DIY-Multiprotocol-TX-Module/BootLoaders/Boards/stm32/libraries/SPI/src/SPI.cpp

/******************************************************************************
 * The MIT License
 *
 * Copyright (c) 2010 Perry Hung.
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy,
 * modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *****************************************************************************/

/**
 * @author Marti Bolivar <mbolivar@leaflabs.com>
 * @brief Wirish SPI implementation.
 */

#include "SPI.h"


#include <libmaple/timer.h>
#include <libmaple/util.h>
#include <libmaple/rcc.h>

#include "wirish.h"
#include "boards.h"

//#include "HardwareSerial.h"
/** Time in ms for DMA receive timeout */
#define DMA_TIMEOUT 100

#if CYCLES_PER_MICROSECOND != 72
/* TODO [0.2.0?] something smarter than this */
#warning "Unexpected clock speed; SPI frequency calculation will be incorrect"
#endif

struct spi_pins {
    uint8 nss;
    uint8 sck;
    uint8 miso;
    uint8 mosi;
};

static const spi_pins* dev_to_spi_pins(spi_dev *dev);

static void configure_gpios(spi_dev *dev, bool as_master);

static spi_baud_rate determine_baud_rate(spi_dev *dev, uint32_t freq);

#if (BOARD_NR_SPI >= 3) && !defined(STM32_HIGH_DENSITY)
#error "The SPI library is misconfigured: 3 SPI ports only available on high density STM32 devices"
#endif

static const spi_pins board_spi_pins[] __FLASH__ = {
#if BOARD_NR_SPI >= 1
    {BOARD_SPI1_NSS_PIN,
     BOARD_SPI1_SCK_PIN,
     BOARD_SPI1_MISO_PIN,
     BOARD_SPI1_MOSI_PIN},
#endif
#if BOARD_NR_SPI >= 2
    {BOARD_SPI2_NSS_PIN,
     BOARD_SPI2_SCK_PIN,
     BOARD_SPI2_MISO_PIN,
     BOARD_SPI2_MOSI_PIN},
#endif
#if BOARD_NR_SPI >= 3
    {BOARD_SPI3_NSS_PIN,
     BOARD_SPI3_SCK_PIN,
     BOARD_SPI3_MISO_PIN,
     BOARD_SPI3_MOSI_PIN},
#endif
};


/*
 * Constructor
 */

SPIClass::SPIClass(uint32 spi_num)
{
    _currentSetting=&_settings[spi_num-1];// SPI channels are called 1 2 and 3 but the array is zero indexed

    switch (spi_num) {
#if BOARD_NR_SPI >= 1
    case 1:
        _currentSetting->spi_d = SPI1;
        _spi1_this = (void*) this;						  
        break;
#endif
#if BOARD_NR_SPI >= 2
    case 2:
        _currentSetting->spi_d = SPI2;
        _spi2_this = (void*) this;								  
        break;
#endif
#if BOARD_NR_SPI >= 3
    case 3:
        _currentSetting->spi_d = SPI3;
        _spi3_this = (void*) this;								  
        break;
#endif
    default:
        ASSERT(0);
    }

    // Init things specific to each SPI device
    // clock divider setup is a bit of hack, and needs to be improved at a later date.
    _settings[0].spi_d = SPI1;
    _settings[0].clockDivider = determine_baud_rate(_settings[0].spi_d, _settings[0].clock);
    _settings[0].spiDmaDev = DMA1;
    _settings[0].spiTxDmaChannel = DMA_CH3;
    _settings[0].spiRxDmaChannel = DMA_CH2;
    _settings[1].spi_d = SPI2;
    _settings[1].clockDivider = determine_baud_rate(_settings[1].spi_d, _settings[1].clock);
    _settings[1].spiDmaDev = DMA1;
    _settings[1].spiTxDmaChannel = DMA_CH5;
    _settings[1].spiRxDmaChannel = DMA_CH4;
#if BOARD_NR_SPI >= 3
    _settings[2].spi_d = SPI3;
    _settings[2].clockDivider = determine_baud_rate(_settings[2].spi_d, _settings[2].clock);
    _settings[2].spiDmaDev = DMA2;
    _settings[2].spiTxDmaChannel = DMA_CH2;
    _settings[2].spiRxDmaChannel = DMA_CH1;
#endif

    // added for DMA callbacks.
    _currentSetting->state = SPI_STATE_IDLE;
}

/*
 * Set up/tear down
 */
void SPIClass::updateSettings(void) {
    uint32 flags = ((_currentSetting->bitOrder == MSBFIRST ? SPI_FRAME_MSB : SPI_FRAME_LSB) | _currentSetting->dataSize | SPI_SW_SLAVE | SPI_SOFT_SS);
    spi_master_enable(_currentSetting->spi_d, (spi_baud_rate)_currentSetting->clockDivider, (spi_mode)_currentSetting->dataMode, flags);
}

void SPIClass::begin(void) {
    spi_init(_currentSetting->spi_d);
    configure_gpios(_currentSetting->spi_d, 1);
    updateSettings();
    // added for DMA callbacks.
    _currentSetting->state = SPI_STATE_READY;
}

void SPIClass::beginSlave(void) {
    spi_init(_currentSetting->spi_d);
    configure_gpios(_currentSetting->spi_d, 0);
    uint32 flags = ((_currentSetting->bitOrder == MSBFIRST ? SPI_FRAME_MSB : SPI_FRAME_LSB) | _currentSetting->dataSize | SPI_RX_ONLY);
    spi_slave_enable(_currentSetting->spi_d, (spi_mode)_currentSetting->dataMode, flags);
    // added for DMA callbacks.
    _currentSetting->state = SPI_STATE_READY;
}

void SPIClass::end(void) {
    if (!spi_is_enabled(_currentSetting->spi_d)) {
        return;
    }

    // Follows RM0008's sequence for disabling a SPI in master/slave
    // full duplex mode.
    while (spi_is_rx_nonempty(_currentSetting->spi_d)) {
        // FIXME [0.1.0] remove this once you have an interrupt based driver
        volatile uint16 rx __attribute__((unused)) = spi_rx_reg(_currentSetting->spi_d);
    }
    while (!spi_is_tx_empty(_currentSetting->spi_d))
        ;
    while (spi_is_busy(_currentSetting->spi_d))
        ;
    spi_peripheral_disable(_currentSetting->spi_d);
    // added for DMA callbacks.
    // Need to add unsetting the callbacks for the DMA channels.
    _currentSetting->state = SPI_STATE_IDLE;
}

/* Roger Clark added  3 functions */
void SPIClass::setClockDivider(uint32_t clockDivider)
{
    _currentSetting->clockDivider = clockDivider;
    uint32 cr1 = _currentSetting->spi_d->regs->CR1 & ~(SPI_CR1_BR);
    _currentSetting->spi_d->regs->CR1 = cr1 | (clockDivider & SPI_CR1_BR);
}

void SPIClass::setBitOrder(BitOrder bitOrder)
{
    _currentSetting->bitOrder = bitOrder;
    uint32 cr1 = _currentSetting->spi_d->regs->CR1 & ~(SPI_CR1_LSBFIRST);
    if ( bitOrder==LSBFIRST )	cr1 |= SPI_CR1_LSBFIRST;
    _currentSetting->spi_d->regs->CR1 = cr1;
}

/*	Victor Perez. Added to test changing datasize from 8 to 16 bit modes on the fly.
*	Input parameter should be SPI_CR1_DFF set to 0 or 1 on a 32bit word.
*	
*/
void SPIClass::setDataSize(uint32 datasize)
{
    _currentSetting->dataSize = datasize;
    uint32 cr1 = _currentSetting->spi_d->regs->CR1 & ~(SPI_CR1_DFF);
    uint8 en = spi_is_enabled(_currentSetting->spi_d);
    spi_peripheral_disable(_currentSetting->spi_d);
    _currentSetting->spi_d->regs->CR1 = cr1 | (datasize & SPI_CR1_DFF) | en;
}

void SPIClass::setDataMode(uint8_t dataMode)
{
/* Notes.  As far as I can tell, the AVR numbers for dataMode appear to match the numbers required by the STM32

From the AVR doc http://www.atmel.com/images/doc2585.pdf section 2.4

SPI Mode 	CPOL 	CPHA 	Shift SCK-edge 	Capture SCK-edge
0 			0 		0 		Falling 		Rising
1 			0 		1 		Rising 			Falling
2 			1 		0 		Rising 			Falling
3 			1 		1 		Falling 		Rising
 
 
On the STM32 it appears to be

bit 1 - CPOL : Clock polarity
    (This bit should not be changed when communication is ongoing)
    0 : CLK to 0 when idle
    1 : CLK to 1 when idle
 
bit 0 - CPHA : Clock phase
    (This bit should not be changed when communication is ongoing)
    0 : The first clock transition is the first data capture edge
    1 : The second clock transition is the first data capture edge
 
If someone finds this is not the case or sees a logic error with this let me know ;-) 
 */
    _currentSetting->dataMode = dataMode;
    uint32 cr1 = _currentSetting->spi_d->regs->CR1 & ~(SPI_CR1_CPOL|SPI_CR1_CPHA);
    _currentSetting->spi_d->regs->CR1 = cr1 | (dataMode & (SPI_CR1_CPOL|SPI_CR1_CPHA));
}

void SPIClass::beginTransaction(uint8_t pin, SPISettings settings)
{
    setBitOrder(settings.bitOrder);
    setDataMode(settings.dataMode);
    setDataSize(settings.dataSize);
    setClockDivider(determine_baud_rate(_currentSetting->spi_d, settings.clock));
    begin();
}

void SPIClass::beginTransactionSlave(SPISettings settings)
{
    setBitOrder(settings.bitOrder);
    setDataMode(settings.dataMode);
    setDataSize(settings.dataSize);
    beginSlave();
}

void SPIClass::endTransaction(void)
{
    //digitalWrite(_SSPin,HIGH);
#if false
// code from SAM core
    uint8_t mode = interruptMode;
    if (mode > 0) {
        if (mode < 16) {
            if (mode & 1) PIOA->PIO_IER = interruptMask[0];
            if (mode & 2) PIOB->PIO_IER = interruptMask[1];
            if (mode & 4) PIOC->PIO_IER = interruptMask[2];
            if (mode & 8) PIOD->PIO_IER = interruptMask[3];
        } else {
            if (interruptSave) interrupts();
        }
    }
#endif
}


/*
 * I/O
 */

uint16 SPIClass::read(void)
{
    while ( spi_is_rx_nonempty(_currentSetting->spi_d)==0 ) ;
    return (uint16)spi_rx_reg(_currentSetting->spi_d);
}

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;
    // 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
}

void SPIClass::write(uint16 data)
{
    /* Added for 16bit data Victor Perez. Roger Clark 
     * Improved speed by just directly writing the single byte to the SPI data reg and wait for completion,
     * by taking the Tx code from transfer(byte)
     * 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)
    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." 
}

void SPIClass::write16(uint16 data)
{
    // Added by stevestrong: write two consecutive bytes in 8 bit mode (DFF=0)
    spi_tx_reg(_currentSetting->spi_d, data>>8); // write high byte
    while (spi_is_tx_empty(_currentSetting->spi_d) == 0); // Wait until TXE=1
    spi_tx_reg(_currentSetting->spi_d, data); // write low byte
    while (spi_is_tx_empty(_currentSetting->spi_d) == 0); // Wait until TXE=1
    while (spi_is_busy(_currentSetting->spi_d) != 0); // wait until BSY=0
}

void SPIClass::write(uint16 data, uint32 n)
{
    // Added by stevstrong: Repeatedly send same data by the specified number of times
    spi_reg_map * regs = _currentSetting->spi_d->regs;
    while ( (n--)>0 ) {
        regs->DR = data; // write the data to be transmitted into the SPI_DR register (this clears the TXE flag)
        while ( (regs->SR & SPI_SR_TXE)==0 ) ; // wait till Tx empty
    }
    while ( (regs->SR & SPI_SR_BSY) != 0); // wait until BSY=0 before returning 
}

void SPIClass::write(const void *data, uint32 length)
{
    spi_dev * spi_d = _currentSetting->spi_d;
    spi_tx(spi_d, data, length); // data can be array of bytes or words
    while (spi_is_tx_empty(spi_d) == 0); // "5. Wait until TXE=1 ..."
    while (spi_is_busy(spi_d) != 0); // "... and then wait until BSY=0 before disabling the SPI."
}

uint8 SPIClass::transfer(uint8 byte) const
{
    spi_dev * spi_d = _currentSetting->spi_d;
    spi_rx_reg(spi_d); // read any previous data
    spi_tx_reg(spi_d, byte); // Write the data item to be transmitted into the SPI_DR register
    while (spi_is_tx_empty(spi_d) == 0); // "5. Wait until TXE=1 ..."
    while (spi_is_busy(spi_d) != 0); // "... and then wait until BSY=0 before disabling the SPI."
    return (uint8)spi_rx_reg(spi_d); // "... and read the last received data."
}

uint16_t SPIClass::transfer16(uint16_t data) const
{
    // Modified by stevestrong: write & read two consecutive bytes in 8 bit mode (DFF=0)
	// This is more effective than two distinct byte transfers
    spi_dev * spi_d = _currentSetting->spi_d;
    spi_rx_reg(spi_d);                   // read any previous data
    spi_tx_reg(spi_d, data>>8);          // write high byte
    while (spi_is_tx_empty(spi_d) == 0); // wait until TXE=1
    while (spi_is_busy(spi_d) != 0);     // wait until BSY=0
	uint16_t ret = spi_rx_reg(spi_d)<<8; // read and shift high byte
    spi_tx_reg(spi_d, data);             // write low byte
    while (spi_is_tx_empty(spi_d) == 0); // wait until TXE=1
    while (spi_is_busy(spi_d) != 0);     // wait until BSY=0
	ret += spi_rx_reg(spi_d);            // read low byte
    return ret;
}

/*  Roger Clark and Victor Perez, 2015
*	Performs a DMA SPI transfer with at least a receive buffer.
*	If a TX buffer is not provided, FF is sent over and over for the lenght of the transfer. 
*	On exit TX buffer is not modified, and RX buffer cotains the received data.
*	Still in progress.
*/
void SPIClass::dmaTransferSet(const void *transmitBuf, void *receiveBuf) {
    dma_init(_currentSetting->spiDmaDev);
    //spi_rx_dma_enable(_currentSetting->spi_d);
    //spi_tx_dma_enable(_currentSetting->spi_d);
    dma_xfer_size dma_bit_size = (_currentSetting->dataSize==DATA_SIZE_16BIT) ? DMA_SIZE_16BITS : DMA_SIZE_8BITS;
    dma_setup_transfer(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel, &_currentSetting->spi_d->regs->DR, dma_bit_size,
                     receiveBuf, dma_bit_size, (DMA_MINC_MODE | DMA_TRNS_CMPLT ));// receive buffer DMA
    if (!transmitBuf) {
    transmitBuf = &ff;
    dma_setup_transfer(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, &_currentSetting->spi_d->regs->DR, dma_bit_size,
                       (volatile void*)transmitBuf, dma_bit_size, (DMA_FROM_MEM));// Transmit FF repeatedly
    }
    else {
    dma_setup_transfer(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, &_currentSetting->spi_d->regs->DR, dma_bit_size,
                       (volatile void*)transmitBuf, dma_bit_size, (DMA_MINC_MODE |  DMA_FROM_MEM ));// Transmit buffer DMA
    }
    dma_set_priority(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, DMA_PRIORITY_LOW);
    dma_set_priority(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel, DMA_PRIORITY_VERY_HIGH);
}

uint8 SPIClass::dmaTransferRepeat(uint16 length) {
    if (length == 0) return 0;
    if (spi_is_rx_nonempty(_currentSetting->spi_d) == 1) spi_rx_reg(_currentSetting->spi_d);
    _currentSetting->state = SPI_STATE_TRANSFER;
    dma_set_num_transfers(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel, length);
    dma_set_num_transfers(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, length);
    dma_enable(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel);// enable receive
    dma_enable(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);// enable transmit
    spi_rx_dma_enable(_currentSetting->spi_d);
    spi_tx_dma_enable(_currentSetting->spi_d);
    if (_currentSetting->receiveCallback){
        return 0;
    }
    //uint32_t m = millis();
    uint8 b = 0;
    uint32_t m = millis();
    while ((dma_get_isr_bits(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel) & DMA_ISR_TCIF1)==0) {
        //Avoid interrupts and just loop waiting for the flag to be set.
        if ((millis() - m) > DMA_TIMEOUT) { b = 2; break; }
    }

    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."
    spi_tx_dma_disable(_currentSetting->spi_d);
    spi_rx_dma_disable(_currentSetting->spi_d);
    dma_disable(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);
    dma_disable(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel);
    dma_clear_isr_bits(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel);
    dma_clear_isr_bits(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);
    _currentSetting->state = SPI_STATE_READY;
    return b;
}

/*  Roger Clark and Victor Perez, 2015
*	Performs a DMA SPI transfer with at least a receive buffer.
*	If a TX buffer is not provided, FF is sent over and over for the length of the transfer. 
*	On exit TX buffer is not modified, and RX buffer contains the received data.
*	Still in progress.
*/

uint8 SPIClass::dmaTransfer(const void *transmitBuf, void *receiveBuf, uint16 length) {
    dmaTransferSet(transmitBuf, receiveBuf);
    return dmaTransferRepeat(length);
}

/*  Roger Clark and Victor Perez, 2015
*	Performs a DMA SPI send using a TX buffer.
*	On exit TX buffer is not modified.
*	Still in progress.
*	2016 - stevstrong - reworked to automatically detect bit size from SPI setting
*/

void SPIClass::dmaSendSet(const void * transmitBuf, bool minc) {
   uint32 flags = ( (DMA_MINC_MODE*minc) | DMA_FROM_MEM | DMA_TRNS_CMPLT);
   dma_init(_currentSetting->spiDmaDev);
   dma_xfer_size dma_bit_size = (_currentSetting->dataSize==DATA_SIZE_16BIT) ? DMA_SIZE_16BITS : DMA_SIZE_8BITS;
   dma_setup_transfer(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, &_currentSetting->spi_d->regs->DR, dma_bit_size,
                       (volatile void*)transmitBuf, dma_bit_size, flags);// Transmit buffer DMA
   dma_set_priority(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, DMA_PRIORITY_LOW);
}

uint8 SPIClass::dmaSendRepeat(uint16 length) {
    if (length == 0) return 0;
    dma_clear_isr_bits(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);
    dma_set_num_transfers(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, length);
    _currentSetting->state = SPI_STATE_TRANSMIT;
    dma_enable(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);// enable transmit
    spi_tx_dma_enable(_currentSetting->spi_d);				  
    if (_currentSetting->transmitCallback)
    {
        return 0;
    }
    uint32_t m = millis();
    uint8 b = 0;
    while ((dma_get_isr_bits(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel) & DMA_ISR_TCIF1)==0) {
        //Avoid interrupts and just loop waiting for the flag to be set.
        if ((millis() - m) > DMA_TIMEOUT) { b = 2; break; }
    }
    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." 
    spi_tx_dma_disable(_currentSetting->spi_d);
    dma_disable(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);
    dma_clear_isr_bits(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);
    _currentSetting->state = SPI_STATE_READY;
    return b;
}

uint8 SPIClass::dmaSend(const void * transmitBuf, uint16 length, bool minc) {
    dmaSendSet(transmitBuf, minc);
    return dmaSendRepeat(length);
}

uint8 SPIClass::dmaSendAsync(const void * transmitBuf, uint16 length, bool minc) {
    uint8 b = 0;	

    if (_currentSetting->state != SPI_STATE_READY)
    {

        uint32_t m = millis();
        while ((dma_get_isr_bits(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel) & DMA_ISR_TCIF1)==0) {//Avoid interrupts and just loop waiting for the flag to be set.
            //delayMicroseconds(10);
            if ((millis() - m) > DMA_TIMEOUT) { b = 2; break; }
        }		

        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." 
        spi_tx_dma_disable(_currentSetting->spi_d);
        dma_disable(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);
        _currentSetting->state = SPI_STATE_READY;
    }

    if (length == 0) return 0;
    uint32 flags = ( (DMA_MINC_MODE*minc) | DMA_FROM_MEM | DMA_TRNS_CMPLT);

    dma_init(_currentSetting->spiDmaDev);
    // TX
    dma_xfer_size dma_bit_size = (_currentSetting->dataSize==DATA_SIZE_16BIT) ? DMA_SIZE_16BITS : DMA_SIZE_8BITS;
    dma_setup_transfer(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, &_currentSetting->spi_d->regs->DR, dma_bit_size,
    (volatile void*)transmitBuf, dma_bit_size, flags);// Transmit buffer DMA 
    dma_set_num_transfers(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, length);
    dma_clear_isr_bits(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);
    dma_enable(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);// enable transmit
    spi_tx_dma_enable(_currentSetting->spi_d);	

    _currentSetting->state = SPI_STATE_TRANSMIT;

    return b;
}


/*
    New functions added to manage callbacks.
    Victor Perez 2017
*/

void SPIClass::onReceive(void(*callback)(void)) {
    _currentSetting->receiveCallback = callback;
    if (callback){
        switch (_currentSetting->spi_d->clk_id) {
        case RCC_SPI1:
            dma_attach_interrupt(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel, &SPIClass::_spi1EventCallback);
            break;
        case RCC_SPI2:
            dma_attach_interrupt(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel, &SPIClass::_spi2EventCallback);
            break;
            #if BOARD_NR_SPI >= 3
        case RCC_SPI3:
            dma_attach_interrupt(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel, &SPIClass::_spi3EventCallback);
            break;
            #endif
        default:
            ASSERT(0);
        }
    }
    else {
        dma_detach_interrupt(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel);
    }
}

void SPIClass::onTransmit(void(*callback)(void)) {
    _currentSetting->transmitCallback = callback;
    if (callback){
        switch (_currentSetting->spi_d->clk_id) {
        case RCC_SPI1:
            dma_attach_interrupt(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, &SPIClass::_spi1EventCallback);
            break;
        case RCC_SPI2:
            dma_attach_interrupt(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, &SPIClass::_spi2EventCallback);
            break;
            #if BOARD_NR_SPI >= 3
        case RCC_SPI3:
            dma_attach_interrupt(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel, &SPIClass::_spi3EventCallback);
            break;
            #endif
        default:
            ASSERT(0);
        }
    }
    else {
        dma_detach_interrupt(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);
    }
}

/*
    TODO: check if better to first call the customer code, next disable the DMA requests.
    Also see if we need to check whether callbacks are set or not, may be better to be checked during the initial setup and only set the callback to EventCallback if they are set.
*/

void SPIClass::EventCallback() {
    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"
    switch (_currentSetting->state) {
    case SPI_STATE_TRANSFER:
        while (spi_is_rx_nonempty(_currentSetting->spi_d));
        _currentSetting->state = SPI_STATE_READY;
        spi_tx_dma_disable(_currentSetting->spi_d);
        spi_rx_dma_disable(_currentSetting->spi_d);
        //dma_disable(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);
        //dma_disable(_currentSetting->spiDmaDev, _currentSetting->spiRxDmaChannel);

        if (_currentSetting->receiveCallback)
        {
            _currentSetting->receiveCallback();
        }
        break;
    case SPI_STATE_TRANSMIT:
        _currentSetting->state = SPI_STATE_READY;
        spi_tx_dma_disable(_currentSetting->spi_d);
        //dma_disable(_currentSetting->spiDmaDev, _currentSetting->spiTxDmaChannel);
        if (_currentSetting->transmitCallback)
        {
            _currentSetting->transmitCallback();
        }

        break;
    default:
        // we shouldn't get here, so better to add an assert and fail.
        return;
    }
}

void SPIClass::attachInterrupt(void) {
    // Should be enableInterrupt()
}

void SPIClass::detachInterrupt(void) {
    // Should be disableInterrupt()
}

/*
 * Pin accessors
 */

uint8 SPIClass::misoPin(void) {
    return dev_to_spi_pins(_currentSetting->spi_d)->miso;
}

uint8 SPIClass::mosiPin(void) {
    return dev_to_spi_pins(_currentSetting->spi_d)->mosi;
}

uint8 SPIClass::sckPin(void) {
    return dev_to_spi_pins(_currentSetting->spi_d)->sck;
}

uint8 SPIClass::nssPin(void) {
    return dev_to_spi_pins(_currentSetting->spi_d)->nss;
}

/*
 * Deprecated functions
 */

uint8 SPIClass::send(uint8 data) {
    this->write(data);
    return 1;
}

uint8 SPIClass::send(uint8 *buf, uint32 len) {
    this->write(buf, len);
    return len;
}

uint8 SPIClass::recv(void) {
    return this->read();
}

/*
    DMA call back functions, one per port.
*/

void SPIClass::_spi1EventCallback()
{
    reinterpret_cast<class SPIClass*>(_spi1_this)->EventCallback();
}

void SPIClass::_spi2EventCallback() {
    reinterpret_cast<class SPIClass*>(_spi2_this)->EventCallback();
}
#if BOARD_NR_SPI >= 3
void SPIClass::_spi3EventCallback() {
    reinterpret_cast<class SPIClass*>(_spi3_this)->EventCallback();
}
#endif
/*
* Auxiliary functions
*/

static const spi_pins* dev_to_spi_pins(spi_dev *dev) {
    switch (dev->clk_id) {
#if BOARD_NR_SPI >= 1
    case RCC_SPI1: return board_spi_pins;
#endif
#if BOARD_NR_SPI >= 2
    case RCC_SPI2: return board_spi_pins + 1;
#endif
#if BOARD_NR_SPI >= 3
    case RCC_SPI3: return board_spi_pins + 2;
#endif
    default:       return NULL;
    }
}

static void disable_pwm(const stm32_pin_info *i) {
    if (i->timer_device) {
        timer_set_mode(i->timer_device, i->timer_channel, TIMER_DISABLED);
    }
}

static void configure_gpios(spi_dev *dev, bool as_master) {
    const spi_pins *pins = dev_to_spi_pins(dev);

    if (!pins) {
        return;
    }

    const stm32_pin_info *nssi = &PIN_MAP[pins->nss];
    const stm32_pin_info *scki = &PIN_MAP[pins->sck];
    const stm32_pin_info *misoi = &PIN_MAP[pins->miso];
    const stm32_pin_info *mosii = &PIN_MAP[pins->mosi];

    disable_pwm(nssi);
    disable_pwm(scki);
    disable_pwm(misoi);
    disable_pwm(mosii);

    spi_config_gpios(dev, as_master, nssi->gpio_device, nssi->gpio_bit,
    scki->gpio_device, scki->gpio_bit, misoi->gpio_bit,
    mosii->gpio_bit);
}

static const spi_baud_rate baud_rates[8] __FLASH__ = {
    SPI_BAUD_PCLK_DIV_2,
    SPI_BAUD_PCLK_DIV_4,
    SPI_BAUD_PCLK_DIV_8,
    SPI_BAUD_PCLK_DIV_16,
    SPI_BAUD_PCLK_DIV_32,
    SPI_BAUD_PCLK_DIV_64,
    SPI_BAUD_PCLK_DIV_128,
    SPI_BAUD_PCLK_DIV_256,
};

/*
* Note: This assumes you're on a LeafLabs-style board
* (CYCLES_PER_MICROSECOND == 72, APB2 at 72MHz, APB1 at 36MHz).
*/
static spi_baud_rate determine_baud_rate(spi_dev *dev, uint32_t freq) {
    uint32_t clock = 0, i;
    switch (rcc_dev_clk(dev->clk_id))
    {
    case RCC_APB2: clock = STM32_PCLK2; break; // 72 Mhz
    case RCC_APB1: clock = STM32_PCLK1; break; // 36 Mhz
    }
    clock /= 2;
    i = 0;
    while (i < 7 && freq < clock) {
        clock /= 2;
        i++;
    }
    return baud_rates[i];
}

SPIClass SPI(1);