ADC14.c

// ADC14.c
// Runs on MSP432
// ADC input, software trigger, 14-bit conversion,
// 2.5 V static (always on) reference
// Daniel Valvano
// June 11, 2015

// Modified
// LJBeato
// March 2021

#include <stdint.h>
#include "msp.h"
#include "Common.h"
#include "CortexM.h"
#include "ADC14.h"
//
//
// We are going to use Port 4 Pin 7 which is ADC A6
// P4.7 = A6
//
//
void ADC0_InitSWTriggerCh6(void)
{
	// wait for reference to be idle
	// REF_A->CTL0
  while((REF_A->CTL0&0x400)){};       
		
	// set reference voltage to 2.5V
	// 1) configure reference for static 2.5V
	// REF_A->CTL0
  REF_A->CTL0 = 0x0039;             
		
	// wait for reference voltage to be ready
		// REF_A->CTL0
  while((REF_A->CTL0&0x1000) == 0){};

	// 2) ADC14ENC = 0 to allow programming
	// ADC14->CTL0
  ADC14->CTL0 &= ~BIT1;        

	// 3) wait for BUSY to be zero		
	// ADC14->CTL0
  while(ADC14->CTL0&0x00010000){};   
		
	
	// ------------------------------------------------------------------		
  // 31-30 ADC14PDIV  predivider,            00b = Predivide by 1
  // 29-27 ADC14SHSx  SHM source            000b = ADC14SC bit
  // 26    ADC14SHP   SHM pulse-mode          1b = SAMPCON the sampling timer
  // 25    ADC14ISSH  invert sample-and-hold  0b =  not inverted
  // 24-22 ADC14DIVx  clock divider         000b = /1
  // 21-19 ADC14SSELx clock source select   100b = SMCLK
  // 18-17 ADC14CONSEQx mode select          00b = Single-channel, single-conversion
  // 16    ADC14BUSY  ADC14 busy              0b (read only)
		
  // 15-12 ADC14SHT1x sample-and-hold time 0011b = 32 clocks (use 32 clocks)
		
  // 11-8  ADC14SHT0x sample-and-hold time 0011b = 32 clocks (use 32 clocks)
		
  // 7     ADC14MSC   multiple sample         0b = not multiple
  // 6-5   reserved                          00b (reserved)
  // 4     ADC14ON    ADC14 on                1b = powered up
		
  // 3-2   reserved                          00b (reserved)
  // 1     ADC14ENC   enable conversion       0b = ADC14 disabled
  // 0     ADC14SC    ADC14 start             0b = No start (yet)
	// ------------------------------------------------------------------
	// 4) single, SMCLK, on, disabled, /1, 32 clocks, SHM	pulse-mode
	// ADC14->CTL0
  ADC14->CTL0 = 0x4203310;       
	
	
	
	  // 20-16 STARTADDx  start addr          00000b = ADC14MEM0
  // 15-6  reserved                  0000000000b (reserved)
	// --
  // 5-4   ADC14RES   ADC14 resolution       11b = 14 bit, 16 clocks
	// --
  // 3     ADC14DF    data read-back format   0b = Binary unsigned
  // 2     REFBURST   reference buffer burst  0b = reference on continuously
  // 1-0   ADC14PWRMD ADC power modes        00b = Regular power mode
	//
	// 5) ADC14MEM0, 14-bit, ref on, regular power
	// ADC14->CTL1
  ADC14->CTL1 = 0x30;          
		
		

	// ADC14->MCTL[0]
	// VREF buffered
	// End of sequence
	// 00110b = If ADC14DIF = 0: A6;
	// // 6) 0 to 2.5V, channel 6
  ADC14->MCTL[0] = 0x00000186;         
	
	
	
  // 15   ADC14WINCTH Window comp threshold   0b = not used
  // 14   ADC14WINC   Comparator enable       0b = Comparator disabled
  // 13   ADC14DIF    Differential mode       0b = Single-ended mode enabled
  // 12   reserved                            0b (reserved)
  // 11-8 ADC14VRSEL  V(R+) and V(R-)      0001b = V(R+) = VREF, V(R-) = AVSS
  // 7    ADC14EOS    End of sequence         1b = End of sequence
  // 6-5  reserved                           00b (reserved)
  // 4-0  ADC14INCHx  Input channel        0110b = A6, P4.7
	
	// 7) no interrupts
	// ADC14->IER0
	// ADC14->IER1
  ADC14->IER0 = 0x0;                     
  ADC14->IER1 = 0x0;                     // no interrupts
	//
	// P4.7 is Analog In A6
	// 8) analog mode on A6, P4.7
	// set pins for ADC A6
	// SEL0, SEL1
  P4->SEL0 |= BIT7;                  
  P4->SEL1 |= BIT7;
	
	// 9) enable
	// ADC14->CTL0
  ADC14->CTL0 |= BIT1;         
}


// ADC14->IFGR0 bit 0 is set when conversion done
// cleared on read ADC14MEM0
// ADC14->CLRIFGR0 bit 0, write 1 to clear flag
// ADC14->IVx is 0x0C when ADC14MEM0 interrupt flag; Interrupt Flag: ADC14IFG0
// ADC14->MEM[0] 14-bit conversion in bits 13-0 (31-16 undefined, 15-14 zero)
unsigned int  ADC_In(void)
{
	unsigned int adcIn;
	
	// 1) wait for BUSY to be zero  ADC14->CTL0
	// ADC14->CTL0
  while(ADC14->CTL0&0x00010000){}; 
		
	// 2) start single conversion	  
	// ADC14->CTL0
  ADC14->CTL0 |= BIT0;  

	// 3) wait for ADC14->IFGR0, ADC14->IFGR0 bit 0 is set when conversion done
	// ADC14->IFGR0
  while(!(ADC14->IFGR0&BIT0)){};  
		
	// 14 bit sample returned  ADC14->MEM[0]
	// ADC14->MEM[0] 14-bit conversion in bits 13-0 (31-16 undefined, 15-14 zero)
	// ADC14->MEM[0]
	adcIn = ADC14->MEM[0];
		
  return adcIn;                 // 4) return result 0 to 16383
}