mordae/pico-sdr
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Avoid sleeps to prevent low-frequency artifacts

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Replace them with busy looks that do not lower the current draw.
It still prevent memory saturation as the loops do not touch memory.
This commit is contained in:
Jan Hamal Dvořák 2024-07-27 15:39:40 +02:00
parent 24d6acdb53
commit f5fb02c190
1 changed files with 18 additions and 5 deletions
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23
src/main.c
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@ -87,6 +87,14 @@ 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;
inline static __unused uint32_t rnd_next()
{
rnd = rnd * 0x41c64e6d + 12345;
return rnd;
}
static void dma_channel_clear_chain_to(int ch)
{
uint32_t ctrl = dma_hw->ch[ch].al1_ctrl;
@ -128,7 +136,7 @@ static void init_lo()
sm_config_set_out_shift(&pc, false, true, 32);
pio_sm_init(PIO, LO_SM, prog.origin, &pc);
pio_sm_set_consecutive_pindirs(PIO, LO_SM, LO_PIN, 1, GPIO_OUT);
pio_sm_set_consecutive_pindirs(PIO, LO_SM, LO_PIN, 1, GPIO_IN);
pio_sm_exec_wait_blocking(PIO, LO_SM, pio_encode_set(pio_pins, 0));
}
@ -477,10 +485,12 @@ static void rf_rx(void)
int head = (dma_hw->ch[dma_ch_in_cos].write_addr - base) / 4;
int delta = (head < pos ? head + RX_WORDS : head) - pos;
sleep_us(10);
while (delta < RX_STRIDE) {
sleep_us(1);
int wait = rnd_next() & 63;
for (int i = 0; i < wait; i++)
asm volatile("nop");
head = (dma_hw->ch[dma_ch_in_cos].write_addr - base) / 4;
delta = (head < pos ? head + RX_WORDS : head) - pos;
}
@ -616,7 +626,10 @@ static void do_rx()
fwrite(block, IQ_BLOCK_LEN, 1, stdout);
fflush(stdout);
} else {
sleep_us(25);
int wait = rnd_next() & 0x1fff;
for (int i = 0; i < wait; i++)
asm volatile("nop");
}
}