The MSP-EXP430FR5739 board has a built in AXL335 which is a 3-axis accelerometer. It is hard wired to ports P3.0, P3.1, and P3.2. There was no demo code how to get the ADC10 to read those values.
I looked into the sequential sampling that the MSP430 supports which is where ADC10INCHx is set to the last ADC port and will go all the way down to ADC10INCH0 in sequence. This is a problem on the Fraunch Pad as the AXL335 outputs are wired to P3.0 – P3.2 which means when you set ADC10INCHx to ADC10INCH14 (P3.2) it will process more then half the pins as analog inputs!
Solution was to change the ADC10INCHx between sampling so the ADC process became round robin style. Here is the working code to sample all the axises on the Fraunch board. Also included is the “zero” calibration routines.
This code also contains a twin servo routine. The servos are connected to P1.4 and P1.5. When the X-axis moves the servo on P1.4 moves and when the Y-axis moves the servo on P1.5.
Code
main.c
FR_EXP.h
#include "msp430fr5739.h"
#include "FR_EXP.h"
#define SERVO_1 BIT4
#define SERVO_2 BIT5
#define scale 9
unsigned int servo_counter = 0;
unsigned int servo1pos = 1500;
unsigned int servo2pos = 1500;
unsigned int ADC_counter = 0;
unsigned int ADCResult_X, ADCResult_Y, ADCResult_Z;
unsigned int CalValue_X, CalValue_Y, CalValue_Z;
unsigned int temp;
void main(void)
{
WDTCTL = WDTPW + WDTHOLD; //Stop the dog
SystemInit(); //Setup the pins
StartUpSequence(); //Copy Ti's fancy LED boot up trick
SetupAccel(); //Setup the ADC and Accel
CalibrateADC(); //Find zero points of all 3 axis
ADC10CTL0 |= ADC10ENC | ADC10SC; //Start the first sample. If this is not done the ADC10 interupt will not trigger.
while (1)
{
if (ADCResult_X > CalValue_X + 10)
{
servo1pos = 1500 + scale * (ADCResult_X - CalValue_X);
if (servo1pos > 2500)
{
servo1pos = 2500;
}
}
else if (ADCResult_X < CalValue_X - 10)
{
servo1pos = 1500 - scale * (CalValue_X - ADCResult_X);
if (servo1pos < 500)
{
servo1pos = 500;
}
}
else
{
servo1pos = 1500;
}
if (ADCResult_Y > CalValue_Y + 10)
{
servo2pos = 1500 + scale * (ADCResult_Y - CalValue_Y);
if (servo2pos > 2500)
{
servo2pos = 2500;
}
}
else if (ADCResult_Y < CalValue_Y - 10)
{
servo2pos = 1500 - scale * (CalValue_Y - ADCResult_Y);
if (servo2pos < 500)
{
servo2pos = 500;
}
}
else
{
servo2pos = 1500;
}
}
}
void SystemInit(void) //Sets up the Fraunch board for Accel reads and LED tricks
{
//Startup clock system in max. DCO setting ~8MHz
// This value is closer to 10MHz on untrimmed parts
CSCTL0_H = 0xA5; // Unlock register
CSCTL1 |= DCOFSEL0 + DCOFSEL1; // Set max. DCO setting
CSCTL2 = SELA_1 + SELS_3 + SELM_3; // set ACLK = vlo; MCLK = DCO
CSCTL3 = DIVA_0 + DIVS_0 + DIVM_0; // set all dividers
CSCTL0_H = 0x01; // Lock Register
// Turn off temp.
REFCTL0 |= REFTCOFF;
REFCTL0 &= ~REFON;
// Enable LEDs
P3OUT &= ~(BIT6+BIT7+BIT5+BIT4);
P3DIR |= BIT6+BIT7+BIT5+BIT4;
PJOUT &= ~(BIT0+BIT1+BIT2+BIT3);
PJDIR |= BIT0 +BIT1+BIT2+BIT3;
// P3.0,P3.1 and P3.2 are accelerometer inputs
P3OUT &= ~(BIT0 + BIT1 + BIT2);
P3DIR &= ~(BIT0 + BIT1 + BIT2);
P3REN |= BIT0 + BIT1 + BIT2;
// Setup Servo ports
P1OUT &= ~(SERVO_1 + SERVO_2);
P1DIR |= SERVO_1 + SERVO_2;
P1SEL0 &= ~(SERVO_1 + SERVO_2);
P1SEL1 &= ~(SERVO_1 + SERVO_2);
// Setup Servo Interrupt
TA0CCTL0 = CCIE;
TA0CCR0 = 1500;
TA0CTL = TASSEL_2 + MC_1 + ID_3;
}
void CalibrateADC(void) //Sets the "zero" point of the accelerometer
{
unsigned char CalibCounter =0;
unsigned int Value = 0;
__disable_interrupt(); //Turn off any interupts just incase
ADC10CTL0 &= ~ADC10ENC; //Toggle ENC bit. Need this to change the ADC10INCH_x value.
ADC10MCTL0 = ADC10SREF_0 + ADC10INCH_12; //Sample the X-axis
while(CalibCounter <50)
{
P3OUT ^= BIT4;
CalibCounter++;
ADC10CTL0 |= ADC10ENC | ADC10SC; //Start sample.
while (ADC10CTL1 & BUSY); //Wait for sample to be done.
Value += ADC10MEM0;
}
CalValue_X = Value/50; //Average all samples to find the best zero.
ADC10CTL0 &= ~ADC10ENC; //Toggle ENC bit. Need this to change the ADC10INCH_x value.
CalibCounter = 0; //Reset the counters
Value = 0;
ADC10MCTL0 = ADC10SREF_0 + ADC10INCH_13; //Sample the Y-axis
while(CalibCounter <50)
{
P3OUT ^= BIT4;
CalibCounter++;
ADC10CTL0 |= ADC10ENC | ADC10SC; //Start sample.
while (ADC10CTL1 & BUSY); //Wait for sample to be done.
Value += ADC10MEM0;
}
CalValue_Y = Value/50; //Average all samples to find the best zero.
ADC10CTL0 &= ~ADC10ENC; //Toggle ENC bit. Need this to change the ADC10INCH_x value.
CalibCounter = 0; //Reset the counters
Value = 0;
ADC10MCTL0 = ADC10SREF_0 + ADC10INCH_14; //Sampel the Z-axis
while(CalibCounter <50)
{
P3OUT ^= BIT4;
CalibCounter++;
ADC10CTL0 |= ADC10ENC | ADC10SC; //Start sample.
while (ADC10CTL1 & BUSY); //Wait for sample to be done.
Value += ADC10MEM0;
}
CalValue_Z = Value/50; //Average all samples to find the best zero.
ADC10CTL0 &= ~ADC10ENC; //Toggle ENC bit. Need this to change the ADC10INCH_x value.
ADC10MCTL0 = ADC10SREF_0 + ADC10INCH_12; //We need to start at the X-axis first due to how the interupt routine works.
__enable_interrupt(); //enable interupts
}
void SetupAccel(void)
{
//Setup accelerometer
// ~20KHz sampling
//Configure GPIO
ACC_PORT_SEL0 |= ACC_X_PIN + ACC_Y_PIN + ACC_Z_PIN; //Enable A/D channel inputs
ACC_PORT_SEL1 |= ACC_X_PIN + ACC_Y_PIN + ACC_Z_PIN;
ACC_PORT_DIR &= ~(ACC_X_PIN + ACC_Y_PIN + ACC_Z_PIN);
ACC_PWR_PORT_DIR |= ACC_PWR_PIN; //Enable ACC_POWER
ACC_PWR_PORT_OUT |= ACC_PWR_PIN;
// Allow the accelerometer to settle before sampling any data
__delay_cycles(200000);
//Setting up the ADC stuff
ADC10CTL0 &= ~ADC10ENC; // Ensure ENC is clear
ADC10CTL0 = ADC10ON + ADC10SHT_5;
ADC10CTL1 = ADC10SHS_0 + ADC10SHP + ADC10CONSEQ_0 + ADC10SSEL_0;
ADC10CTL2 = ADC10RES;
ADC10MCTL0 = ADC10SREF_0 + ADC10INCH_12;
ADC10IV = 0x00; //Clear all ADC12 channel int flags
ADC10IE |= ADC10IE0; //Enable ADC10 interrupts
__enable_interrupt();
}
void StartUpSequence(void) //this is copied from the Ti Fraunch Pad experience. Only thing it does is make a fancy LED sequence on boot.
{
unsigned char flag=4,up=1,counter = 0;
unsigned char LED_ArrayPJ[] = {0x01,0x02,0x04,0x08};
unsigned char LED_ArrayP3[] = {0x80,0x40,0x20,0x10};
while (counter <10)
{
counter++;
PJOUT &= ~(BIT0 +BIT1+BIT2+BIT3);
P3OUT &= ~(BIT4 +BIT5+BIT6+BIT7);
if(up)
{
while(flag)
{
P3OUT = LED_ArrayP3[flag-1];
PJOUT = LED_ArrayPJ[flag-1];
LongDelay();
flag--;
}
up=0;
}
else
{
while(flag<4)
{
P3OUT = LED_ArrayP3[flag];
PJOUT = LED_ArrayPJ[flag];
LongDelay();
flag++;
}
up = 1;
}
}
PJOUT &= ~(BIT0 +BIT1+BIT2+BIT3);
P3OUT &= ~(BIT4 +BIT5+BIT6+BIT7);
}
void LongDelay()
{
__delay_cycles(250000);
}
//Servo Interrupt
#pragma vector = TIMER0_A0_VECTOR
__interrupt void Timer_A (void)
{
if(servo_counter == 0)
{
P1OUT |= SERVO_1;
P1OUT |= SERVO_2;
if (servo1pos >= servo2pos)
{
TA0CCR0 = servo2pos;
}
else
{
TA0CCR0 = servo1pos;
}
servo_counter++;
}
else if(servo_counter == 1)
{
if (servo1pos >= servo2pos)
{
P1OUT &= ~(SERVO_2);
TA0CCR0 = servo1pos - servo2pos;
}
else
{
P1OUT &= ~(SERVO_1);
TA0CCR0 = servo2pos - servo1pos;
}
servo_counter++;
}
else
{
TA0CCR0 = 20000 - servo1pos;
P1OUT &= ~(SERVO_1);
P1OUT &= ~(SERVO_2);
servo_counter = 0;
}
}
//ADC10 interupt routine
#pragma vector = ADC10_VECTOR
__interrupt void ADC10_ISR(void)
{
if (ADC_counter == 0) //X-axis
{
ADC10CTL0 &= ~ADC10ENC;
ADC10MCTL0 = ADC10SREF_0 + ADC10INCH_13; //Next channel is the Y-axis
ADCResult_X = ADC10MEM0;
ADC_counter++;
ADC10CTL0 |= ADC10ENC | ADC10SC;
}
else if (ADC_counter == 1) //Y-axis
{
ADC10CTL0 &= ~ADC10ENC;
ADC10MCTL0 = ADC10SREF_0 + ADC10INCH_14; //Next channel is the Z-axis
ADCResult_Y = ADC10MEM0;
ADC_counter++;
ADC10CTL0 |= ADC10ENC | ADC10SC;
}
else //Z-axis
{
ADC10CTL0 &= ~ADC10ENC;
ADC10MCTL0 = ADC10SREF_0 + ADC10INCH_12; //Next channel is the X-axis
ADCResult_Z = ADC10MEM0;
ADC_counter = 0;
ADC10CTL0 |= ADC10ENC | ADC10SC;
}
}
