ADC result not changing

RE: ADC result not changing

MARTIN FR — Wed, 17 Feb 2016 15:04:15 GMT

Hello brian, are you testing your battery votlage via USB or cr2032 battery? because for USB 2.89volt as VDD and cr2032 2.62 VDD i measured in the DK you also getting the same kind of result?

RE: ADC result not changing

karan — Wed, 17 Feb 2016 15:02:21 GMT

Could you share me some piece of detailed inofrmation about how you verfied your abttery voltage in the analog pin 5 ?

RE: ADC result not changing

Brian — Wed, 17 Feb 2016 14:57:46 GMT

Hi Prabhudurai, Yes, I am getting the correct battery voltage once I made the change that Stefan suggested.

RE: ADC result not changing

MARTIN FR — Tue, 16 Feb 2016 08:31:08 GMT

Hello Brian could you please tell me whether you got the correct battery voltage reading with this program? because am facing similar kind of issue with the ADC so your ideas or suggestion would be helpful for me to proceed further

RE: ADC result not changing

Brian — Wed, 14 Oct 2015 20:26:41 GMT

Hi Stefan,

That was definitely the issue. Thanks! I'm now getting the expected readings with different voltages on the input. Good catch!

RE: ADC result not changing

Brian — Wed, 14 Oct 2015 15:47:00 GMT

Hi Stefan,

I am configuring the ADC after the softdevice is configured. The ADC configuration is one of the last things I do in my initialization. Also, the values I've seen from the ADC result are 0xCA, 0xCB, or 0xCC - so it does actually change values. Here is a register dump of the ADC registers right after the ADC_IRQHandler reads the ADC result:

0x40007500 00000001 00002018 000000CC 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 ..... ..Ì....................................... 0x40007530 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 ................................................ 0x40007560 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 ................................................ 0x40007590 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 ................................................

Also, I have verified with a scope that I have 0V on P0.04 when connected to GND and I read ~0xCC from the ADC. I've also verified that when I connect P0.04 to VDD, I have 2.84V on P0.04 and I still read ~0xCC. It also seems like P0.04 is not mapped to AIN5. Is it possible for this mapping to be changed to a different port pin?

And here is my main function. I have tried removing all of the non-Nordic initialization other than the ADC initialization, but I get the same results.

int main(void) { uint32_t ticks; uint32_t err_code; bool erase_bonds; uint32_t var1; uint32_t var2;

// Initialize.
timers_init();
gpio_init();
uart_init();
system_tick_init();
buttons_leds_init(&erase_bonds);
button_init();
ls_init();
ble_stack_init();
device_manager_init(erase_bonds);
nvm_init();
gap_params_init();

// Comment out the next line to enable single-step debugging
//advertising_init();

services_init();
//sensor_simulator_init();
conn_params_init();

// Start execution.
application_timers_start();
system_tick_start();
err_code = ble_advertising_start(BLE_ADV_MODE_FAST);
APP_ERROR_CHECK(err_code);

app_timer_cnt_get(&ticks);
printf("%"PRIu32": Starting Nordic Strobe\r\n", ticks);


var1 = nvm_read(NVM_mode);
app_timer_cnt_get(&ticks);
printf("%"PRIu32": NVM_mode = %"PRIu32"\r\n", ticks, var1);

var2 = nvm_read(NVM_speed);
app_timer_cnt_get(&ticks);
printf("%"PRIu32": NVM_speed = %"PRIu32"\r\n", ticks, var2);

for(int i=GPIO_LED1; i<=GPIO_LED4; ++i)
{
    gpio_write(i, GPIO_ACTIVE);
    nrf_delay_ms(100);
}

for(int i=GPIO_LED1; i<=GPIO_LED4; ++i)
{
    gpio_write(i, GPIO_INACTIVE);
    nrf_delay_ms(100);
}

uint8_t battery_levels = display_init();
battery_init(battery_levels);
ls_start();
fsm_init();

// Enter main loop.
for (;;)
{
    // Run the state machine if it's time to
    if (fsm_get_ready())
    {
        fsm_run();
    }

    // Flush NVM if it's time to
    if (nvm_flush_ready())
    {
        nvm_update();
    }

    // If we've advanced past displaying the logo, then...
    if (fsm_get_state() > FSM_STATE_LOGO_DONE)
    {
        // Update the battery level display if it's changed
        if (battery_level_changed())
        {
            display_battery(battery_get_level());
        }
    }
}

}

RE: ADC result not changing

Stefan Birnir Sverrisson — Wed, 14 Oct 2015 12:41:00 GMT

Hi Brian

First hint: Make sure you configure the ADC after you initialize the softdevice.

Perhaps this link could be relevant for further hints.

Just to verify my understanding of the problem, do you always see 0xCC value from the ADC when a breakpoint is hit in the ADC handler?

Update 14.10.2015

I see the error now. Instead of writing

adc_config.scaling    = NRF_ADC_CONFIG_SCALING_SUPPLY_ONE_THIRD;

you should write

adc_config.scaling    = NRF_ADC_CONFIG_SCALING_INPUT_ONE_THIRD;

That will make the ADC sample from an analog input pin. With your current configuration, you are sampling the supply voltage of the chip.