Why NRF24LE1 ADC is reading value always as 255?

[infibit]

I am doing a register retention gzll transmit code with ADC. But problem is that the ADC value transmitted is always 255, if I connect ground to ADC it would read 247. Why is there such a problem here. Here is my code:

#include"reg24le1.h" // I/O header file for NRF24LE1
//#include"hal_uart.h" // library containing serial communication functions
#include"hal_delay.h" // header file containing delay functions
#include"hal_clk.h"
#include <stdio.h>
#include "nrf24le1.h"
#include "gzll_mcu.h"
#include "gzll.h"
#include "hal_adc.h"

// Repeated putchar to print a string
/*void putstring(char *s)
{
  while(*s != 0)
     hal_uart_putchar(*s++);
}*/
 int gzlinit=0,val=0;
 uint8_t payload[3];
 void wakeup_irq() interrupt INTERRUPT_WUOPIRQ
{
	;//putstring("Hello Ranjan I woke up\n");
	//gzlinit=1;
}
// main function
void main()
{
	//hal_clklf_set_source(HAL_CLKLF_XOSC16M_SYNTH);
	//hal_clk_set_input(HAL_CLK_XOSC16_OR_RCOSC16);
	 mcu_init();
  gzll_init();
	
	//hal_clk_set_freq(HAL_CLK_125KHZ); //if you put in 125Khz then uart wont work
		WUOPC0 = 0x02;

P01 = 0x00;
P1 = 0x00;
P2 = 0x00;
P3 = 0x00;

P0DIR = 0x02;
//P0DIR = 0xf2;//0x02 only for pin wake up 0xF2 both for uart and pin wake up
P1DIR = 0x00;
P2DIR = 0x00;
P3DIR = 0x00;


// Initializes the UART
 // hal_uart_init(UART_BAUD_9K6);
 hal_adc_set_input_channel(HAL_ADC_INP_AIN6);
  hal_adc_set_reference(HAL_ADC_REF_VDD);
  hal_adc_set_input_mode(HAL_ADC_SINGLE);
  hal_adc_set_conversion_mode(HAL_ADC_CONTINOUS);
	//hal_adc_set_conversion_mode(HAL_ADC_SINGLE_STEP);
  hal_adc_set_sampling_rate(HAL_ADC_2KSPS);
  hal_adc_set_resolution(HAL_ADC_RES_8BIT);
  hal_adc_set_data_just(HAL_ADC_JUST_RIGHT);
// Enable global interrupts
	IEN1 = 0x08;
  EA = 1;
	//MISC=1;
	hal_adc_start();
	PWRDWN = 0x04;
			// Clear power down
	PWRDWN = 0x00;
 //putstring("\r\nHello Init!!\r\n") ;
// delay_ms(2000);
  
//infinite loop
while(1)
{
// Print "Hello Everyone"
//putstring("\r\nHello Everyone!!\r\n") ;
//delay_ms(1000); // delay of 1sec
	
	while(P01==1)
		{
			//if(gzlinit==0)
			{
				PWRDWN=0x07;
			//gzll_init();
  
		
    if(gzll_get_state() == GZLL_IDLE)
    {
			while( hal_adc_busy() )                         // Wait for the ADC to finish a conversion
    {
		}
			val = hal_adc_read_LSB();
      payload[0] = val;
      // Transmits payload[] to pipe 0 address
      gzll_tx_data(payload, 3, 0);
      //gzlinit=2;			
    }	
			gzll_goto_idle();
	
			//putstring("\r\nHello Everyone!!\r\n") ;
			//if(gzlinit==2)
	    //break;
		}
	}
		gzlinit=0;
		// Register retention mode
			PWRDWN = 0x04;
			// Clear power down
			PWRDWN = 0x00;
	}
}

[infibit]

Dear Support Engineer, I am waiting for your reply.

[Kenneth]

Have you set the HAL_ADC_INP_AIN6 pin as input? 

Best regards,
Kenneth

[infibit]

Does this code of line  hal_adc_set_input_channel(HAL_ADC_INP_AIN6); not do that?  So how do we set a pin as input? (Also at the same time let me know how to set it as output? Say P0DIR =0 and P01 = 0 set it as output?). Since the pin wake up on port 0 needs P0DIR = 0x02, on the same lines P0DIR=0x22 will set AIN6 also as input?

[infibit]

Even after declaring P0DIR as 0x22, I am still getting the same problem. ADC reads 255 and if I ground it instead of reading 0 it reads 247.

[Kenneth]

I recommend to try the SDK example: \nRFgo SDK 2.3.0.10040\source_code\projects\nrfgo_sdk\adc_examples\adc_single_step_mode 

You should only need to modify: hal_adc_set_input_channel(HAL_ADC_INP_AIN0);