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cpu/cc2538: spi: fix spi_transfer_bytes() with in_buf = NULL

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We have to read the DR for every byte that we write.
Just reading DR while SPI is busy in a loop can lead to bytes being
left in the fifo, corrupting subsequent reads.
This commit is contained in:
Benjamin Valentin 2020-03-09 16:22:37 +01:00
parent 5e9733645f
commit 68b2c57d2d
1 changed files with 1 additions and 3 deletions
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4
cpu/cc2538/periph/spi.c
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@ -139,9 +139,7 @@ void spi_transfer_bytes(spi_t bus, spi_cs_t cs, bool cont,
for (size_t i = 0; i < len; i++) {
while (!(dev(bus)->SR & SSI_SR_TNF)) {}
dev(bus)->DR = out_buf[i];
}
/* flush RX FIFO while busy*/
while ((dev(bus)->SR & SSI_SR_BSY)) {
while (!(dev(bus)->SR & SSI_SR_RNE)) {}
dev(bus)->DR;
}
}