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extmod/machine_spi: Add optional support for fast software SPI. 

If a port defines MICROPY_PY_MACHINE_SPI_MIN_DELAY then it can use a
faster software SPI loop that does not make calls to the delay_us
function.
This commit is contained in:
Damien George 2016-10-04 13:46:40 +11:00
parent b932b2dd1f
commit b0eb0d6153
1 changed files with 22 additions and 0 deletions
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22
extmod/machine_spi.c
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@ -38,6 +38,28 @@ void mp_machine_soft_spi_transfer(mp_obj_base_t *self_in, size_t len, const uint
// only MSB transfer is implemented
// If a port defines MICROPY_PY_MACHINE_SPI_MIN_DELAY, and the configured
// delay_half is equal to this value, then the software SPI implementation
// will run as fast as possible, limited only by CPU speed and GPIO time.
#ifdef MICROPY_PY_MACHINE_SPI_MIN_DELAY
if (delay_half == MICROPY_PY_MACHINE_SPI_MIN_DELAY) {
for (size_t i = 0; i < len; ++i) {
uint8_t data_out = src[i];
uint8_t data_in = 0;
for (int j = 0; j < 8; ++j, data_out <<= 1) {
mp_hal_pin_write(self->mosi, (data_out >> 7) & 1);
mp_hal_pin_write(self->sck, 1 - self->polarity);
data_in = (data_in << 1) | mp_hal_pin_read(self->miso);
mp_hal_pin_write(self->sck, self->polarity);
}
if (dest != NULL) {
dest[i] = data_in;
}
}
return;
}
#endif
for (size_t i = 0; i < len; ++i) {
uint8_t data_out = src[i];
uint8_t data_in = 0;