diff --git a/grc/PicoSDR-WBFM.grc b/grc/PicoSDR-WBFM.grc
index c9d33cc..6be09c4 100644
--- a/grc/PicoSDR-WBFM.grc
+++ b/grc/PicoSDR-WBFM.grc
@@ -37,7 +37,7 @@ blocks:
id: variable
parameters:
comment: ''
- value: '94_600_000'
+ value: '88_200_000'
states:
bus_sink: false
bus_source: false
@@ -49,7 +49,7 @@ blocks:
id: variable
parameters:
comment: ''
- value: '192_000'
+ value: '200_000'
states:
bus_sink: false
bus_source: false
@@ -78,7 +78,7 @@ blocks:
parameters:
affinity: ''
alias: ''
- audio_decimation: '4'
+ audio_decimation: '8'
comment: ''
deemph_tau: 75e-6
maxoutbuf: '0'
@@ -100,7 +100,7 @@ blocks:
device_name: ''
num_inputs: '2'
ok_to_block: 'True'
- samp_rate: samp_rate // 4
+ samp_rate: samp_rate // 8
states:
bus_sink: false
bus_source: false
@@ -150,15 +150,15 @@ blocks:
alias: ''
beta: '6.76'
comment: ''
- cutoff_freq: samp_rate / 8
- decim: '4'
+ cutoff_freq: samp_rate / 16
+ decim: '8'
gain: '1'
interp: '1'
maxoutbuf: '0'
minoutbuf: '0'
samp_rate: samp_rate
type: fir_filter_fff
- width: samp_rate / 8
+ width: samp_rate / 16
win: window.WIN_HAMMING
states:
bus_sink: false
@@ -677,7 +677,7 @@ blocks:
name: '"FM Demodulation"'
nconnections: '1'
size: '512'
- srate: samp_rate // (2 ** 3)
+ srate: samp_rate // 8
stemplot: 'False'
style1: '1'
style10: '1'
@@ -856,4 +856,4 @@ connections:
metadata:
file_format: 1
- grc_version: 3.10.9.2
+ grc_version: 3.10.11.0
diff --git a/src/main.c b/src/main.c
index b654e0f..8fcbf11 100644
--- a/src/main.c
+++ b/src/main.c
@@ -53,27 +53,28 @@ static uint32_t lo_sin[LO_WORDS] __attribute__((__aligned__(1 << LO_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 };
+#define BASE_GAIN (1 << 15)
+#define ATTN_BITS 8
+
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 gain = BASE_GAIN / (CLK_SYS_HZ / INIT_SAMPLE_RATE / 2);
static int frequency = INIT_FREQ;
static queue_t iq_queue;
static uint8_t iq_queue_buffer[IQ_QUEUE_LEN][IQ_BLOCK_LEN];
static size_t iq_queue_pos = 0;
-static uint32_t rnd = 0;
+static uint32_t xorshift_seed;
-inline static __unused uint32_t rnd_next()
+static inline __unused uint32_t xorshift(void)
{
- rnd = rnd * 0x41c64e6d + 12345;
- return rnd;
+ uint32_t x = xorshift_seed;
+ x ^= x << 13;
+ x ^= x >> 17;
+ x ^= x << 5;
+ xorshift_seed = x;
+ return x;
}
static void dma_channel_clear_chain_to(int ch)
@@ -187,6 +188,7 @@ static const uint32_t samp_insn = 16;
static void init_adder()
{
const uint16_t insn[] = {
+ /* y has weight of 2, x has weight of 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
@@ -428,6 +430,11 @@ static void rf_rx_stop(void)
dma_ch_samp_sin = -1;
}
+inline static void led_set(bool 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)))
@@ -438,12 +445,18 @@ inline static uint32_t pio_sm_get_blocking_unsafe(pio_hw_t *pio, int sm)
inline static int nextI()
{
- static int prevI = 0;
+ static int prevI2, prevI1, prevI;
- int sI = 0;
- sI -= 2 * pio_sm_get_blocking_unsafe(PIO, SM_COS);
- sI -= pio_sm_get_blocking_unsafe(PIO, SM_COS);
+ int sI2 = pio_sm_get_blocking_unsafe(PIO, SM_COS);
+ int I2 = sI2 - prevI2;
+ prevI2 = sI2;
+
+ int sI1 = pio_sm_get_blocking_unsafe(PIO, SM_COS);
+ int I1 = sI1 - prevI1;
+ prevI1 = sI1;
+
+ int sI = I2 + I2 + I1;
int I = sI - prevI;
prevI = sI;
@@ -452,12 +465,18 @@ inline static int nextI()
inline static int nextQ()
{
- static int prevQ = 0;
+ static int prevQ2, prevQ1, prevQ;
- int sQ = 0;
- sQ -= 2 * pio_sm_get_blocking_unsafe(PIO, SM_SIN);
- sQ -= pio_sm_get_blocking_unsafe(PIO, SM_SIN);
+ int sQ2 = pio_sm_get_blocking_unsafe(PIO, SM_SIN);
+ int Q2 = sQ2 - prevQ2;
+ prevQ2 = sQ2;
+
+ int sQ1 = pio_sm_get_blocking_unsafe(PIO, SM_SIN);
+ int Q1 = sQ1 - prevQ1;
+ prevQ1 = sQ1;
+
+ int sQ = Q2 + Q2 + Q1;
int Q = sQ - prevQ;
prevQ = sQ;
@@ -492,28 +511,21 @@ static void rf_rx(void)
Q -= nextI();
I *= gain;
- I /= max_amplitude;
+ I >>= ATTN_BITS;
- if (I > 127)
- I = 127;
- else if (I < -128)
- I = -128;
-
- *blockptr++ = (uint8_t)I + 128;
+ *blockptr++ = I + 128;
Q *= gain;
- Q /= max_amplitude;
+ Q >>= ATTN_BITS;
- if (Q > 127)
- Q = 127;
- else if (Q < -128)
- Q = -128;
-
- *blockptr++ = (uint8_t)Q + 128;
+ *blockptr++ = Q + 128;
}
if (queue_try_add(&iq_queue, &block)) {
- iq_queue_pos = (iq_queue_pos + 1) & (IQ_QUEUE_LEN - 1);
+ iq_queue_pos = (iq_queue_pos + 1) % IQ_QUEUE_LEN;
+ led_set(0);
+ } else {
+ led_set(1);
}
}
}
@@ -527,16 +539,9 @@ 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;
- max_amplitude = CLK_SYS_HZ / sample_rate / 2;
+ gain = BASE_GAIN / (CLK_SYS_HZ / sample_rate / 2);
dma_timer_set_fraction(dma_t_samp, 1, CLK_SYS_HZ / (sample_rate * DECIMATE));
rx_lo_init(frequency + sample_rate, true);
- } else if (0x04 == cmd) {
- /* Set the tuner gain level */
- gain = INIT_GAIN * pow(10.0, arg / 200.0);
- } else if (0x0d == cmd) {
- /* Set tuner gain by the tuner's gain index */
- if (arg <= NUM_GAINS)
- gain = INIT_GAIN * pow(10.0, gains[arg] / 200.0);
}
}
@@ -587,7 +592,7 @@ static void do_rx()
fwrite(block, IQ_BLOCK_LEN, 1, stdout);
fflush(stdout);
} else {
- int wait = rnd_next() & 0x1fff;
+ int wait = xorshift() >> (32 - 15);
for (int i = 0; i < wait; i++)
asm volatile("nop");
@@ -615,6 +620,10 @@ int main()
gpio_set_dir(PSU_PIN, GPIO_OUT);
gpio_put(PSU_PIN, 1);
+ gpio_init(PICO_DEFAULT_LED_PIN);
+ gpio_set_dir(PICO_DEFAULT_LED_PIN, GPIO_OUT);
+ gpio_put(PICO_DEFAULT_LED_PIN, 0);
+
/* Prioritize DMA over CPU. */
bus_ctrl_hw->priority |= BUSCTRL_BUS_PRIORITY_DMA_W_BITS | BUSCTRL_BUS_PRIORITY_DMA_R_BITS;
@@ -633,7 +642,7 @@ int main()
if (check_command() > 0) {
static const uint32_t header[3] = { __builtin_bswap32(0x52544c30),
__builtin_bswap32(5),
- __builtin_bswap32(NUM_GAINS) };
+ __builtin_bswap32(29) };
fwrite(header, sizeof header, 1, stdout);
fflush(stdout);