WBFM.grc

@@ -37,7 +37,7 @@ blocks:
   id: variable
   parameters:
     comment: ''
-    value: '88_200_000'
+    value: '94_600_000'
   states:
     bus_sink: false
     bus_source: false
@@ -374,7 +374,7 @@ blocks:
     freq7: 100e6
     freq8: 100e6
     freq9: 100e6
-    gain0: '30'
+    gain0: '0'
     gain1: '10'
     gain10: '10'
     gain11: '10'

grc/PicoSDR.grc

@@ -401,7 +401,7 @@ blocks:
     freq7: 100e6
     freq8: 100e6
     freq9: 100e6
-    gain0: '30'
+    gain0: '0'
     gain1: '10'
     gain10: '10'
     gain11: '10'

src/main.c

@@ -22,43 +22,67 @@
 #include <stdlib.h>
 
 #define VREG_VOLTAGE VREG_VOLTAGE_1_20
-#define CLK_SYS_HZ (300 * MHZ)
+#define CLK_SYS_HZ (306 * MHZ)
+
+#define RX_PIN 10
+#define FB_PIN 11
 #define PSU_PIN 23
 
+#define PIO pio0
+#define SM_RX 0
+#define SM_BIAS 1
+#define SM_COS 2
+#define SM_SIN 3
+
 #define IQ_SAMPLES 32
 #define IQ_BLOCK_LEN (2 * IQ_SAMPLES)
-#define IQ_QUEUE_LEN 4
+#define IQ_QUEUE_LEN 8
 
 #define XOR_ADDR 0x1000
-#define LO_COS_ACCUMULATOR (&pio1->sm[2].pinctrl)
-#define LO_SIN_ACCUMULATOR (&pio1->sm[3].pinctrl)
-
 #define LO_BITS_DEPTH 15
 #define LO_WORDS (1 << (LO_BITS_DEPTH - 2))
+#define LO_COS_ACCUMULATOR (&PIO->sm[SM_COS].pinctrl)
+#define LO_SIN_ACCUMULATOR (&PIO->sm[SM_SIN].pinctrl)
+#define SIN_PHASE (0u)
+#define COS_PHASE (3u << 30)
+
 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)));
 
 #define DECIMATE 4
-#define RX_STRIDE (2 * IQ_SAMPLES * DECIMATE)
-#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 uint32_t rx_cos[RX_WORDS] __attribute__((__aligned__(1 << RX_BITS_DEPTH)));
-static uint32_t rx_sin[RX_WORDS] __attribute__((__aligned__(1 << RX_BITS_DEPTH)));
 
 #define INIT_SAMPLE_RATE 100000
 #define INIT_FREQ 94600000
+#define INIT_GAIN 127
 
 #define NUM_GAINS 29
 static int gains[NUM_GAINS] = { 0,   9,	  14,  27,  37,	 77,  87,  125, 144, 157,
 				166, 197, 207, 229, 254, 280, 297, 328, 338, 364,
 				372, 386, 402, 421, 434, 439, 445, 480, 496 };
 static int sample_rate = INIT_SAMPLE_RATE;
+static int max_amplitude = CLK_SYS_HZ / INIT_SAMPLE_RATE / 2;
+static int gain = INIT_GAIN;
+static int frequency = INIT_FREQ;
 
-#define SIN_PHASE (0u)
+static queue_t iq_queue;
-#define COS_PHASE (3u << 30)
+static uint8_t iq_queue_buffer[IQ_QUEUE_LEN][IQ_BLOCK_LEN];
+static size_t iq_queue_pos = 0;
+
+static uint32_t rnd = 0;
+
+inline static __unused uint32_t rnd_next()
+{
+	rnd = rnd * 0x41c64e6d + 12345;
+	return rnd;
+}
+
+static void dma_channel_clear_chain_to(int ch)
+{
+	uint32_t ctrl = dma_hw->ch[ch].al1_ctrl;
+	ctrl &= ~DMA_CH0_CTRL_TRIG_CHAIN_TO_BITS;
+	ctrl |= ch << DMA_CH0_CTRL_TRIG_CHAIN_TO_LSB;
+	dma_hw->ch[ch].al1_ctrl = ctrl;
+}
 
 /* rx -> cp -> cos -> sin -> pio_cos -> pio_sin -> rx ... */
 static int dma_ch_rx = -1;
@@ -68,235 +92,182 @@ static int dma_ch_sin = -1;
 static int dma_ch_pio_cos = -1;
 static int dma_ch_pio_sin = -1;
 
-static int dma_ch_samp_trig = -1;
 static int dma_ch_samp_cos = -1;
 static int dma_ch_samp_sin = -1;
 
 static int dma_t_samp = -1;
 
-static int dma_ch_in_cos = -1;
+static int origin_rx = -1;
-static int dma_ch_in_sin = -1;
+static int origin_bias = -1;
+static int origin_adder = 0;
 
-static queue_t iq_queue;
+static void init_rx()
-static uint8_t iq_queue_buffer[IQ_QUEUE_LEN][IQ_BLOCK_LEN];
-static size_t iq_queue_pos = 0;
-
-static uint32_t rnd = 0;
-
-inline static uint32_t rnd_next()
 {
-	rnd = rnd * 0x41c64e6d + 12345;
+	gpio_disable_pulls(RX_PIN);
-	return rnd;
+	pio_gpio_init(PIO, RX_PIN);
-}
-
-static void bias_set_gain(int gain)
-{
-	if (gain > 9)
-		gain = 9;
-	else if (gain < 0)
-		gain = 0;
-
-	pio1->sm[0].execctrl = (pio1->sm[0].execctrl & ~PIO_SM0_EXECCTRL_WRAP_BOTTOM_BITS) |
-			       ((19 - gain) << PIO_SM0_EXECCTRL_WRAP_BOTTOM_LSB);
-}
-
-static void bias_init(int in_pin, int out_pin)
-{
-	gpio_disable_pulls(in_pin);
-	gpio_disable_pulls(out_pin);
-
-	pio_gpio_init(pio1, out_pin);
-
-	gpio_set_input_hysteresis_enabled(in_pin, false);
-	gpio_set_drive_strength(out_pin, GPIO_DRIVE_STRENGTH_2MA);
-	gpio_set_slew_rate(out_pin, GPIO_SLEW_RATE_SLOW);
 
 	const uint16_t insn[] = {
-		pio_encode_in(pio_pins, 1),
+		pio_encode_in(pio_pins, 1) | pio_encode_delay(0),
-		pio_encode_in(pio_pins, 1),
+	};
-		pio_encode_in(pio_pins, 1),
-		pio_encode_in(pio_pins, 1),
-		pio_encode_in(pio_pins, 1),
-		pio_encode_in(pio_pins, 1),
-		pio_encode_in(pio_pins, 1),
-		pio_encode_in(pio_pins, 1),
-		pio_encode_in(pio_pins, 1),
 
-		pio_encode_mov(pio_x, pio_isr),
+	pio_program_t prog = {
+		.instructions = insn,
+		.length = sizeof(insn) / sizeof(*insn),
+		.origin = origin_rx,
+	};
+
+	if (pio_can_add_program(PIO, &prog))
+		origin_rx = pio_add_program(PIO, &prog);
+
+	pio_sm_config pc = pio_get_default_sm_config();
+	sm_config_set_in_pins(&pc, RX_PIN);
+	sm_config_set_wrap(&pc, origin_rx, origin_rx + prog.length - 1);
+	sm_config_set_clkdiv_int_frac(&pc, 1, 0);
+	sm_config_set_fifo_join(&pc, PIO_FIFO_JOIN_RX);
+	sm_config_set_in_shift(&pc, false, true, 32);
+	pio_sm_init(PIO, SM_RX, origin_rx, &pc);
+
+	pio_sm_set_consecutive_pindirs(PIO, SM_RX, RX_PIN, 1, GPIO_IN);
+}
+
+static void init_bias()
+{
+	gpio_disable_pulls(RX_PIN);
+	gpio_disable_pulls(FB_PIN);
+
+	pio_gpio_init(PIO, FB_PIN);
+
+	gpio_set_input_hysteresis_enabled(RX_PIN, false);
+	gpio_set_drive_strength(FB_PIN, GPIO_DRIVE_STRENGTH_2MA);
+	gpio_set_slew_rate(FB_PIN, GPIO_SLEW_RATE_SLOW);
+
+	PIO->input_sync_bypass = 1u << RX_PIN;
+
+	const uint16_t insn[] = {
 		pio_encode_mov(pio_isr, pio_null),
+		pio_encode_in(pio_y, 4),
+		pio_encode_in(pio_pins, 1) | pio_encode_delay(15),
+		pio_encode_in(pio_pins, 1) | pio_encode_delay(15),
 
-		pio_encode_jmp_x_dec(11),
+		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 = {
 		.instructions = insn,
 		.length = sizeof(insn) / sizeof(*insn),
-		.origin = 10,
+		.origin = origin_bias,
 	};
 
-	pio_sm_set_enabled(pio1, 0, false);
+	if (pio_can_add_program(PIO, &prog))
-	pio_sm_restart(pio1, 0);
+		origin_bias = pio_add_program(PIO, &prog);
-	pio_sm_clear_fifos(pio1, 0);
-
-	if (pio_can_add_program(pio1, &prog))
-		pio_add_program(pio1, &prog);
 
 	pio_sm_config pc = pio_get_default_sm_config();
 	sm_config_set_in_shift(&pc, false, false, 32);
 	sm_config_set_sideset(&pc, 1, false, true);
-	sm_config_set_sideset_pins(&pc, out_pin);
+	sm_config_set_sideset_pins(&pc, FB_PIN);
-	sm_config_set_in_pins(&pc, in_pin);
+	sm_config_set_in_pins(&pc, RX_PIN);
-	sm_config_set_out_pins(&pc, out_pin, 1);
+	sm_config_set_out_pins(&pc, FB_PIN, 1);
-	sm_config_set_set_pins(&pc, out_pin, 1);
+	sm_config_set_set_pins(&pc, RX_PIN, 1);
 
-	sm_config_set_wrap(&pc, prog.origin, prog.origin + prog.length - 1);
+	sm_config_set_wrap(&pc, origin_bias, origin_bias + prog.length - 1);
 
 	sm_config_set_clkdiv_int_frac(&pc, 1, 0);
-	pio_sm_init(pio1, 0, prog.origin, &pc);
+	pio_sm_init(PIO, SM_BIAS, origin_bias, &pc);
 
-	pio_sm_set_consecutive_pindirs(pio1, 0, out_pin, 1, GPIO_OUT);
+	pio_sm_exec_wait_blocking(PIO, SM_BIAS, pio_encode_set(pio_y, 31));
-
+	pio_sm_set_consecutive_pindirs(PIO, SM_BIAS, FB_PIN, 1, GPIO_OUT);
-	pio_sm_set_enabled(pio1, 0, true);
 }
 
-static void watch_init(int in_pin)
+static const uint32_t samp_insn = 16;
+
+static void init_adder()
 {
 	const uint16_t insn[] = {
-		pio_encode_in(pio_pins, 1),
+		pio_encode_out(pio_pc, 4), // 0000 +0
-	};
+		pio_encode_jmp_x_dec(0),   // 0001 +1
+		pio_encode_jmp_x_dec(0),   // 0010 +1
+		pio_encode_jmp_y_dec(0),   // 0011 +2
+		pio_encode_jmp_x_dec(0),   // 0100 +1
+		pio_encode_jmp_y_dec(0),   // 0101 +2
+		pio_encode_jmp_y_dec(0),   // 0110 +2
+		pio_encode_jmp_y_dec(1),   // 0111 +2 +1
+		pio_encode_jmp_x_dec(0),   // 1000 +1
+		pio_encode_jmp_y_dec(0),   // 1001 +2
+		pio_encode_jmp_y_dec(0),   // 1010 +2
+		pio_encode_jmp_y_dec(1),   // 1011 +2 +1
+		pio_encode_jmp_y_dec(0),   // 1100 +2
+		pio_encode_jmp_y_dec(1),   // 1101 +2 +1
+		pio_encode_jmp_y_dec(1),   // 1110 +2 +1
+		pio_encode_jmp_y_dec(3),   // 1111 +2 +2
 
-	pio_program_t prog = {
+		/*
-		.instructions = insn,
+		 * Should wrap here.
-		.length = 1,
+		 * Jump to this portion must be inserted from the outside.
-		.origin = 6,
+		 */
-	};
+		pio_encode_in(pio_y, 32),
-
+		pio_encode_in(pio_x, 32),
-	pio_sm_set_enabled(pio1, 1, false);
+		pio_encode_set(pio_y, 0),
-	pio_sm_restart(pio1, 1);
+		pio_encode_set(pio_x, 0),
-	pio_sm_clear_fifos(pio1, 1);
+		//pio_encode_jmp_y_dec(21),
-
+		//pio_encode_jmp_x_dec(22),
-	if (pio_can_add_program(pio1, &prog))
+		pio_encode_out(pio_pc, 4),
-		pio_add_program(pio1, &prog);
-
-	pio_sm_config pc = pio_get_default_sm_config();
-	sm_config_set_in_pins(&pc, in_pin);
-	sm_config_set_wrap(&pc, prog.origin, prog.origin + prog.length - 1);
-	sm_config_set_clkdiv_int_frac(&pc, 1, 0);
-	sm_config_set_fifo_join(&pc, PIO_FIFO_JOIN_RX);
-	sm_config_set_in_shift(&pc, false, true, 32);
-	pio_sm_init(pio1, 1, prog.origin, &pc);
-
-	pio_sm_set_enabled(pio1, 1, true);
-}
-
-static void adder_init()
-{
-	const uint16_t insn[] = {
-		pio_encode_jmp_y_dec(1),
-		pio_encode_out(pio_pc, 2),
-		pio_encode_out(pio_pc, 2),
-		pio_encode_jmp_x_dec(2),
-
-		/* Avoid Y-- on wrap. */
-		pio_encode_out(pio_pc, 2),
 	};
 
 	pio_program_t prog = {
 		.instructions = insn,
 		.length = sizeof(insn) / sizeof(*insn),
-		.origin = 0,
+		.origin = origin_adder,
 	};
 
-	pio_sm_set_enabled(pio1, 2, false);
+	if (pio_can_add_program(PIO, &prog))
-	pio_sm_set_enabled(pio1, 3, false);
+		origin_adder = pio_add_program(PIO, &prog);
-
-	pio_sm_restart(pio1, 2);
-	pio_sm_restart(pio1, 3);
-
-	pio_sm_clear_fifos(pio1, 2);
-	pio_sm_clear_fifos(pio1, 3);
-
-	if (pio_can_add_program(pio1, &prog))
-		pio_add_program(pio1, &prog);
 
 	pio_sm_config pc = pio_get_default_sm_config();
-	sm_config_set_wrap(&pc, prog.origin, prog.origin + prog.length - 1);
+	sm_config_set_wrap(&pc, origin_adder, origin_adder + 15);
 	sm_config_set_clkdiv_int_frac(&pc, 1, 0);
 	sm_config_set_in_shift(&pc, false, true, 32);
 	sm_config_set_out_shift(&pc, false, true, 32);
-	pio_sm_init(pio1, 2, prog.origin + prog.length - 1, &pc);
-	pio_sm_init(pio1, 3, prog.origin + prog.length - 1, &pc);
 
-	pio_sm_set_enabled(pio1, 2, true);
+	pio_sm_init(PIO, SM_COS, origin_adder, &pc);
-	pio_sm_set_enabled(pio1, 3, true);
+	pio_sm_init(PIO, SM_SIN, origin_adder, &pc);
 }
 
 #define STEP_BASE ((UINT_MAX + 1.0) / CLK_SYS_HZ)
-static uint32_t freq_step = 1;
 
-static void lo_generate(uint32_t *buf, double freq, uint32_t phase)
+static void lo_generate_phase(uint32_t *buf, size_t len, uint32_t step, uint32_t phase)
 {
-	freq_step = STEP_BASE * freq;
+	for (size_t i = 0; i < len; i++) {
-
-	unsigned down = 2 + __builtin_clz(freq_step);
-
-	for (size_t i = 0; i < LO_WORDS; i++) {
 		uint32_t bits = 0;
-		int shift = (rnd_next() >> down) - (rnd_next() >> down);
 
 		for (int j = 0; j < 32; j++) {
-			bits |= (phase + shift) >> 31;
+			bits |= phase >> 31;
 			bits <<= 1;
-			phase += freq_step;
+			phase += step;
 		}
 
 		buf[i] = bits;
 	}
 }
 
-static void lo_tweak(uint32_t *buf, uint32_t phase)
-{
-	static size_t i = 0;
-	uint32_t bits = 0;
-	unsigned down = 2 + __builtin_clz(freq_step);
-
-	phase += freq_step * i * 32;
-
-	for (int j = 0; j < 32; j++) {
-		int shift = (rnd_next() >> down) - (rnd_next() >> down);
-		bits |= (phase + shift) >> 31;
-		bits <<= 1;
-		phase += freq_step;
-	}
-
-	buf[i] = bits;
-	i = (i + 1) & (LO_WORDS - 1);
-}
-
 static void rx_lo_init(double req_freq, bool align)
 {
-	const double step_hz = (double)CLK_SYS_HZ / (8 << LO_BITS_DEPTH);
+	const double step_hz = (double)CLK_SYS_HZ / ((8 << LO_BITS_DEPTH) / 2.0);
 	double freq = req_freq;
 
 	if (align)
 		freq = round(freq / step_hz) * step_hz;
 
-	lo_generate(lo_cos, freq, COS_PHASE);
+	uint32_t step = STEP_BASE * freq;
-	lo_generate(lo_sin, freq, SIN_PHASE);
+
+	lo_generate_phase(lo_cos, LO_WORDS, step, COS_PHASE);
+	lo_generate_phase(lo_sin, LO_WORDS, step, SIN_PHASE);
 }
 
-static const uint32_t samp_insn[4] __attribute__((__aligned__(16)));
+static void rf_rx_start()
-static const uint32_t samp_insn[4] = {
-	0x4040, /* IN Y, 32 */
-	0x4020, /* IN X, 32 */
-	0xe040, /* SET Y, 0 */
-	0xe020, /* SET X, 0 */
-};
-
-static uint32_t null, one = 1;
-
-static void rf_rx_start(int rx_pin, int bias_pin)
 {
 	dma_ch_rx = dma_claim_unused_channel(true);
 	dma_ch_cp = dma_claim_unused_channel(true);
@@ -307,9 +278,6 @@ static void rf_rx_start(int rx_pin, int bias_pin)
 
 	dma_ch_samp_cos = dma_claim_unused_channel(true);
 	dma_ch_samp_sin = dma_claim_unused_channel(true);
-	dma_ch_samp_trig = dma_claim_unused_channel(true);
-
-	dma_t_samp = dma_claim_unused_timer(true);
 
 	dma_channel_config dma_conf;
 
@@ -318,9 +286,9 @@ static void rf_rx_start(int rx_pin, int bias_pin)
 	channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_32);
 	channel_config_set_read_increment(&dma_conf, false);
 	channel_config_set_write_increment(&dma_conf, false);
-	channel_config_set_dreq(&dma_conf, pio_get_dreq(pio1, 1, false));
+	channel_config_set_dreq(&dma_conf, pio_get_dreq(PIO, SM_RX, false));
 	channel_config_set_chain_to(&dma_conf, dma_ch_cp);
-	dma_channel_configure(dma_ch_rx, &dma_conf, LO_COS_ACCUMULATOR, &pio1->rxf[1], 1, false);
+	dma_channel_configure(dma_ch_rx, &dma_conf, LO_COS_ACCUMULATOR, &PIO->rxf[SM_RX], 1, false);
 
 	/* Copy accumulator I to accumulator Q. */
 	dma_conf = dma_channel_get_default_config(dma_ch_cp);
@@ -356,9 +324,9 @@ static void rf_rx_start(int rx_pin, int bias_pin)
 	channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_32);
 	channel_config_set_read_increment(&dma_conf, false);
 	channel_config_set_write_increment(&dma_conf, false);
-	channel_config_set_dreq(&dma_conf, pio_get_dreq(pio1, 2, 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);
-	dma_channel_configure(dma_ch_pio_cos, &dma_conf, &pio1->txf[2], LO_COS_ACCUMULATOR, 1,
+	dma_channel_configure(dma_ch_pio_cos, &dma_conf, &PIO->txf[SM_COS], LO_COS_ACCUMULATOR, 1,
 			      false);
 
 	/* Copy mixed Q accumulator to PIO adder Q. */
@@ -366,71 +334,67 @@ static void rf_rx_start(int rx_pin, int bias_pin)
 	channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_32);
 	channel_config_set_read_increment(&dma_conf, false);
 	channel_config_set_write_increment(&dma_conf, false);
-	channel_config_set_dreq(&dma_conf, pio_get_dreq(pio1, 3, true));
+	channel_config_set_dreq(&dma_conf, pio_get_dreq(PIO, SM_SIN, true));
 	channel_config_set_chain_to(&dma_conf, dma_ch_rx);
-	dma_channel_configure(dma_ch_pio_sin, &dma_conf, &pio1->txf[3], LO_SIN_ACCUMULATOR, 1,
+	dma_channel_configure(dma_ch_pio_sin, &dma_conf, &PIO->txf[SM_SIN], LO_SIN_ACCUMULATOR, 1,
 			      false);
 
-	/* Pacing timer for the sampling script trigger channel. */
+	/* Trigger I accumulator values push. */
-	dma_timer_set_fraction(dma_t_samp, 1, CLK_SYS_HZ / (sample_rate * DECIMATE));
+	dma_conf = dma_channel_get_default_config(dma_ch_samp_cos);
-
-	/* Sampling trigger channel. */
-	dma_conf = dma_channel_get_default_config(dma_ch_samp_trig);
 	channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_32);
 	channel_config_set_read_increment(&dma_conf, false);
 	channel_config_set_write_increment(&dma_conf, false);
 	channel_config_set_dreq(&dma_conf, dma_get_timer_dreq(dma_t_samp));
 	channel_config_set_high_priority(&dma_conf, true);
-	channel_config_set_chain_to(&dma_conf, dma_ch_samp_cos);
-	dma_channel_configure(dma_ch_samp_trig, &dma_conf, &null, &one, 1, false);
-
-	/* Trigger I accumulator values push. */
-	dma_conf = dma_channel_get_default_config(dma_ch_samp_cos);
-	channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_32);
-	channel_config_set_read_increment(&dma_conf, true);
-	channel_config_set_write_increment(&dma_conf, false);
-	channel_config_set_ring(&dma_conf, false, 4);
-	channel_config_set_high_priority(&dma_conf, true);
 	channel_config_set_chain_to(&dma_conf, dma_ch_samp_sin);
-	dma_channel_configure(dma_ch_samp_cos, &dma_conf, &pio1->sm[2].instr, samp_insn, 4, false);
+	dma_channel_configure(dma_ch_samp_cos, &dma_conf, &PIO->sm[SM_COS].instr, &samp_insn, 1,
+			      false);
 
 	/* Trigger Q accumulator values push. */
 	dma_conf = dma_channel_get_default_config(dma_ch_samp_sin);
 	channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_32);
-	channel_config_set_read_increment(&dma_conf, true);
+	channel_config_set_read_increment(&dma_conf, false);
 	channel_config_set_write_increment(&dma_conf, false);
-	channel_config_set_ring(&dma_conf, false, 4);
 	channel_config_set_high_priority(&dma_conf, true);
-	channel_config_set_chain_to(&dma_conf, dma_ch_samp_trig);
+	channel_config_set_chain_to(&dma_conf, dma_ch_samp_cos);
-	dma_channel_configure(dma_ch_samp_sin, &dma_conf, &pio1->sm[3].instr, samp_insn, 4, false);
+	dma_channel_configure(dma_ch_samp_sin, &dma_conf, &PIO->sm[SM_SIN].instr, &samp_insn, 1,
+			      false);
 
-	bias_init(rx_pin, bias_pin);
+	init_bias();
-	adder_init();
+	init_adder();
+	init_rx();
 
 	dma_channel_start(dma_ch_rx);
-	dma_channel_start(dma_ch_samp_trig);
+	dma_channel_start(dma_ch_samp_cos);
-	watch_init(rx_pin);
+
+	pio_set_sm_mask_enabled(PIO, 0x0f, true);
 }
 
 static void rf_rx_stop(void)
 {
-	pio_sm_set_enabled(pio1, 0, false);
+	pio_set_sm_mask_enabled(PIO, 0x0f, false);
-	pio_sm_set_enabled(pio1, 1, false);
-	pio_sm_set_enabled(pio1, 2, false);
-	pio_sm_set_enabled(pio1, 3, false);
 
-	pio_sm_restart(pio1, 0);
+	pio_sm_restart(PIO, 0);
-	pio_sm_restart(pio1, 1);
+	pio_sm_restart(PIO, 1);
-	pio_sm_restart(pio1, 2);
+	pio_sm_restart(PIO, 2);
-	pio_sm_restart(pio1, 3);
+	pio_sm_restart(PIO, 3);
 
-	pio_sm_clear_fifos(pio1, 0);
+	pio_sm_clear_fifos(PIO, 0);
-	pio_sm_clear_fifos(pio1, 1);
+	pio_sm_clear_fifos(PIO, 1);
-	pio_sm_clear_fifos(pio1, 2);
+	pio_sm_clear_fifos(PIO, 2);
-	pio_sm_clear_fifos(pio1, 3);
+	pio_sm_clear_fifos(PIO, 3);
 
 	sleep_us(10);
 
+	dma_channel_clear_chain_to(dma_ch_rx);
+	dma_channel_clear_chain_to(dma_ch_cp);
+	dma_channel_clear_chain_to(dma_ch_cos);
+	dma_channel_clear_chain_to(dma_ch_sin);
+	dma_channel_clear_chain_to(dma_ch_pio_cos);
+	dma_channel_clear_chain_to(dma_ch_pio_sin);
+	dma_channel_clear_chain_to(dma_ch_samp_cos);
+	dma_channel_clear_chain_to(dma_ch_samp_sin);
+
 	dma_channel_abort(dma_ch_rx);
 	dma_channel_abort(dma_ch_cp);
 	dma_channel_abort(dma_ch_cos);
@@ -439,7 +403,6 @@ static void rf_rx_stop(void)
 	dma_channel_abort(dma_ch_pio_sin);
 	dma_channel_abort(dma_ch_samp_cos);
 	dma_channel_abort(dma_ch_samp_sin);
-	dma_channel_abort(dma_ch_samp_trig);
 
 	dma_channel_cleanup(dma_ch_rx);
 	dma_channel_cleanup(dma_ch_cp);
@@ -449,7 +412,6 @@ static void rf_rx_stop(void)
 	dma_channel_cleanup(dma_ch_pio_sin);
 	dma_channel_cleanup(dma_ch_samp_cos);
 	dma_channel_cleanup(dma_ch_samp_sin);
-	dma_channel_cleanup(dma_ch_samp_trig);
 
 	dma_channel_unclaim(dma_ch_rx);
 	dma_channel_unclaim(dma_ch_cp);
@@ -459,9 +421,6 @@ static void rf_rx_stop(void)
 	dma_channel_unclaim(dma_ch_pio_sin);
 	dma_channel_unclaim(dma_ch_samp_cos);
 	dma_channel_unclaim(dma_ch_samp_sin);
-	dma_channel_unclaim(dma_ch_samp_trig);
-
-	dma_timer_unclaim(dma_t_samp);
 
 	dma_ch_rx = -1;
 	dma_ch_cp = -1;
@@ -471,16 +430,46 @@ static void rf_rx_stop(void)
 	dma_ch_pio_sin = -1;
 	dma_ch_samp_cos = -1;
 	dma_ch_samp_sin = -1;
-	dma_ch_samp_trig = -1;
+}
 
-	dma_t_samp = -1;
+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];
+}
+
+inline static int nextI()
+{
+	static int prevI = 0;
+
+	int sI = 0;
+	sI -= 2 * pio_sm_get_blocking_unsafe(PIO, SM_COS);
+	sI -= pio_sm_get_blocking_unsafe(PIO, SM_COS);
+
+	int I = sI - prevI;
+	prevI = sI;
+
+	return I;
+}
+
+inline static int nextQ()
+{
+	static int prevQ = 0;
+
+	int sQ = 0;
+	sQ -= 2 * pio_sm_get_blocking_unsafe(PIO, SM_SIN);
+	sQ -= pio_sm_get_blocking_unsafe(PIO, SM_SIN);
+
+	int Q = sQ - prevQ;
+	prevQ = sQ;
+
+	return Q;
 }
 
 static void rf_rx(void)
 {
-	const uint32_t base = (uint32_t)rx_cos;
-	int pos = 0;
-
 	while (true) {
 		if (multicore_fifo_rvalid()) {
 			multicore_fifo_pop_blocking();
@@ -488,81 +477,25 @@ static void rf_rx(void)
 			return;
 		}
 
-		int head = (dma_hw->ch[dma_ch_in_cos].write_addr - base) / 4;
-		int delta = (head < pos ? head + RX_WORDS : head) - pos;
-
-		while (delta < RX_STRIDE) {
-			sleep_us(1);
-			head = (dma_hw->ch[dma_ch_in_cos].write_addr - base) / 4;
-			delta = (head < pos ? head + RX_WORDS : head) - pos;
-		}
-
-		const uint32_t *cos_ptr = rx_cos + pos;
-		const uint32_t *sin_ptr = rx_sin + pos;
-
-		pos = (pos + RX_STRIDE) & (RX_WORDS - 1);
-
 		uint8_t *block = iq_queue_buffer[iq_queue_pos];
 		uint8_t *blockptr = block;
 
-		/*
-		 * Since every 2 samples add to either +1 or -1,
-		 * the maximum amplitude in one direction is 1/2.
-		 */
-		int64_t max_amplitude = CLK_SYS_HZ / 2;
-
-		/*
-		 * Since the waveform is normally half of the time
-		 * above zero, we can halve once more.
-		 *
-		 * This is not perfect, so we do not max out the base
-		 * gain but keep it slightly below the maximum to make
-		 * sure we do not overshoot often.
-		 */
-		max_amplitude /= 2;
-
-		/*
-		 * We are allowing the counters to only go as high
-		 * as sampling rate.
-		 */
-		max_amplitude /= sample_rate;
-
 		for (int i = 0; i < IQ_SAMPLES; i++) {
-			int sI = 0, sQ = 0;
+			int I = 0, Q = 0;
 
-			/*
+			Q += nextQ();
-			 * I: +I1 -I3 +Q2 -Q4
+			I += nextI();
-			 * Q: +Q1 -Q3 -I2 +I4
-			 */
-			sI += *cos_ptr++;
-			sI -= *cos_ptr++;
 
-			sQ -= *cos_ptr++;
+			I -= nextQ();
-			sQ += *cos_ptr++;
+			Q += nextI();
 
-			sI -= *cos_ptr++;
+			Q -= nextQ();
-			sI += *cos_ptr++;
+			I -= nextI();
 
-			sQ += *cos_ptr++;
+			I += nextQ();
-			sQ -= *cos_ptr++;
+			Q -= nextI();
 
-			sQ += *sin_ptr++;
+			I *= gain;
-			sQ -= *sin_ptr++;
-
-			sI += *sin_ptr++;
-			sI -= *sin_ptr++;
-
-			sQ -= *sin_ptr++;
-			sQ += *sin_ptr++;
-
-			sI -= *sin_ptr++;
-			sI += *sin_ptr++;
-
-			int64_t I = sI;
-			int64_t Q = sQ;
-
-			I *= 127;
-			I -= (max_amplitude * 181) / 256;
 			I /= max_amplitude;
 
 			if (I > 127)
@@ -572,8 +505,7 @@ static void rf_rx(void)
 
 			*blockptr++ = (uint8_t)I + 128;
 
-			Q *= 127;
+			Q *= gain;
-			Q -= (max_amplitude * 181) / 256;
 			Q /= max_amplitude;
 
 			if (Q > 127)
@@ -587,12 +519,6 @@ static void rf_rx(void)
 		if (queue_try_add(&iq_queue, &block)) {
 			iq_queue_pos = (iq_queue_pos + 1) & (IQ_QUEUE_LEN - 1);
 		}
-
-		/* Randomize LO phase in the next word. */
-		for (int i = 0; i < 8; i++) {
-			lo_tweak(lo_cos, COS_PHASE);
-			lo_tweak(lo_sin, SIN_PHASE);
-		}
 	}
 }
 
@@ -600,18 +526,21 @@ static void run_command(uint8_t cmd, uint32_t arg)
 {
 	if (0x01 == cmd) {
 		/* Tune to a new center frequency */
-		rx_lo_init(arg - sample_rate, true);
+		frequency = arg;
+		rx_lo_init(frequency + sample_rate, true);
 	} else if (0x02 == cmd) {
 		/* Set the rate at which IQ sample pairs are sent */
 		sample_rate = arg;
+		max_amplitude = CLK_SYS_HZ / sample_rate / 2;
 		dma_timer_set_fraction(dma_t_samp, 1, CLK_SYS_HZ / (sample_rate * DECIMATE));
-		rx_lo_init(arg - sample_rate, true);
+		rx_lo_init(frequency + sample_rate, true);
 	} else if (0x04 == cmd) {
 		/* Set the tuner gain level */
-		bias_set_gain((arg + 14) / 30);
+		gain = INIT_GAIN * pow(10.0, arg / 200.0);
 	} else if (0x0d == cmd) {
 		/* Set tuner gain by the tuner's gain index */
-		bias_set_gain((gains[arg] + 14) / 30);
+		if (arg <= NUM_GAINS)
+			gain = INIT_GAIN * pow(10.0, gains[arg] / 200.0);
 	}
 }
 
@@ -639,41 +568,18 @@ static int check_command(void)
 	return -1;
 }
 
-static void do_rx(int rx_pin, int bias_pin)
+static void do_rx()
 {
-	rf_rx_start(rx_pin, bias_pin);
-	sleep_us(100);
-
-	dma_ch_in_cos = dma_claim_unused_channel(true);
-	dma_ch_in_sin = dma_claim_unused_channel(true);
-
-	dma_channel_config dma_conf;
-
-	dma_conf = dma_channel_get_default_config(dma_ch_in_cos);
-	channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_32);
-	channel_config_set_read_increment(&dma_conf, false);
-	channel_config_set_write_increment(&dma_conf, true);
-	channel_config_set_ring(&dma_conf, true, RX_BITS_DEPTH);
-	channel_config_set_dreq(&dma_conf, pio_get_dreq(pio1, 2, false));
-	channel_config_set_chain_to(&dma_conf, dma_ch_in_sin);
-	dma_channel_configure(dma_ch_in_cos, &dma_conf, rx_cos, &pio1->rxf[2], 2, false);
-
-	dma_conf = dma_channel_get_default_config(dma_ch_in_sin);
-	channel_config_set_transfer_data_size(&dma_conf, DMA_SIZE_32);
-	channel_config_set_read_increment(&dma_conf, false);
-	channel_config_set_write_increment(&dma_conf, true);
-	channel_config_set_ring(&dma_conf, true, RX_BITS_DEPTH);
-	channel_config_set_dreq(&dma_conf, pio_get_dreq(pio1, 3, false));
-	channel_config_set_chain_to(&dma_conf, dma_ch_in_cos);
-	dma_channel_configure(dma_ch_in_sin, &dma_conf, rx_sin, &pio1->rxf[3], 2, true);
-
-	multicore_launch_core1(rf_rx);
-
 	const uint8_t *block;
 
 	while (queue_try_remove(&iq_queue, &block))
 		/* Flush the queue */;
 
+	rf_rx_start();
+	sleep_us(100);
+
+	multicore_launch_core1(rf_rx);
+
 	while (true) {
 		int cmd;
 
@@ -684,25 +590,21 @@ static void do_rx(int rx_pin, int bias_pin)
 		if (queue_try_remove(&iq_queue, &block)) {
 			fwrite(block, IQ_BLOCK_LEN, 1, stdout);
 			fflush(stdout);
+		} else {
+			int wait = rnd_next() & 0x1fff;
+
+			for (int i = 0; i < wait; i++)
+				asm volatile("nop");
 		}
 	}
 
 done:
 	multicore_fifo_push_blocking(0);
 	multicore_fifo_pop_blocking();
-	sleep_us(10);
+	sleep_us(100);
 	multicore_reset_core1();
 
 	rf_rx_stop();
-
-	dma_channel_abort(dma_ch_in_cos);
-	dma_channel_abort(dma_ch_in_sin);
-	dma_channel_cleanup(dma_ch_in_cos);
-	dma_channel_cleanup(dma_ch_in_sin);
-	dma_channel_unclaim(dma_ch_in_cos);
-	dma_channel_unclaim(dma_ch_in_sin);
-	dma_ch_in_cos = -1;
-	dma_ch_in_sin = -1;
 }
 
 int main()
@@ -717,6 +619,7 @@ int main()
 	gpio_set_dir(PSU_PIN, GPIO_OUT);
 	gpio_put(PSU_PIN, 1);
 
+	/* Prioritize DMA over CPU. */
 	bus_ctrl_hw->priority |= BUSCTRL_BUS_PRIORITY_DMA_W_BITS | BUSCTRL_BUS_PRIORITY_DMA_R_BITS;
 
 	stdio_usb_init();
@@ -724,7 +627,11 @@ int main()
 
 	queue_init(&iq_queue, sizeof(uint8_t *), IQ_QUEUE_LEN);
 
-	rx_lo_init(INIT_FREQ - INIT_SAMPLE_RATE, true);
+	rx_lo_init(frequency + sample_rate, true);
+
+	/* We need to have the sampling timer ready. */
+	dma_t_samp = dma_claim_unused_timer(true);
+	dma_timer_set_fraction(dma_t_samp, 1, CLK_SYS_HZ / (sample_rate * DECIMATE));
 
 	while (true) {
 		if (check_command() > 0) {
@@ -734,7 +641,7 @@ int main()
 			fwrite(header, sizeof header, 1, stdout);
 			fflush(stdout);
 
-			do_rx(10, 11);
+			do_rx();
 		}
 
 		sleep_ms(10);

src/vendor/pico-stdio-usb-simple

@@ -1 +1 @@
-Subproject commit b6b09e34b844326a156bc6734146a88111138473
+Subproject commit ed4858dda407ec66626aade9b7c6ad6016539f4c