CCS/MSP432P401R: Does parameter adc_pulse_width_X of msp432's adc14 drivelib influence ADC14 sampling rate?

user5229881

Part Number: MSP432P401R

Tool/software: Code Composer Studio

CS_setDCOCenteredFrequency(CS_DCO_FREQUENCY_48);
CS_initClockSignal(CS_SMCLK,CS_DCOCLK_SELECT,CS_CLOCK_DIVIDER_2);

ADC14_enableModule();
ADC14_initModule(ADC_CLOCKSOURCE_SMCLK,ADC_PREDIVIDER_4,ADC_DIVIDER_5,0); //40K

ADC14_setSampleHoldTrigger(ADC_TRIGGER_ADCSC ,false);


ADC14_setSampleHoldTime(ADC_PULSE_WIDTH_64,ADC_PULSE_WIDTH_16);

/* Configuring GPIOs (5.4 A1) */
GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P5, GPIO_PIN7|GPIO_PIN6,
GPIO_TERTIARY_MODULE_FUNCTION);
P8SEL1|=BIT6;
P8SEL0|=BIT6;

/* Configuring ADC Memory */
MAP_ADC14_configureSingleSampleMode(ADC_MEM0, true);
MAP_ADC14_configureConversionMemory(ADC_MEM0, ADC_VREFPOS_EXTPOS_VREFNEG_EXTNEG,
ADC_INPUT_A19, false);

/* Configuring Sample Timer */
ADC14_enableSampleTimer(ADC_MANUAL_ITERATION);
//ADC14_enableSampleTimer(ADC_AUTOMATIC_ITERATION);
/* Enabling/Toggling Conversion */
MAP_ADC14_enableConversion();
MAP_ADC14_toggleConversionTrigger();

/* Enabling interrupts */
MAP_ADC14_enableInterrupt(ADC_INT0);
MAP_Interrupt_enableInterrupt(INT_ADC14);
MAP_Interrupt_enableMaster();
/*Set resolution*/
ADC14_setResolution(ADC_14BIT);

ADC14_setSampleHoldTime(ADC_PULSE_WIDTH_64,ADC_PULSE_WIDTH_16),this configration does influence ADC sample rate,does it mean ADC sample rate 48M/2/4/5/(64+16)=15KHz?

and what difference between ADC14_enableSampleTimer(ADC_MANUAL_ITERATION) and ADC_AUTOMATIC_ITERATION?

over 6 years ago

0 Sai Reddy over 6 years ago

TI__Mastermind 22580 points

Hello,

Looks like you are already being helped on a similar post - e2e.ti.com/.../783690

Since that post is open and actively being replied to, I will close this post.

In the future, if possible please avoid opening duplicate threads.

Thanks,
Sai

0 user5229881 over 6 years ago in reply to Sai Reddy

Prodigy 235 points

but i do not get what i want to know,plz tell me the ADC sample rate is right or not .

0 Chris Sterzik over 6 years ago in reply to user5229881

TI__Guru 65141 points

Please see the TRM for a more detailed description of the Sample and Conversion Time. In Table 22-1 you will see three modes; pulse sample mode with ADC14MSC = 0, pulse sample mode with ADC14MSC = 1, and extended sample mode. In your example above you make the following call:

ADC14_enableSampleTimer(ADC_MANUAL_ITERATION);

This means that the mode is pulse sample mode with ADC14MSC = 0. This means that the total time will be 23 ADCClock cycles plus the number of clock cycles defined for the sample time. So for example if you chose 16 samples, then the total time would be 39 clocks. Because the trigger is the start covert bit (SC) and the ADC_MANUAL_ITERATION is used that means that the actual rate at which you sample will be dictated by how often you toggle the SC bit. It is possible to toggle or trigger the ADC before the current conversion is complete. In this case, i believe it just ignores the trigger.

Regards,

Chris

0 user5229881 over 6 years ago in reply to Chris Sterzik

Prodigy 235 points

Timer_A_UpModeConfig upModeConfig =
{
TIMER_A_CLOCKSOURCE_SMCLK,
TIMER_A_CLOCKSOURCE_DIVIDER_4,
149,
TIMER_A_TAIE_INTERRUPT_DISABLE,
TIMER_A_CCIE_CCR0_INTRRUPT_DISABLE,
TIMER_A_DO_CLEAR
};

ADC14_setSampleHoldTrigger(ADC_TRIGGER_Timer_A ,false);

does it means sample rate is 24M/4/(149+1)=40K
so adc sample rate is 40K,what difference is between ADC_TRIGGER_Timer_A and ADC_TRIGGER_ADCSC?
what SC in "ADC_TRIGGER_ADCSC " exactly mean? is it clk from divided SMCLK?
how i get adc sample by ADC_TRIGGER_Timer_A ？

0 user5229881 over 6 years ago in reply to Chris Sterzik

Prodigy 235 points

“This means that the total time will be 23 ADCClock cycles ” in your reply , why is 23? i know 16 is from the last of ADC14_setSampleHoldTime(ADC_PULSE_WIDTH_64,ADC_PULSE_WIDTH_16);