static void spiStartTxn(spiStruct_t *interface) {
spiSlot_t *slot = &interface->slots[interface->tail];
spiClient_t *client = slot->client;
uint32_t tmp;
// is the current txn taking too long?
if (interface->txRunning != 0 && (timerMicros() - interface->txnStart) > SPI_MAX_TXN_TIME) {
spiDisableDMA(interface);
spiDisableSPI(interface);
spiDeselect(client);
interface->tail = (interface->tail + 1) % SPI_SLOTS;
slot = &interface->slots[interface->tail];
client = slot->client;
interface->txRunning = 0;
interface->txnTimeouts++;
}
if (interface->tail != interface->head && interface->txRunning == 0) {
interface->txRunning = 1;
interface->txnStart = timerMicros();
// set baud rate
tmp = interface->spi->CR1 & SPI_BAUD_MASK;
tmp |= client->baud;
interface->spi->CR1 = tmp;
// clear DR
SPI_I2S_ReceiveData(interface->spi);
spiSelect(client);
// specify "in transaction"
if (client->flag)
*client->flag = 0;
interface->rxDMAStream->M0AR = slot->rxBuf;
interface->rxDMAStream->NDTR = slot->size;
DMA_Cmd(interface->rxDMAStream, ENABLE);
interface->txDMAStream->M0AR = slot->txBuf;
interface->txDMAStream->NDTR = slot->size;
DMA_Cmd(interface->txDMAStream, ENABLE);
SPI_Cmd(interface->spi, ENABLE);
}
}
static void spiEndTxn(spiStruct_t *interface) {
uint8_t tail = interface->tail;
spiClient_t *client = interface->slots[tail].client;
uint32_t tmp;
spiDisableSPI(interface);
spiDisableDMA(interface);
spiDeselect(client);
// record longest txn
tmp = timerMicros() - interface->txnStart;
if (tmp > interface->txnMaxTime)
interface->txnMaxTime = tmp;
spiNotify(client);
tail = (tail + 1) % SPI_SLOTS;
interface->tail = tail;
interface->txRunning = 0;
spiTriggerSchedule(client->interface);
}
