chap11/adc7scan1_dma.c

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/*
 * "Copyright (c) 2008 Robert B. Reese, Bryan A. Jones, J. W. Bruce ("AUTHORS")"
 * All rights reserved.
 * (R. Reese, reese_AT_ece.msstate.edu, Mississippi State University)
 * (B. A. Jones, bjones_AT_ece.msstate.edu, Mississippi State University)
 * (J. W. Bruce, jwbruce_AT_ece.msstate.edu, Mississippi State University)
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose, without fee, and without written agreement is
 * hereby granted, provided that the above copyright notice, the following
 * two paragraphs and the authors appear in all copies of this software.
 *
 * IN NO EVENT SHALL THE "AUTHORS" BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
 * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE "AUTHORS"
 * HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * THE "AUTHORS" SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE "AUTHORS" HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS."
 *
 * Please maintain this header in its entirety when copying/modifying
 * these files.
 *
 *
 */

#include "pic24_all.h"
#include "stdio.h"


#ifndef _DMA0IF
#error "This processor selection does not have a DMA module; this code example is incompatible with a PIC24 CPU that does not have DMA."

#endif

#define CONFIG_LED2()       CONFIG_RB14_AS_DIG_OUTPUT()
#define LED2                _LATB14


// uncomment the next line to setup this project for a 12-bit ADC
//#define USE_12BIT_ADC

#ifdef  USE_12BIT_ADC
#define   ADC_LEN           12
#define   ADC_NSTEPS        4096
#define   ADC_12BIT_FLAG    1
#else
#define   ADC_LEN           10
#define   ADC_NSTEPS        1024
#define   ADC_12BIT_FLAG    0
#endif



/***
 *** HERE IS THE CODE!
 ***
 ***/

// set this to one of the values of 
// 1, 2, 4, 8, 16, 32, 64, 128 
#define CONVERSIONS_PER_INPUT  1 
#define MAX_CHANNELS   16
//DMA transfer size is in words.
#define MAX_DMA_TRANSFER_SIZE (CONVERSIONS_PER_INPUT*MAX_CHANNELS)   //make power of two for alignment to work

//DMA buffers, alignment is based on number of bytes
uint16 au16_bufferA[MAX_DMA_TRANSFER_SIZE] __attribute__((space(dma),aligned(MAX_DMA_TRANSFER_SIZE*2)));

//generic DMA/ADC configuration function, enables scanning, uses DMA channel 0
//returns the number of channels that are scanned as specified by the mask.
uint8 configDMA_ADC(uint16   u16_ch0ScanMask, \
                               uint8    u8_autoSampleTime, \
                               uint8    u8_use12bit,
                               uint8    u8_useScatterGather,
                               uint8    u8_dmaLocsPerInput) {
  uint8     u8_i, u8_nChannels=0;
  uint16    u16_mask = 0x0001;
  uint16    u16_dmaMode;
 

  // compute the number of Channels the user wants to scan over
  for (u8_i=0; u8_i<16; u8_i++) {
    if (u16_ch0ScanMask & u16_mask)
      u8_nChannels++;
    u16_mask<<=1;
  } //end for

  if (u8_autoSampleTime > 31) u8_autoSampleTime=31;

  AD1CON1bits.ADON = 0;   // turn off ADC (changing setting while ADON is not allowed)
  AD1CON1 = ADC_CLK_AUTO | ADC_AUTO_SAMPLING_ON;
#ifdef _AD12B
  if (u8_use12bit)
    AD1CON1bits.AD12B = 1;
  else
    AD1CON1bits.AD12B = 0;
#endif
   if (u8_useScatterGather) {
         AD1CON1bits.ADDMABM = 0;
         u16_dmaMode = DMA_AMODE_PERIPHERAL_INDIRECT;         
   }
   else {
      //order mode
      AD1CON1bits.ADDMABM = 1;
      u16_dmaMode = DMA_AMODE_REGISTER_POSTINC;
   } 
   AD1CON3 = ADC_CONV_CLK_INTERNAL_RC | (u8_autoSampleTime<<8);
   //Note: PIC24H family reference manual (16.13.2) says that for 'ordered' mode, the
   //SMPI bits should be cleared. However, when scanning, this seems to be incorrect as the  
   //settings that work are the same ones used for 'scatter/gather' mode.
   AD1CON2 = ADC_VREF_AVDD_AVSS | ADC_CONVERT_CH0 | ADC_SCAN_ON | ((u8_nChannels-1)<<2);
  
#ifdef __PIC24H__
  AD1CHS0 = ADC_CH0_NEG_SAMPLEA_VREFN;
#else
  AD1CHS = ADC_CH0_NEG_SAMPLEA_VREFN;
#endif
  AD1CSSL = u16_ch0ScanMask;

  //AD1CON4 is only used in scatter-gather mode
  switch (u8_dmaLocsPerInput) {
   case 1   :  AD1CON4 = ADC_1_WORD_PER_INPUT;break;
   case 2   :  AD1CON4 = ADC_2_WORD_PER_INPUT;break;
   case 4   :  AD1CON4 = ADC_4_WORD_PER_INPUT;break;
   case 8   :  AD1CON4 = ADC_8_WORD_PER_INPUT;break;
   case 16  :  AD1CON4 = ADC_16_WORD_PER_INPUT;break;
   case 32  :  AD1CON4 = ADC_32_WORD_PER_INPUT;break;
   case 64  :  AD1CON4 = ADC_64_WORD_PER_INPUT;break;
   case 128 :  AD1CON4 = ADC_128_WORD_PER_INPUT;break;
    default: AD1CON4 = ADC_1_WORD_PER_INPUT;break;
  }
 
 //configure the DMA channel 0 interrupt 
  DMA0PAD = (unsigned int) &ADC1BUF0;
  DMA0REQ = DMA_IRQ_ADC1;
  DMA0STA = __builtin_dmaoffset(au16_bufferA);
  DMA0CNT = (u8_nChannels * u8_dmaLocsPerInput)-1; 
  DMA0CON =   //configure and enable the module Module
    (DMA_MODULE_ON |
     DMA_SIZE_WORD |
     DMA_DIR_READ_PERIPHERAL |
     DMA_INTERRUPT_FULL |
     DMA_NULLW_OFF |
     u16_dmaMode |
     DMA_MODE_CONTINUOUS);

   _DMA0IF = 0;
   _DMA0IP = 6;
   _DMA0IE = 1; 

   AD1CON1bits.ADON = 1;   // turn on the ADC 
   return(u8_nChannels);
}

volatile  uint16    au16_buffer[MAX_DMA_TRANSFER_SIZE];
volatile  uint8     u8_waiting;


void _ISRFAST _DMA0Interrupt(void) {
  uint8       u8_i;
  uint16*     au16_adcHWBuff = (uint16*) &au16_bufferA;
  _DMA0IF = 0;
  if (u8_waiting ) {
   for ( u8_i=0; u8_i<MAX_DMA_TRANSFER_SIZE; u8_i++) {
     au16_buffer[u8_i] = au16_adcHWBuff[u8_i];
   } //end for()
   u8_waiting = 0;  // signal main() that data is ready
  }
   // toggle a port pin so that we can measure how often DMA IRQs are coming in
  LED2 = !LED2;
}



int main (void) {
  uint8   u8_i, u8_j, u8_k;
  uint16  u16_sum;
  uint16  u16_pot;
  float   f_pot;

  configBasic(HELLO_MSG);

  // make RA0/AN0/VREF+ a digital input to kill the pullup and
  // set the TRISA bit, then make it ANALOG so the ADC will work
  CONFIG_AN0_AS_ANALOG();
  CONFIG_AN1_AS_ANALOG();
  CONFIG_AN4_AS_ANALOG();
  CONFIG_AN5_AS_ANALOG();
  CONFIG_AN10_AS_ANALOG();
  CONFIG_AN11_AS_ANALOG();
  CONFIG_AN12_AS_ANALOG();

  CONFIG_LED2();  

  configDMA_ADC( ADC_SCAN_AN0 | ADC_SCAN_AN1 | ADC_SCAN_AN4 |    \
                             ADC_SCAN_AN5 | ADC_SCAN_AN10 | ADC_SCAN_AN11 | ADC_SCAN_AN12,
                             31, ADC_12BIT_FLAG, 1, CONVERSIONS_PER_INPUT);



  // wait for first conversion to finish before proceeding
  while ( !AD1CON1bits.DONE) {};
  u8_waiting = 1;
  while (1) {
    while (u8_waiting){};  // wait for valid data in ISR 
    //data is updated in array by DMA ISR when u8_waiting flag is cleared  
    //iterate over channels, and average results for each channel 
        //data in array will not be updated again by DMA ISR until u8_waiting flag is set.
    u8_k = 0;  //buffer index 
    for ( u8_i=0; u8_i<16; u8_i++) {  //each channel 
      for (u8_j=0; u8_j<CONVERSIONS_PER_INPUT; u8_j++) {  //each result per channel
         if (u8_j == 0) u16_sum = au16_buffer[u8_k];
            else u16_sum += au16_buffer[u8_k];
         u8_k++;
      }
      u16_pot = u16_sum/CONVERSIONS_PER_INPUT; //take the average
      f_pot = 3.3 / ADC_NSTEPS * u16_pot;
      printf("r");
      if (u8_i < 10) outChar( '0'+u8_i );
      else outChar( 'A'-10+u8_i );
      printf(":0x%04X=%1.3fV  ",  u16_pot, (double) f_pot );
      if ((u8_i % 4) == 3) printf("\n");
    } //end for()
    printf("\n");
    u8_waiting = 1;      
    doHeartbeat();
    DELAY_MS(1500);
  } //endof while()
} // endof main()

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