mordae/pico-sdr
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Improve gain handling

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Now it's possible to set gain in gqrx.
This commit is contained in:
Jan Hamal Dvořák 2024-06-06 22:54:02 +02:00
parent 40a0b843fb
commit a2104495c6
1 changed files with 21 additions and 5 deletions

26
src/main.c
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@ -40,11 +40,15 @@ static uint32_t lo_sin[LO_WORDS] __attribute__((__aligned__(1 << LO_BITS_DEPTH))
#define RX_STRIDE (2 * IQ_SAMPLES) #define RX_STRIDE (2 * IQ_SAMPLES)
#define RX_BITS_DEPTH 12 #define RX_BITS_DEPTH 12
#define RX_WORDS (1 << (RX_BITS_DEPTH - 2)) #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_cos[RX_WORDS] __attribute__((__aligned__(1 << RX_BITS_DEPTH)));
static uint32_t rx_sin[RX_WORDS] __attribute__((__aligned__(1 << RX_BITS_DEPTH))); static uint32_t rx_sin[RX_WORDS] __attribute__((__aligned__(1 << RX_BITS_DEPTH)));
#define INIT_GAIN 256 #define INIT_GAIN 120
#define INIT_SAMPLE_RATE 100000 #define INIT_SAMPLE_RATE 100000
#define INIT_FREQ 94600000
#define NUM_GAINS 29 #define NUM_GAINS 29
static int gains[NUM_GAINS] = { 0, 9, 14, 27, 37, 77, 87, 125, 144, 157, static int gains[NUM_GAINS] = { 0, 9, 14, 27, 37, 77, 87, 125, 144, 157,
@ -457,11 +461,13 @@ static void rf_rx(void)
/* /*
* Since the waveform is normally half of the time * Since the waveform is normally half of the time
* above zero, we could halve once more. * above zero, we can halve once more.
* *
* Instead we use 2/3 to provide 1/3 reserve. * 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 = max_amplitude * 2 / 3; max_amplitude = max_amplitude / 2;
/* /*
* We are allowing the counters to only go as high * We are allowing the counters to only go as high
@ -482,6 +488,11 @@ static void rf_rx(void)
I *= gain; I *= gain;
I /= max_amplitude; I /= max_amplitude;
if (I > 127)
I = 127;
else if (I < -128)
I = -128;
*blockptr++ = I + 128; *blockptr++ = I + 128;
uint32_t sin_neg = *sin_ptr++; uint32_t sin_neg = *sin_ptr++;
@ -496,7 +507,12 @@ static void rf_rx(void)
Q *= gain; Q *= gain;
Q /= max_amplitude; Q /= max_amplitude;
*blockptr++ = Q + 128; if (Q > 127)
Q = 127;
else if (Q < -128)
Q = -128;
*blockptr++ = (uint8_t)Q + 128;
} }
(void)queue_try_add(&iq_queue, block); (void)queue_try_add(&iq_queue, block);