ADC Burst?

bmildh — Tue, 07 Sep 2021 08:28:20 GMT

I'm trying to get ADC Burst working on my LPC1758, but It seems like my ADC ISR does not fire. If anyone could shed some light on this I would be most grateful.

The way that I think I understand it, burst-mode should give me continuous ADC conversion on the channels that I select. If I have selected channel 2,4,5 and 7, and also enable the interrupt for channel 7, then, when channel 7 finish a conversion, I should be able to harvest the values for channel 2,4,5 and 7.

This is my initialization:

#define SBIT_AD0_CLCKDIV 8u // ADC0CR (Bits 15:8) #define SBIT_AD0_BURST 16u // ADC0CR #define SBIT_AD0_PDN 21u // ADC0CR #define SBIT_AD0_START 24u // ADC0CR (Bits 26:24) #define SBIT_AD0_EDGE 27u // ADC0CR #define SBIT_AD0_ADGINTEN 8u // AD0INTEN #define SBIT_AD0_PCADC 12u // PCONP #define SBIT_AD0_INTEN2 2u #define SBIT_AD0_INTEN4 4u // AD0INTEN #define SBIT_AD0_INTEN5 5u #define SBIT_AD0_INTEN7 7u void Init_ADC(void) { set_PINSEL(0,25,1); // Ch 2 set_PINSEL(1,30,3); // Ch 4 set_PINSEL(1,31,3); // Ch 5 set_PINSEL(0,2,2); // Ch 7 // No pull-up no pull-down (function ADC) set_PINMODE(0,25,NOPULL); // Ch 2 set_PINMODE(1,30,NOPULL); // Ch 4 set_PINMODE(1,31,NOPULL); // Ch 5 set_PINMODE(0,2,NOPULL); // Ch 7 // ADC enabled, turning on power LPC_SC->PCONP |= (1<<SBIT_AD0_PCADC); // Stop ADC (in burst mode this should be 000) LPC_ADC->CR &= ~(7<<SBIT_AD0_START); // Enable interrupt on all of the selected channels LPC_ADC->INTEN &= ~(1<<SBIT_AD0_ADGINTEN); LPC_ADC->INTEN |= (1<<SBIT_AD0_INTEN7) | (1<<SBIT_AD0_INTEN2) | (1<<SBIT_AD0_INTEN4) | (1<<SBIT_AD0_INTEN5); // Select channel 2,4,5,7 LPC_ADC->CR |= ((1<<2) | (1<<4) | (1<<5) | (1<<7)); // PCLK = CCLK / 2 => 40Mhz; We divide the PCLK with 4 and get 10Mhz. // The ADC clock should be 13Mhz or slightly less (see doc) LPC_ADC->CR |= ((4-1)<<SBIT_AD0_CLCKDIV); // Enable burst mode LPC_ADC->CR |= (1<<SBIT_AD0_BURST); // ADC operational LPC_ADC->CR |= (1<<SBIT_AD0_PDN); NVIC_EnableIRQ(ADC_IRQn); }

And this is my ISR: (right now I'm only interesting in the ADCbusyflag. I just want to know if this flag is set. In my main loop I print out on serial every second, the value of ADCbusyflag. The value is always zero, indicating that the ISR is never called. Also, the STAT register of the ADC is always zero.

void ADC_IRQHandler(void) { ADCmean[7] = ((LPC_ADC->DR[7]>>4) & 0x0FFF); ADCmean[5] = ((LPC_ADC->DR[5]>>4) & 0x0FFF); ADCmean[2] = ((LPC_ADC->DR[2]>>4) & 0x0FFF); ADCmean[4] = ((LPC_ADC->DR[4]>>4) & 0x0FFF); ADCbusyflag = 1; }

What I'm I missing?

Re: ADC Burst?

Alice_Yang — Wed, 08 Sep 2021 02:54:37 GMT

Hello bmildh,

Have you test whether it works well when without burst mode?

And confirm connect to the right pin to ADC signal.

Alice

Re: ADC Burst?

bmildh — Wed, 08 Sep 2021 05:17:31 GMT

Aey, It works in software mode. I use one channel at a time with interrupt. In the ISR I read the adc value for the current channel, then I setup the adc for the next channel. I can then start the timer at arbitrary time intervals (like, 1ms, 10ms or whatever).

Re: ADC Burst?

Alice_Yang — Thu, 09 Sep 2021 02:17:16 GMT

Hello,

How about just enable channel 7 interrupt?

If still can't work, you can attach your project, I will check it on my side.

Alice

Re: ADC Burst?

bmildh — Thu, 09 Sep 2021 06:27:52 GMT

I tried just enabling channel 7 interrupt, but no dice.

Anyway, I'll figure It out, probably just some bit in some register that is wrong. It usually is

Thanks for the help.

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