mordae/pico-sdr
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Avoid 64-bit integers as much as possible

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This commit is contained in:
Jan Hamal Dvořák 2024-02-26 22:23:32 +01:00
parent d26db812fa
commit 1003d29c2e
1 changed files with 42 additions and 35 deletions

77
src/main.c
View file

@ -40,7 +40,6 @@
#define CLK_SYS_HZ (250 * MHZ) #define CLK_SYS_HZ (250 * MHZ)
#define BANDWIDTH 1024000 #define BANDWIDTH 1024000
#define DECIMATION 64 #define DECIMATION 64
#define LPF_SIZE DECIMATION
#define IQ_BLOCK_LEN 64 #define IQ_BLOCK_LEN 64
@ -550,27 +549,30 @@ 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 + 1;
const int amp_scale = INT_MAX / amp_max;
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;
unsigned pos = 0; unsigned pos = 0;
static int lpIh1[LPF_SIZE]; static int lpIh1[DECIMATION];
static int lpQh1[LPF_SIZE]; static int lpQh1[DECIMATION];
int lpIa1 = 0; int lpIa1 = 0;
int lpQa1 = 0; int lpQa1 = 0;
static int lpIh2[LPF_SIZE]; static int lpIh2[DECIMATION];
static int lpQh2[LPF_SIZE]; static int lpQh2[DECIMATION];
int lpIa2 = 0; int lpIa2 = 0;
int lpQa2 = 0; int lpQa2 = 0;
static int lpIh3[LPF_SIZE]; static int lpIh3[DECIMATION];
static int lpQh3[LPF_SIZE]; static int lpQh3[DECIMATION];
int lpIa3 = 0; int lpIa3 = 0;
int lpQa3 = 0; int lpQa3 = 0;
int64_t dcI = 0, dcQ = 0; int64_t dcI = 0, dcQ = 0;
int64_t agc = 0; int agc = 0;
while (true) { while (true) {
if (multicore_fifo_rvalid()) { if (multicore_fifo_rvalid()) {
@ -597,8 +599,8 @@ static void rf_rx(void)
pos = (pos + 2 * DECIMATION) & (RX_WORDS - 1); pos = (pos + 2 * DECIMATION) & (RX_WORDS - 1);
int64_t dI = 0; int dI = 0;
int64_t dQ = 0; int dQ = 0;
for (int d = 0; d < DECIMATION; d++) { for (int d = 0; d < DECIMATION; d++) {
uint32_t cos_pos = *cos_ptr++; uint32_t cos_pos = *cos_ptr++;
@ -609,10 +611,11 @@ static void rf_rx(void)
int I = cos_neg - cos_pos; int I = cos_neg - cos_pos;
int Q = sin_neg - sin_pos; int Q = sin_neg - sin_pos;
I <<= 8; /* Scale up before filtering. */
Q <<= 8; I = I * amp_scale;
Q = Q * amp_scale;
int lpP = d & (LPF_SIZE - 1); int lpP = d & (DECIMATION - 1);
lpIa1 += I - lpIh1[lpP]; lpIa1 += I - lpIh1[lpP];
lpQa1 += Q - lpQh1[lpP]; lpQa1 += Q - lpQh1[lpP];
@ -620,8 +623,8 @@ static void rf_rx(void)
lpIh1[lpP] = I; lpIh1[lpP] = I;
lpQh1[lpP] = Q; lpQh1[lpP] = Q;
I = lpIa1 / LPF_SIZE; I = lpIa1 / DECIMATION;
Q = lpQa1 / LPF_SIZE; Q = lpQa1 / DECIMATION;
lpIa2 += I - lpIh2[lpP]; lpIa2 += I - lpIh2[lpP];
lpQa2 += Q - lpQh2[lpP]; lpQa2 += Q - lpQh2[lpP];
@ -629,8 +632,8 @@ static void rf_rx(void)
lpIh2[lpP] = I; lpIh2[lpP] = I;
lpQh2[lpP] = Q; lpQh2[lpP] = Q;
I = lpIa2 / LPF_SIZE; I = lpIa2 / DECIMATION;
Q = lpQa2 / LPF_SIZE; Q = lpQa2 / DECIMATION;
lpIa3 += I - lpIh3[lpP]; lpIa3 += I - lpIh3[lpP];
lpQa3 += Q - lpQh3[lpP]; lpQa3 += Q - lpQh3[lpP];
@ -638,35 +641,39 @@ static void rf_rx(void)
lpIh3[lpP] = I; lpIh3[lpP] = I;
lpQh3[lpP] = Q; lpQh3[lpP] = Q;
I = lpIa3 / LPF_SIZE; I = lpIa3 / DECIMATION;
Q = lpQa3 / LPF_SIZE; Q = lpQa3 / DECIMATION;
I >>= 8;
Q >>= 8;
dI += I; dI += I;
dQ += Q; dQ += Q;
} }
dcI = ((dcI << 13) - dcI + (dI << 19)) >> 13; /*
dcQ = ((dcQ << 13) - dcQ + (dQ << 19)) >> 13; * Original dI/dQ are scaled to 32 bits.
* These are part of DC removal alpha.
*/
int64_t dI19 = (int64_t)dI << 19;
int64_t dQ19 = (int64_t)dQ << 19;
dI = ((dI << 19) - dcI) >> 19; dcI = ((dcI << 13) - dcI + dI19) >> 13;
dQ = ((dQ << 19) - dcQ) >> 19; dcQ = ((dcQ << 13) - dcQ + dQ19) >> 13;
dI <<= 16; dI = (dI19 - dcI) >> 19;
dQ <<= 16; dQ = (dQ19 - dcQ) >> 19;
agc = (agc * UINT16_MAX) >> 16; /* Slowly decay AGC amplitude. */
agc -= (agc >> 16) | 1;
if (llabs(dI) > agc) if (abs(dI) > agc)
agc = llabs(dI); agc = abs(dI);
if (llabs(dQ) > agc) if (abs(dQ) > agc)
agc = llabs(dQ); agc = abs(dQ);
*blockptr++ = 127 * dI / agc; int agc_div = (agc >> 7) + (agc >> 14);
*blockptr++ = 127 * dQ / agc;
*blockptr++ = dI / agc_div;
*blockptr++ = dQ / agc_div;
} }
if (!queue_try_add(&iq_queue, block)) { if (!queue_try_add(&iq_queue, block)) {