ADC Continuous read

[??]

hi,I have to question about ADC,please help me ,thank you very much!

I joined on the ADC input pin an adjustable resistance, to change the voltage value.Why change the voltage value of the ADC to read out the value of the without change

The code is as follows, please help me to find out the problem

---

main(){

	timer1_init();
	ppi_init();
	peripheral_configure();		
	nrf_adc_init(ADC_RES_8bit,ADC_INPUT_AIN0_P10,ADC_INT_DISABLED);						  
                     
                            vbat = nrf_adc_read1();
							NRF_TIMER1->TASKS_START = 1;
							while(1)
								{
								 NRF_TIMER1->TASKS_COUNT         = 1;
						  		NRF_TIMER1->TASKS_CAPTURE[0]    = 1;
									
								if(( x = nrf_adc_read()) > 1.2*vbat)
							{		
									nrf_gpio_pin_clear(dynamo_power);
									Invert();							
									nrf_delay_ms(1000);
									nrf_gpio_pin_clear(dynamo_power);
									break;

				
						}
					

}
}

#include "nrf_adc.h" #define AIN0 1

---

void nrf_adc_init(ADC_Res_t ADC_res, ADC_input_selection_t ADC_input_selection, ADC_interrupt_enabled_t ADC_interrupt_enabled) { if(ADC_input_selection <= 7) { NRF_ADC->CONFIG = ADC_res << ADC_CONFIG_RES_Pos | ADC_CONFIG_INPSEL_AnalogInputOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos | ADC_CONFIG_REFSEL_VBG << ADC_CONFIG_REFSEL_Pos | (1 << ADC_input_selection) << ADC_CONFIG_PSEL_Pos; NRF_ADC->ENABLE = 1;
if(ADC_interrupt_enabled) { NRF_ADC->INTENSET = ADC_INTENSET_END_Msk; NVIC_SetPriority(ADC_IRQn, 1); NVIC_EnableIRQ(ADC_IRQn); } } }

void nrf_adc_init_vbat(void) { NRF_ADC->CONFIG = ADC_CONFIG_RES_10bit << ADC_CONFIG_RES_Pos | ADC_CONFIG_INPSEL_SupplyOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos | ADC_CONFIG_REFSEL_VBG << ADC_CONFIG_REFSEL_Pos | ADC_CONFIG_PSEL_Disabled << ADC_CONFIG_PSEL_Pos;
NRF_ADC->ENABLE = 1; }

extern uint32_t nrf_adc_read(void) { uint32_t adc_data; // NRF_ADC->TASKS_START = 1; while(NRF_ADC->EVENTS_END == 0); NRF_ADC->EVENTS_END = 0; adc_data = NRF_ADC->RESULT;

return adc_data; }

float nrf_adc_read_vbat_f(void) { return (float)nrf_adc_read() * 3.0f * 1.2f / 1024.0f; }

uint32_t nrf_adc_read_vbat_mv(void) { // The non-optimized math is: (ADC / 1024) * 3 * 1.2 * 1000 return nrf_adc_read() * (3 * 6 * 1000 / 5) / 1024; }

extern uint32_t nrf_adc_read1(void) { uint32_t adc_data; NRF_ADC->TASKS_START = 1; while(NRF_ADC->EVENTS_END == 0); NRF_ADC->EVENTS_END = 0; adc_data = NRF_ADC->RESULT;

return adc_data; } void ppi_init(void){ NRF_PPI->CH[0].EEP = (uint32_t)(&NRF_TIMER1->EVENTS_COMPARE[0]); NRF_PPI->CH[0].TEP = (uint32_t)(&NRF_ADC->TASKS_START);

	NRF_PPI->CHEN = PPI_CHEN_CH0_Enabled << PPI_CHEN_CH0_Pos;

}

void timer1_init(void) { // Configure Timer 1 to overflow every 2 seconds. // SysClk = 16 Mhz // BITMODE = 16 bit // PRESCALER = 9 // The overflow occurs every 0xFFFF/(SysClk/2^PRESCALER). // = 65535/31250 = 2.097 sec NRF_TIMER1->BITMODE = (TIMER_BITMODE_BITMODE_16Bit << TIMER_BITMODE_BITMODE_Pos); NRF_TIMER1->PRESCALER = 9; NRF_TIMER1->SHORTS = (TIMER_SHORTS_COMPARE0_CLEAR_Enabled << TIMER_SHORTS_COMPARE0_CLEAR_Pos);

// Trigger interrupt for compare[0] event.
NRF_TIMER1->MODE        = TIMER_MODE_MODE_Timer;
NRF_TIMER1->CC[0]       = 1;  // Match at even number of seconds

}

I'm sorry, because of the format problem, let you look very pain!

[Stefan Birnir Sverrisson]

Hi

There are some basic ADC examples available here.

In nRF5 SDK there is an adc example that demonstrates a simple example using the latest adc driver, it should work out of the box.

The nRF51 ADC is not so happy about high impedance on the analog input. Connecting a resistor in series to alter the voltage on the analog input pin will generate both ADC offset and gain error. This is explained on these threads (1) (2)

[??]

HI Stefan Birnir Sverrisson Thank you very much reply,I am study your method!But I will also meet problems, want to leave your mailbox,I want to give you send mail to communicate!

[??]

HI Stefan Birnir Sverrisson ，Please help me to solve one question，thank you！

nrf_adc_input_select(NRF_ADC_CONFIG_INPUT_2); The inside of the code NRF_ADC_CONFIG_INPUT_2 -----》》 NRF_ADC_CONFIG_INPUT_2 = ADC_CONFIG_PSEL_AnalogInput2, /**< Input 2. */ Corresponding physical pin is p0.02 chip？Or other foot?Can I change?How is the configuration?

[Stefan Birnir Sverrisson]

The analog pins are fixed to certain pins, see the nRF51822 PS 3.2, section 2.2. AIN2 input is pin P0.01. There are 8 analog (AIN) pins available that you can use for the ADC.