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Don't break transfer16 into 2 8-bit CS periods (#1764)

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With HW chip select enabled, transfer16's 2 individual byte transfers will
actualy deassert CS for a brief instant between bytes.  Avoid this by doing
a single multi-byte (2) tranfer of 16b.
This commit is contained in:
Earle F. Philhower, III 2023-10-11 08:40:17 -07:00 committed by GitHub
parent 5ecef160d4
commit 5678bb9904
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 5 additions and 6 deletions
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11
libraries/SPI/src/SPI.cpp
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@ -124,12 +124,11 @@ uint16_t SPIClassRP2040::transfer16(uint16_t data) {
}
data = (_spis.getBitOrder() == MSBFIRST) ? data : reverse16Bit(data);
DEBUGSPI("SPI::transfer16(%04x), cpol=%d, cpha=%d\n", data, cpol(), cpha());
uint8_t msb, lsb;
msb = (data >> 8) & 0xff;
lsb = data & 0xff;
spi_write_read_blocking(_spi, &msb, &msb, 1);
spi_write_read_blocking(_spi, &lsb, &lsb, 1);
ret = ((msb << 8) | (lsb & 0xff)) & 0xffff;
uint8_t d[2];
d[0] = (data >> 8) & 0xff;
d[1] = data & 0xff;
spi_write_read_blocking(_spi, d, d, 2);
ret = ((d[0] << 8) | (d[1] & 0xff)) & 0xffff;
ret = (_spis.getBitOrder() == MSBFIRST) ? ret : reverse16Bit(ret);
DEBUGSPI("SPI: read back %02x\n", ret);
return ret;