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improved block read routine

This commit is contained in:
stevstrong 2017-05-09 17:00:27 +02:00 committed by GitHub
parent e37d7eac48
commit 59b71f1370
1 changed files with 20 additions and 3 deletions
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19
STM32F4/libraries/SPI/src/SPI.cpp
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@ -321,14 +321,32 @@ uint16 SPIClass::read(void)
void SPIClass::read(uint8 *buf, uint32 len)
{
if ( len == 0 ) return;
spi_rx_reg(_currentSetting->spi_d); // clear the RX buffer in case a byte is waiting on it.
spi_reg_map * regs = _currentSetting->spi_d->regs;
#if 1
// start sequence: write byte 0
regs->DR = 0x00FF; // write the first byte
// main loop
while ( (--len) ) {
while( !(regs->SR & SPI_SR_TXE) ); // wait for TXE flag
noInterrupts(); // go atomic level - avoid interrupts to surely get the previously received data
regs->DR = 0x00FF; // write the next data item to be transmitted into the SPI_DR register. This clears the TXE flag.
while ( !(regs->SR & SPI_SR_RXNE) ); // wait till data is available in the DR register
*buf++ = (uint8)(regs->DR); // read and store the received byte. This clears the RXNE flag.
interrupts(); // let systick do its job
}
// read remaining last byte
while ( !(regs->SR & SPI_SR_RXNE) ); // wait till data is available in the Rx register
*buf++ = (uint8)(regs->DR); // read and store the received byte
#else
// start sequence
while ( (len--)>0) {
regs->DR = 0x00FF; // " write the data item to be transmitted into the SPI_DR register (this clears the TXE flag)."
while ( (regs->SR & SPI_SR_RXNE)==0 ) ; // wait till data is available in the Rx register
*buf++ = (uint8)(regs->DR); // read and store the received byte
}
#endif
}
void SPIClass::write(uint16 data)
@ -339,7 +357,6 @@ void SPIClass::write(uint16 data)
* This almost doubles the speed of this function.
*/
spi_tx_reg(_currentSetting->spi_d, data); // write the data to be transmitted into the SPI_DR register (this clears the TXE flag)
//return;
while (spi_is_tx_empty(_currentSetting->spi_d) == 0); // "5. Wait until TXE=1 ..."
while (spi_is_busy(_currentSetting->spi_d) != 0); // "... and then wait until BSY=0 before disabling the SPI."
}