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I have a PIC18F27K40 and would like to use the hardware SPI module. Of course, it would not take too much code to write a SPI library myself, but if it exists already I prefer to not reinvent the wheel.

Before, I always used the legacy peripheral libraries (plib), but they haven't been updated for a long time, and pconfig.h does not contain the required #defines for my chip.

Is then the only way now to use the MPLAB Code Configurator? I don't have MPLAB installed and it seems a large overhead if it's only to generate some peripheral libraries. Is there no other way?

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  • \$\begingroup\$ MCC hardly generates much code for SPI, less than 100 lines in total if you remove the comments. If you tell me what config you want and which MSSP module, I can generate the code and either post as an answer or email to you but it's probably just as easy to write a few functions yourself. \$\endgroup\$ – Roger Rowland Jan 28 '17 at 10:35
  • \$\begingroup\$ @RogerRowland that would be great. I think it's good as an answer, I doubt it will be very specific to this processor (so then others may also use it). And so you don't know about other ways to get a library for the newer chips? \$\endgroup\$ – user17592 Jan 28 '17 at 10:37
  • \$\begingroup\$ Well, it's not really a library as such, just a handful of functions. What would you like generated? MSSP1 or MSSP2? SPI mode? Speed? Or does it matter? You can change anything easily afterwards. MCC generates code specific to your needs, it's not a generic library. \$\endgroup\$ – Roger Rowland Jan 28 '17 at 10:40
  • \$\begingroup\$ @RogerRowland doesn't matter much, but let's do MSSP1, master mode 0,0, SMPMID, 1MHz (at a 64MHz FOsc). Thanks a lot! \$\endgroup\$ – user17592 Jan 28 '17 at 10:43
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Example generated code follows, as you requested, for MSSP1, master mode 0,0, SMPMID, 1MHz (at a 64MHz FOsc). First for file "spi1.h":

/**
  MSSP1 Generated Driver API Header File

  @Company
    Microchip Technology Inc.

  @File Name
    mssp1.h

  @Summary
    This is the generated header file for the MSSP1 driver using MPLAB(c) Code Configurator

  @Description
    This header file provides APIs for MSSP1.
    Generation Information :
        Product Revision  :  MPLAB(c) Code Configurator - 4.15
        Device            :  PIC18F27K40
        Driver Version    :  2.00
    The generated drivers are tested against the following:
        Compiler          :  XC8 1.35
        MPLAB             :  MPLAB X 3.40
*******************************************************************************/

/*
    (c) 2016 Microchip Technology Inc. and its subsidiaries. You may use this
    software and any derivatives exclusively with Microchip products.

    THIS SOFTWARE IS SUPPLIED BY MICROCHIP "AS IS". NO WARRANTIES, WHETHER
    EXPRESS, IMPLIED OR STATUTORY, APPLY TO THIS SOFTWARE, INCLUDING ANY IMPLIED
    WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY, AND FITNESS FOR A
    PARTICULAR PURPOSE, OR ITS INTERACTION WITH MICROCHIP PRODUCTS, COMBINATION
    WITH ANY OTHER PRODUCTS, OR USE IN ANY APPLICATION.

    IN NO EVENT WILL MICROCHIP BE LIABLE FOR ANY INDIRECT, SPECIAL, PUNITIVE,
    INCIDENTAL OR CONSEQUENTIAL LOSS, DAMAGE, COST OR EXPENSE OF ANY KIND
    WHATSOEVER RELATED TO THE SOFTWARE, HOWEVER CAUSED, EVEN IF MICROCHIP HAS
    BEEN ADVISED OF THE POSSIBILITY OR THE DAMAGES ARE FORESEEABLE. TO THE
    FULLEST EXTENT ALLOWED BY LAW, MICROCHIP'S TOTAL LIABILITY ON ALL CLAIMS IN
    ANY WAY RELATED TO THIS SOFTWARE WILL NOT EXCEED THE AMOUNT OF FEES, IF ANY,
    THAT YOU HAVE PAID DIRECTLY TO MICROCHIP FOR THIS SOFTWARE.

    MICROCHIP PROVIDES THIS SOFTWARE CONDITIONALLY UPON YOUR ACCEPTANCE OF THESE
    TERMS.
*/

#ifndef _SPI1_H
#define _SPI1_H

/**
  Section: Included Files
*/

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

#ifdef __cplusplus  // Provide C++ Compatibility

    extern "C" {

#endif

/**
  Section: Macro Declarations
*/

#define DUMMY_DATA 0x0

/**
  Section: SPI1 Module APIs
*/

/**
  @Summary
    Initializes the SPI1

  @Description
    This routine initializes the SPI1.
    This routine must be called before any other MSSP1 routine is called.
    This routine should only be called once during system initialization.

  @Preconditions
    None

  @Param
    None

  @Returns
    None

  @Comment


  @Example
    <code>
    uint8_t     myWriteBuffer[MY_BUFFER_SIZE];
    uint8_t     myReadBuffer[MY_BUFFER_SIZE];
    uint8_t     writeData;
    uint8_t     readData;
    uint8_t     total;

    SPI1_Initialize();

    total = 0;
    do
    {
        total = SPI1_Exchange8bitBuffer(&myWriteBuffer[total], MY_BUFFER_SIZE - total, &myWriteBuffer[total]);

        // Do something else...

    } while(total < MY_BUFFER_SIZE);

    readData = SPI1_Exchange8bit(writeData);
    </code>
 */
void SPI1_Initialize(void);

/**
  @Summary
    Exchanges a data byte over SPI1

  @Description
    This routine exchanges a data byte over SPI1 bus.
    This is a blocking routine.

  @Preconditions
    The SPI1_Initialize() routine should be called
    prior to use this routine.

  @Param
    data - data byte to be transmitted over SPI1 bus

  @Returns
    The received byte over SPI1 bus

  @Example
    <code>
    uint8_t     writeData;
    uint8_t     readData;
    uint8_t     readDummy;

    SPI1_Initialize();

    // for transmission over SPI bus
    readDummy = SPI1_Exchange8bit(writeData);

    // for reception over SPI bus
    readData = SPI1_Exchange8bit(DUMMY_DATA);
    </code>
 */
uint8_t SPI1_Exchange8bit(uint8_t data);

 /**
  @Summary
    Exchanges buffer of data over SPI1

  @Description
    This routine exchanges buffer of data (of size one byte) over SPI1 bus.
    This is a blocking routine.

  @Preconditions
    The SPI1_Initialize() routine should be called
    prior to use this routine.

  @Param
    dataIn  - Buffer of data to be transmitted over SPI1.
    bufLen  - Number of bytes to be exchanged.
    dataOut - Buffer of data to be received over SPI1.

  @Returns
    Number of bytes exchanged over SPI1.

  @Example
    <code>
    uint8_t     myWriteBuffer[MY_BUFFER_SIZE];
    uint8_t     myReadBuffer[MY_BUFFER_SIZE];
    uint8_t     total;

    SPI1_Initialize();

    total = 0;
    do
    {
        total = SPI1_Exchange8bitBuffer(&myWriteBuffer[total], MY_BUFFER_SIZE - total, &myWriteBuffer[total]);

        // Do something else...

    } while(total < MY_BUFFER_SIZE);
    </code>
 */
uint8_t SPI1_Exchange8bitBuffer(uint8_t *dataIn, uint8_t bufLen, uint8_t *dataOut);

/**
  @Summary
    Gets the SPI1 buffer full status

  @Description
    This routine gets the SPI1 buffer full status

  @Preconditions
    The SPI1_Initialize() routine should be called
    prior to use this routine.

  @Param
    None

  @Returns
    true  - if the buffer is full
    false - if the buffer is not full.

  @Example
    Refer to SPI1_Initialize() for an example
 */
bool SPI1_IsBufferFull(void);

/**
  @Summary
    Gets the status of write collision.

  @Description
    This routine gets the status of write collision.

  @Preconditions
    The SPI1_Initialize() routine must have been called prior to use this routine.

  @Param
    None

  @Returns
    true  - if the write collision has occurred.
    false - if the write collision has not occurred.

  @Example
    if(SPI1_HasWriteCollisionOccured())
    {
        SPI1_ClearWriteCollisionStatus();
    }
*/
bool SPI1_HasWriteCollisionOccured(void);

/**
  @Summary
    Clears the status of write collision.

  @Description
    This routine clears the status of write collision.

  @Preconditions
    The SPI1_Initialize() routine must have been called prior to use this routine.

  @Param
    None

  @Returns
    None

  @Example
    if(SPI1_HasWriteCollisionOccured())
    {
        SPI1_ClearWriteCollisionStatus();
    }
*/
void SPI1_ClearWriteCollisionStatus(void);

#ifdef __cplusplus  // Provide C++ Compatibility

    }

#endif

#endif // _SPI1_H

Now, for file "spi1.c":

/**
  MSSP1 Generated Driver File

  @Company
    Microchip Technology Inc.

  @File Name
    spi1.c

  @Summary
    This is the generated driver implementation file for the MSSP1 driver using MPLAB(c) Code Configurator

  @Description
    This source file provides APIs for MSSP1.
    Generation Information :
        Product Revision  :  MPLAB(c) Code Configurator - 4.15
        Device            :  PIC18F27K40
        Driver Version    :  2.00
    The generated drivers are tested against the following:
        Compiler          :  XC8 1.35
        MPLAB             :  MPLAB X 3.40
*/

/*
    (c) 2016 Microchip Technology Inc. and its subsidiaries. You may use this
    software and any derivatives exclusively with Microchip products.

    THIS SOFTWARE IS SUPPLIED BY MICROCHIP "AS IS". NO WARRANTIES, WHETHER
    EXPRESS, IMPLIED OR STATUTORY, APPLY TO THIS SOFTWARE, INCLUDING ANY IMPLIED
    WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY, AND FITNESS FOR A
    PARTICULAR PURPOSE, OR ITS INTERACTION WITH MICROCHIP PRODUCTS, COMBINATION
    WITH ANY OTHER PRODUCTS, OR USE IN ANY APPLICATION.

    IN NO EVENT WILL MICROCHIP BE LIABLE FOR ANY INDIRECT, SPECIAL, PUNITIVE,
    INCIDENTAL OR CONSEQUENTIAL LOSS, DAMAGE, COST OR EXPENSE OF ANY KIND
    WHATSOEVER RELATED TO THE SOFTWARE, HOWEVER CAUSED, EVEN IF MICROCHIP HAS
    BEEN ADVISED OF THE POSSIBILITY OR THE DAMAGES ARE FORESEEABLE. TO THE
    FULLEST EXTENT ALLOWED BY LAW, MICROCHIP'S TOTAL LIABILITY ON ALL CLAIMS IN
    ANY WAY RELATED TO THIS SOFTWARE WILL NOT EXCEED THE AMOUNT OF FEES, IF ANY,
    THAT YOU HAVE PAID DIRECTLY TO MICROCHIP FOR THIS SOFTWARE.

    MICROCHIP PROVIDES THIS SOFTWARE CONDITIONALLY UPON YOUR ACCEPTANCE OF THESE
    TERMS.
*/

/**
  Section: Included Files
*/

#include <xc.h>
#include "spi1.h"

/**
  Section: Macro Declarations
*/

#define SPI_RX_IN_PROGRESS 0x0

/**
  Section: Module APIs
*/

void SPI1_Initialize(void)
{
    // Set the SPI1 module to the options selected in the User Interface

    // SMP Middle; CKE Active to Idle; 
    SSP1STAT = 0x40;

    // SSPEN enabled; CKP Idle:Low, Active:High; SSPM FOSC/64; 
    SSP1CON1 = 0x22;

    // SSPADD 0; 
    SSP1ADD = 0x00;
}

uint8_t SPI1_Exchange8bit(uint8_t data)
{
    // Clear the Write Collision flag, to allow writing
    SSP1CON1bits.WCOL = 0;

    SSP1BUF = data;

    while(SSP1STATbits.BF == SPI_RX_IN_PROGRESS)
    {
    }

    return (SSP1BUF);
}

uint8_t SPI1_Exchange8bitBuffer(uint8_t *dataIn, uint8_t bufLen, uint8_t *dataOut)
{
    uint8_t bytesWritten = 0;

    if(bufLen != 0)
    {
        if(dataIn != NULL)
        {
            while(bytesWritten < bufLen)
            {
                if(dataOut == NULL)
                {
                    SPI1_Exchange8bit(dataIn[bytesWritten]);
                }
                else
                {
                    dataOut[bytesWritten] = SPI1_Exchange8bit(dataIn[bytesWritten]);
                }

                bytesWritten++;
            }
        }
        else
        {
            if(dataOut != NULL)
            {
                while(bytesWritten < bufLen )
                {
                    dataOut[bytesWritten] = SPI1_Exchange8bit(DUMMY_DATA);

                    bytesWritten++;
                }
            }
        }
    }

    return bytesWritten;
}

bool SPI1_IsBufferFull(void)
{
    return (SSP1STATbits.BF);
}

bool SPI1_HasWriteCollisionOccured(void)
{
    return (SSP1CON1bits.WCOL);
}

void SPI1_ClearWriteCollisionStatus(void)
{
    SSP1CON1bits.WCOL = 0;
}
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