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rp2pio: Transfer up to 32 bytes before checking background tasks

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@Jerryneedell noticed that this problem affected strips short enough
to not use the DMA peripheral, thanks for the hot tip!

Instead of checking for background tasks after every byte transfer,
try up to 32 transfers before attending to background tasks.

This fixes the problem I was seeing on my 5-pixel circuit.

Closes #4135.
This commit is contained in:
Jeff Epler 2021-02-08 08:35:07 -06:00
parent a10ce39ae6
commit 5423e4966c
1 changed files with 17 additions and 9 deletions
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8
ports/raspberrypi/common-hal/rp2pio/StateMachine.c
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@ -546,15 +546,23 @@ static bool _transfer(rp2pio_statemachine_obj_t *self,
size_t tx_remaining = out_len;
while (rx_remaining || tx_remaining) {
for (int i=0; i<32; i++) {
bool did_transfer = false;
if (tx_remaining && !pio_sm_is_tx_fifo_full(self->pio, self->state_machine)) {
*tx_destination = *data_out;
data_out++;
--tx_remaining;
did_transfer = true;
}
if (rx_remaining && !pio_sm_is_rx_fifo_empty(self->pio, self->state_machine)) {
*data_in = (uint8_t) *rx_source;
data_in++;
--rx_remaining;
did_transfer = true;
}
if (!did_transfer) {
break;
}
}
RUN_BACKGROUND_TASKS;
if (mp_hal_is_interrupted()) {