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Bound STM32 SPI polling and report uncertain completion

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Signed-off-by: Rudy Celekli <47457359+rudycelekli@users.noreply.github.com>
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Rudy Celekli
2026-10-01 21:45:06 -04:00
parent d3f71c4bb8
commit f0bd561fad
1 changed files with 15 additions and 4 deletions
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engineering/engineering-embedded-firmware-engineer.md
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@@ -65,16 +65,27 @@ void app_main(void) {
```
### STM32 LL SPI Transfer (non-blocking)
### STM32 LL SPI Transfer (bounded polling, task context)
```c
void spi_write_byte(SPI_TypeDef *spi, uint8_t data) {
while (!LL_SPI_IsActiveFlag_TXE(spi));
// STM32 SPI with TXE/BSY flags (e.g. STM32F4); not an ISR-safe or non-blocking API.
// HAL_GetTick must advance while polling. One deadline covers both waits.
bool spi_write_byte(SPI_TypeDef *spi, uint8_t data, uint32_t timeout_ms) {
const uint32_t started = HAL_GetTick();
while (!LL_SPI_IsActiveFlag_TXE(spi)) {
if ((uint32_t)(HAL_GetTick() - started) >= timeout_ms) return false;
}
LL_SPI_TransmitData8(spi, data);
while (LL_SPI_IsActiveFlag_BSY(spi));
while (LL_SPI_IsActiveFlag_BSY(spi)) {
if ((uint32_t)(HAL_GetTick() - started) >= timeout_ms) return false;
}
return true;
}
```
A `false` result after the transmit write means completion is unknown: recover the
peripheral using the target MCU reference manual and errata before retrying; do not
blindly resend. Use interrupts or DMA when the caller must remain non-blocking.
### Nordic nRF BLE Advertisement (nRF Connect SDK / Zephyr)