Fix initial frequency

src/main.c

@@ -22,10 +22,10 @@
 #include <stdlib.h>
 
 #define VREG_VOLTAGE VREG_VOLTAGE_1_20
-#define CLK_SYS_HZ (300 * MHZ)
+#define CLK_SYS_HZ (288 * MHZ)
 
 #define LO_PIN 9
-#define RX_PIN 8
+#define RX_PIN 13
 #define FB_PIN 5
 #define PSU_PIN 23
 
@@ -51,9 +51,9 @@ static uint32_t lo_phase[LO_NUM_PHASES][LO_PHASE_WORDS]
 static const uint32_t *lo_cos_phases[LO_COS_PHASES]
 	__attribute__((__aligned__(1 << LO_PHASE_BITS)));
 
-#define DECIMATE 4
+#define DECIMATE 16
 #define RX_STRIDE (2 * IQ_SAMPLES * DECIMATE)
-#define RX_BITS_DEPTH 13
+#define RX_BITS_DEPTH 14
 #define RX_WORDS (1 << (RX_BITS_DEPTH - 2))
 
 static_assert(RX_STRIDE * 4 <= RX_WORDS, "RX_STRIDE * 4 <= RX_WORDS");
@@ -69,6 +69,7 @@ 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 dc_level = CLK_SYS_HZ / INIT_SAMPLE_RATE / 2;
 static int gain = INIT_GAIN;
 
 static int dma_ch_rx1 = -1;
@@ -108,8 +109,8 @@ static void init_lo()
 	gpio_disable_pulls(LO_PIN);
 	pio_gpio_init(PIO, LO_PIN);
 
-	gpio_set_drive_strength(LO_PIN, GPIO_DRIVE_STRENGTH_2MA);
+	gpio_set_drive_strength(LO_PIN, GPIO_DRIVE_STRENGTH_12MA);
-	gpio_set_slew_rate(LO_PIN, GPIO_SLEW_RATE_SLOW);
+	gpio_set_slew_rate(LO_PIN, GPIO_SLEW_RATE_FAST);
 
 	const uint16_t insn[] = {
 		pio_encode_out(pio_pindirs, 1),
@@ -218,23 +219,34 @@ static void init_rx()
 static void init_ad()
 {
 	const uint16_t insn[] = {
-		pio_encode_jmp_y_dec(1),
+		pio_encode_out(pio_pc, 4), // 0000 +0
-		pio_encode_out(pio_pc, 2),
+		pio_encode_jmp_x_dec(0),   // 0001 +1
-		pio_encode_out(pio_pc, 2),
+		pio_encode_jmp_x_dec(0),   // 0010 +1
-		pio_encode_jmp_x_dec(2),
+		pio_encode_jmp_y_dec(0),   // 0011 +2
-
+		pio_encode_jmp_x_dec(0),   // 0100 +1
-		/* Avoid Y-- on wrap. */
+		pio_encode_jmp_y_dec(0),   // 0101 +2
-		pio_encode_out(pio_pc, 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
 
 		/*
 		 * Should wrap here.
 		 * Jump to this portion must be inserted from the outside.
 		 */
-		pio_encode_in(pio_x, 32),
 		pio_encode_in(pio_y, 32),
-		pio_encode_set(pio_x, 0),
+		pio_encode_in(pio_x, 32),
 		pio_encode_set(pio_y, 0),
-		pio_encode_out(pio_pc, 2),
+		pio_encode_set(pio_x, 0),
+		pio_encode_jmp_y_dec(21),
+		pio_encode_jmp_x_dec(22),
+		pio_encode_out(pio_pc, 4),
 	};
 
 	pio_program_t prog = {
@@ -250,11 +262,11 @@ static void init_ad()
 		pio_add_program(PIO, &prog);
 
 	pio_sm_config pc = pio_get_default_sm_config();
-	sm_config_set_wrap(&pc, prog.origin, prog.origin + 5 - 1);
+	sm_config_set_wrap(&pc, prog.origin, prog.origin + 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(PIO, AD_SM, prog.origin + 1, &pc);
+	pio_sm_init(PIO, AD_SM, prog.origin, &pc);
 }
 
 #define STEP_BASE ((UINT_MAX + 1.0) / CLK_SYS_HZ)
@@ -297,7 +309,7 @@ static void rx_lo_init(double req_freq, bool align)
 	}
 }
 
-static const uint32_t samp_insn = 5;
+static const uint32_t samp_insn = 16;
 
 static void rf_rx_start()
 {
@@ -363,10 +375,10 @@ static void rf_rx_start()
 	dma_channel_configure(dma_ch_samp_cos, &dma_conf, &PIO->sm[AD_SM].instr, &samp_insn,
 			      UINT_MAX, false);
 
+	init_ad();
 	init_lo();
 	init_fb();
 	init_rx();
-	init_ad();
 
 	dma_channel_start(dma_ch_rx1);
 	dma_channel_start(dma_ch_mix1);
@@ -422,50 +434,61 @@ struct IQ {
 
 inline static struct IQ next_sample(const uint32_t *buf)
 {
-	static int h[11];
+	int x15 = gain * (-2 * buf[0] - buf[1] - dc_level);
-
+	int x14 = gain * (-2 * buf[2] - buf[3] - dc_level);
-	int x3 = buf[0] - buf[1];
+	int x13 = gain * (-2 * buf[4] - buf[5] - dc_level);
-	int x2 = buf[2] - buf[3];
+	int x12 = gain * (-2 * buf[6] - buf[7] - dc_level);
-	int x1 = buf[5] - buf[4];
+	int x11 = gain * (-2 * buf[8] - buf[9] - dc_level);
-	int x0 = buf[7] - buf[6];
+	int x10 = gain * (-2 * buf[10] - buf[11] - dc_level);
-
+	int x09 = gain * (-2 * buf[12] - buf[13] - dc_level);
-	const int c[] = { 4, 2, -8, -9, 19, 55 };
+	int x08 = gain * (-2 * buf[14] - buf[15] - dc_level);
+	int x07 = gain * (-2 * buf[16] - buf[17] - dc_level);
+	int x06 = gain * (-2 * buf[18] - buf[19] - dc_level);
+	int x05 = gain * (-2 * buf[20] - buf[21] - dc_level);
+	int x04 = gain * (-2 * buf[22] - buf[23] - dc_level);
+	int x03 = gain * (-2 * buf[24] - buf[25] - dc_level);
+	int x02 = gain * (-2 * buf[26] - buf[27] - dc_level);
+	int x01 = gain * (-2 * buf[28] - buf[29] - dc_level);
+	int x00 = gain * (-2 * buf[30] - buf[31] - dc_level);
 
 	int I = 0, Q = 0;
 
-	Q += (c[0]) * h[10];
+	I += 93 * x15;
-	I += (c[0] + c[1]) * h[9];
+	I += 71 * x14;
-	Q += (c[0] + c[1] + c[2]) * h[8];
+	I += 39 * x13;
-	I += (c[0] + c[1] + c[2] + c[3]) * h[7];
+	I += 0 * x12;
-	Q += (c[1] + c[2] + c[3] + c[4]) * h[6];
+	I += -39 * x11;
-	I += (c[2] + c[3] + c[4] + c[5]) * h[5];
+	I += -71 * x10;
-	Q += (c[3] + c[4] + c[5] + c[5]) * h[4];
+	I += -93 * x09;
-	I += (c[4] + c[5] + c[5] + c[4]) * h[3];
+	I += -101 * x08;
-	Q += (c[5] + c[5] + c[4] + c[3]) * h[2];
+	I += -93 * x07;
-	I += (c[5] + c[4] + c[3] + c[2]) * h[1];
+	I += -71 * x06;
-	Q += (c[4] + c[3] + c[2] + c[1]) * h[0];
+	I += -39 * x05;
-	I += (c[3] + c[2] + c[1] + c[0]) * x3;
+	I += 0 * x04;
-	Q += (c[2] + c[1] + c[0]) * x2;
+	I += 39 * x03;
-	I += (c[1] + c[0]) * x1;
+	I += 71 * x02;
-	Q += (c[0]) * x0;
+	I += 93 * x01;
+	I += 101 * x00;
 
-	I *= gain;
+	Q += 39 * x15;
-	I /= 128;
+	Q += 71 * x14;
+	Q += 93 * x13;
+	Q += 101 * x12;
+	Q += 93 * x11;
+	Q += 71 * x10;
+	Q += 39 * x09;
+	Q += 0 * x08;
+	Q += -39 * x07;
+	Q += -71 * x06;
+	Q += -93 * x05;
+	Q += -101 * x04;
+	Q += -93 * x03;
+	Q += -71 * x02;
+	Q += -39 * x01;
+	Q += 0 * x00;
 
-	Q *= gain;
+	I /= 1024;
-	Q /= 128;
+	Q /= 1024;
-
-	h[10] = h[6];
-	h[9] = h[5];
-	h[8] = h[4];
-	h[7] = h[3];
-	h[6] = h[2];
-	h[5] = h[1];
-	h[4] = h[0];
-	h[3] = x3;
-	h[2] = x2;
-	h[1] = x1;
-	h[0] = x0;
 
 	return (struct IQ){ I, Q };
 }
@@ -502,23 +525,13 @@ static void rf_rx(void)
 		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.
-		 *
-		 * We are allowing the counters to only go as high
-		 * as sampling rate.
-		 */
-		int64_t max_amplitude = CLK_SYS_HZ / 2 / sample_rate;
-
 		for (int i = 0; i < IQ_SAMPLES; i++) {
 			struct IQ IQ = next_sample(cos_ptr);
 			int64_t I = IQ.I;
 			int64_t Q = IQ.Q;
 			cos_ptr += 2 * DECIMATE;
 
-			I -= (max_amplitude * 181) / 256;
+			I /= dc_level;
-			I /= max_amplitude;
 
 			if (I > 127)
 				I = 127;
@@ -527,8 +540,7 @@ static void rf_rx(void)
 
 			*blockptr++ = (uint8_t)I + 128;
 
-			Q -= (max_amplitude * 181) / 256;
+			Q /= dc_level;
-			Q /= max_amplitude;
 
 			if (Q > 127)
 				Q = 127;
@@ -552,6 +564,7 @@ static void run_command(uint8_t cmd, uint32_t arg)
 	} else if (0x02 == cmd) {
 		/* Set the rate at which IQ sample pairs are sent */
 		sample_rate = arg;
+		dc_level = 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);
 	} else if (0x04 == cmd) {
@@ -667,7 +680,7 @@ int main()
 
 	queue_init(&iq_queue, sizeof(uint8_t *), IQ_QUEUE_LEN);
 
-	rx_lo_init(INIT_FREQ - INIT_SAMPLE_RATE, true);
+	rx_lo_init(INIT_FREQ + INIT_SAMPLE_RATE, true);
 
 	while (true) {
 		if (check_command() > 0) {

src/vendor/pico-stdio-usb-simple

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