AnalogRead() Faster

Will,

is using Energia mandatory for you? Or would you use the "normal" programming in Code Composer / IAR as well?

I'd Prefer Energia. The learning curve is not as steep for a one off project. Would simply changing the clock divider and idle time be enough?

I'm confused on what specific values need to be changed here. As you can see I have changed the divider from 4 > 1 and delay Cycles I cut in half.

uint16_t analogRead(uint8_t pin)
{
// make sure we have an ADC
uint8_t channel;

// Check if pin is a special analog pin (A10 = temp sensor, A11 = Vcc/2, etc.)
if (pin >=128)
channel = pin - 128;
else
channel = digitalPinToADCIn(pin);

// Check if pin is valid
if (pin==NOT_ON_ADC)
return 0;
#if defined(__MSP430_HAS_ADC10__) || defined(__MSP430_HAS_ADC10_B__) || defined(__MSP430_HAS_ADC12_PLUS__) || defined(__MSP430_HAS_ADC12_B__) || defined(__MSP430_HAS_ADC__)
// 0000 A0
// 0001 A1
// 0010 A2
// 0011 A3
// 0100 A4
// 0101 A5
// 0110 A6
// 0111 A7
// 1010 Internal temperature sensor

//TODO: Only int. temp. sensor requires Tsample > 30us.
// The below ADC configuration applies this rule to all channels right now.
// ADC10CLK = 5MHz / 5 = 1Mhz
// Tsample = S&H / ADC10CLK = 64 / 1 MHz = 64 us
// Tconvert = 13 / ADC10CLK = 13 / 1 MHz = 13 us
// Total time per sample = Tconvert + Tsample = 64 + 13 = 67 us = ~15k samples / sec

#if defined(__MSP430_HAS_ADC10__)
ADC10CTL0 &= ~ADC10ENC; // disable ADC
ADC10CTL1 = ADC10SSEL_0 | ADC10DIV_1; // ADC10OSC as ADC10CLK (~5MHz) / 5
ADC10CTL0 = analog_reference | // set analog reference
ADC10ON | ADC10SHT_3 | ADC10IE; // turn ADC ON; sample + hold @ 64 × ADC10CLKs; Enable interrupts
ADC10CTL1 |= (channel << 12); // select channel
ADC10AE0 = (1 << channel); // Disable input/output buffer on pin
__delay_cycles(64); // Delay to allow Ref to settle
ADC10CTL0 |= ADC10ENC | ADC10SC; // enable ADC and start conversion
while (ADC10CTL1 & ADC10BUSY) { // sleep and wait for completion
__bis_SR_register(CPUOFF + GIE); // LPM0 with interrupts enabled
}
/* POWER: Turn ADC and reference voltage off to conserve power */
ADC10CTL0 &= ~(ADC10ON | REFON);
#endif
#if defined(__MSP430_HAS_ADC10_B__)
ADC10CTL0 &= ~ADC10ENC; // disable ADC
ADC10CTL1 = ADC10SSEL_0 | ADC10DIV_1; // ADC10OSC as ADC10CLK (~5MHz) / 5
while(REFCTL0 & REFGENBUSY); // If ref generator busy, WAIT
REFCTL0 |= analog_reference & REF_MASK; // Set reference using masking off the SREF bits. See Energia.h.
ADC10MCTL0 = channel | (analog_reference & REFV_MASK); // set channel and reference
ADC10CTL0 = ADC10ON | ADC10SHT_4; // turn ADC ON; sample + hold @ 64 × ADC10CLKs
ADC10CTL1 |= ADC10SHP; // ADCCLK = MODOSC; sampling timer
ADC10CTL2 |= ADC10RES; // 10-bit resolution
ADC10IFG = 0; // Clear Flags
ADC10IE |= ADC10IE0; // Enable interrupts
__delay_cycles(64); // Delay to allow Ref to settle
ADC10CTL0 |= ADC10ENC | ADC10SC; // enable ADC and start conversion
while (ADC10CTL1 & ADC10BUSY) { // sleep and wait for completion
__bis_SR_register(CPUOFF + GIE); // LPM0 with interrupts enabled
}
/* POWER: Turn ADC and reference voltage off to conserve power */
ADC10CTL0 &= ~(ADC10ON);
REFCTL0 &= ~REFON;
#endif
#if defined(__MSP430_HAS_ADC__)
ADCCTL0 &= ~ADCENC; // disable ADC
ADCCTL1 = ADCSSEL_0 | ADCDIV_1; // ADC10OSC as ADC10CLK (~5MHz) / 5
//REFCTL0 |= analog_reference & REF_MASK; // Set reference using masking off the SREF bits. See Energia.h.
PMMCTL0_H = PMMPW_H; // open PMM
PMMCTL2 |= INTREFEN; // enable Ref
if (pin == TEMPSENSOR) PMMCTL2 |= TSENSOREN; // enable TC
ADCMCTL0 = channel | (analog_reference & REFV_MASK); // set channel and reference
ADCCTL0 = ADCON | ADCSHT_4; // turn ADC ON; sample + hold @ 64 × ADC10CLKs
ADCCTL1 |= ADCSHP; // ADCCLK = MODOSC; sampling timer
ADCCTL2 |= ADCRES; // 10-bit resolution
ADCIFG = 0; // Clear Flags
ADCIE |= ADCIE0; // Enable interrupts
__delay_cycles(64); // Delay to allow Ref to settle
ADCCTL0 |= ADCENC | ADCSC; // enable ADC and start conversion
while (ADCCTL1 & ADCBUSY) { // sleep and wait for completion
__bis_SR_register(CPUOFF + GIE); // LPM0 with interrupts enabled
}
/* POWER: Turn ADC and reference voltage off to conserve power */
ADCCTL0 &= ~(ADCON);
//REFCTL0 &= ~REFON;
PMMCTL2 &= ~(INTREFEN | TSENSOREN);
PMMCTL0_H = 0; // close PMM
#endif
#if defined(__MSP430_HAS_ADC12_PLUS__)
ADC12CTL0 &= ~ADC12ENC; // disable ADC
ADC12CTL1 = ADC12SSEL_0 | ADC12DIV_1; // ADC12OSC as ADC12CLK (~5MHz) / 5
while(REFCTL0 & REFGENBUSY); // If ref generator busy, WAIT
if (pin == TEMPSENSOR) {// if Temp Sensor
REFCTL0 = (INTERNAL1V5 & REF_MASK); // Set reference to internal 1.5V
ADC12MCTL0 = channel | ((INTERNAL1V5 >> 4) & REFV_MASK); // set channel and reference
} else {
REFCTL0 = (analog_reference & REF_MASK); // Set reference using masking off the SREF bits. See Energia.h.
ADC12MCTL0 = channel | ((analog_reference >> 4) & REFV_MASK); // set channel and reference
}
ADC12CTL0 = ADC12ON | ADC12SHT0_4; // turn ADC ON; sample + hold @ 64 × ADC10CLKs
ADC12CTL1 |= ADC12SHP; // ADCCLK = MODOSC; sampling timer
ADC12CTL2 |= ADC12RES1; // 12-bit resolution
ADC12IFG = 0; // Clear Flags
ADC12IE |= ADC12IE0; // Enable interrupts
__delay_cycles(128); // Delay to allow Ref to settle
ADC12CTL0 |= ADC12ENC | ADC12SC; // enable ADC and start conversion
while (ADC12CTL1 & ADC12BUSY) { // sleep and wait for completion
__bis_SR_register(CPUOFF + GIE); // LPM0 with interrupts enabled
}
/* POWER: Turn ADC and reference voltage off to conserve power */
ADC12CTL0 &= ~(ADC12ON);
REFCTL0 &= ~REFON;
#endif
#if defined(__MSP430_HAS_ADC12_B__)
ADC12CTL0 &= ~ADC12ENC; // disable ADC
ADC12CTL0 = ADC12ON | ADC12SHT0_4; // turn ADC ON; sample + hold @ 64 × ADC12CLKs
ADC12CTL1 = ADC12SSEL_0 | ADC12DIV_1; // ADC12OSC as ADC12CLK (~5MHz) / 5
ADC12CTL3 = ADC12TCMAP | ADC12BATMAP; // Map Temp and BAT
ADC12CTL1 |= ADC12SHP; // ADCCLK = MODOSC; sampling timer
ADC12CTL2 |= ADC12RES_2; // 12-bit resolution
ADC12IFGR0 = 0; // Clear Flags
ADC12IER0 |= ADC12IE0; // Enable interrupts
while(REFCTL0 & REFGENBUSY); // If ref generator busy, WAIT
if (pin == TEMPSENSOR) {// if Temp Sensor
REFCTL0 = (INTERNAL1V2 & REF_MASK); // Set reference to internal 1.2V
ADC12MCTL0 = channel | (INTERNAL1V2 & REFV_MASK); // set channel and reference
} else {
REFCTL0 = (analog_reference & REF_MASK); // Set reference using masking off the SREF bits. See Energia.h.
ADC12MCTL0 = channel | (analog_reference & REFV_MASK); // set channel and reference
}
if (REFCTL0 & REFON)
while(!(REFCTL0 & REFGENRDY)); // wait till ref generator ready
ADC12CTL0 |= ADC12ENC | ADC12SC; // enable ADC and start conversion
while (ADC12CTL1 & ADC12BUSY) { // sleep and wait for completion
__bis_SR_register(CPUOFF + GIE); // LPM0 with interrupts enabled
}
/* POWER: Turn ADC and reference voltage off to conserve power */
ADC12CTL0 &= ~(ADC12ON);
REFCTL0 &= ~(REFON);
#endif
return ADCxMEM0; // return sampled value after returning to active mode in ADC10_ISR

You could try to increase the ADC clock, or reduce its accuracy (number of cycles).

But the main problem with Energia is that the analogRead() function must work independently, i.e., it configures the ADC and REF, starts the ADC conversion, and then waits for it to finish.

To get maximum speed out of the ADC, you should configure it once (when the program starts) to run continuously, and let the conversion happen concurrently with your code (i.e., the ADC captures the next value while your code is handling the previous value).