mordae/pico-sdr
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Prevent overflow with jittery sampling

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This commit is contained in:
Jan Hamal Dvořák 2024-03-01 14:44:13 +01:00
parent 31d7a8c613
commit 17389d28c4
1 changed files with 6 additions and 3 deletions

9
src/main.c
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@ -556,8 +556,10 @@ static void rf_tx_stop()
static void rf_rx(void) static void rf_rx(void)
{ {
const int amp_max = CLK_SYS_HZ / 2 / BANDWIDTH * DECIMATION + 16; const int amp_max = CLK_SYS_HZ / 2 / BANDWIDTH * DECIMATION;
const int amp_scale = INT_MAX / amp_max;
/* Scale down 2× to accomodate for jitter. */
const int amp_scale = INT_MAX / amp_max / 2;
static int8_t block[IQ_BLOCK_LEN]; static int8_t block[IQ_BLOCK_LEN];
uint32_t prev_transfers = dma_hw->ch[dma_ch_in_cos].transfer_count; uint32_t prev_transfers = dma_hw->ch[dma_ch_in_cos].transfer_count;
@ -788,7 +790,8 @@ static void do_rx(int rx_pin, int bias_pin, float freq, char mode)
fwrite(block, sizeof block, 1, stdout); fwrite(block, sizeof block, 1, stdout);
fflush(stdout); fflush(stdout);
} else { } else {
float rssi = 10.0f * log10f(powf((float)agc / (float)INT_MAX, 2)); float rssi =
10.0f * log10f(powf((float)agc / (float)INT_MAX * 2, 2));
for (int i = 0; i < IQ_BLOCK_LEN / 2; i += 8) { for (int i = 0; i < IQ_BLOCK_LEN / 2; i += 8) {
int I = block[i * 2]; int I = block[i * 2];