mcp41xxx_spi_pot.c - SPI example: PIC24 uC in Master mode to Microchip MCP41xxx Digital Potentiometer

 
#include "pic24_all.h"
#include <stdio.h>

#define CONFIG_SLAVE_ENABLE() CONFIG_RB2_AS_DIG_OUTPUT()
#define SLAVE_ENABLE()        _LATB2 = 0  //low true assertion
#define SLAVE_DISABLE()       _LATB2 = 1


void configSPI1(void) {
  SPI1CON1 =
#if (defined(__dsPIC33E__) || defined(__PIC24E__))
    //spi clock = 60MHz/1*6 = 60MHz/4 = 10MHz
    PRI_PRESCAL_1_1 |     //1:1 primary prescale
    SEC_PRESCAL_6_1 |     //6:1 secondary prescale
#else
    //spi clock = 40MHz/4*1 = 40MHz/4 = 10MHz
    PRI_PRESCAL_4_1 |     //4:1 primary prescale
    SEC_PRESCAL_1_1 |     //1:1 secondary prescale
#endif
    CLK_POL_ACTIVE_HIGH | //clock active high (CKP = 0)
    SPI_CKE_ON          | //out changes active to inactive (CKE=1)
    SPI_MODE8_ON        | //8-bit mode
    MASTER_ENABLE_ON;     //master mode
  SPI1STATbits.SPIEN = 1;  //enable SPI mode
  //configure pins. Only need SDO, SCLK since POT is output only
#if (defined(__dsPIC33E__) || defined(__PIC24E__))
  //nothing to do here. On this family, the SPI1 port uses dedicated
  //pins for higher speed. The SPI2 port can be used with remappable pins.
  //you may need to add code to disable analog functionality if the SPI ports
  //are on analog-capable pins.
#else
  //all other families (PIC24H/PIC24F/dsPIC33F)
  CONFIG_SDO1_TO_RP(RB6_RP);      //use RB6 for SDO
  CONFIG_RB6_AS_DIG_OUTPUT();   //Ensure that this is a digital output
  CONFIG_SCK1OUT_TO_RP(RB7_RP);   //use RB7 for SCLK
  CONFIG_RB7_AS_DIG_INPUT();   //Ensure that this is a digital input
#endif
  CONFIG_SLAVE_ENABLE();       //chip select for MCP41xxx
  SLAVE_DISABLE();             //disable the chip select
}

void setPotWiper(uint8_t u8_i) {
  SLAVE_ENABLE();         //assert MCP41xxx chipselect
  ioMasterSPI1(0x11);   //command byte to select wiper register
  ioMasterSPI1(u8_i);
  SLAVE_DISABLE();         //negate MCP41xxx chipselect
}

#define BUFSIZE 15
char  sz_1[BUFSIZE+1];

int main (void) {
  uint16_t u16_pv;
  configBasic(HELLO_MSG);
  configSPI1();
  while (1) {
    outString("Input decimal value (0-255): ");
    inString(sz_1,BUFSIZE);
    sscanf(sz_1,"%d",  (int *) &u16_pv);
    printf("\nSending %d to pot.\n",u16_pv);
    setPotWiper(u16_pv & 0x00FF);
  }
}