Inconsistent ADC Behaviour with DFU

[eyigiter]

Hi all,

I have a working ADC implementation (S130 + Application) and use it to measure an analog input continuously.

However if I use the same code on top of bootloader (S130+DFU+Application), it starts acting weird. When I check the ADC values, I noticed that they are fluctuating in a large margin. What may cause this issue when I use the code with DFU but works as expected without DFU code?

Regards

[Jørgen Holmefjord]

Could you elaborate on your statement "are fluctuating in a large margin"? How is the ADC setup, and what sample rate are you running at? Is the issue only with DFU, or also with other BLE activity?

[eyigiter]

Following is my ADC setup:

nrf_gpio_cfg_input(NRF_ADC_CONFIG_INPUT_2,NRF_GPIO_PIN_NOPULL);

adc_channel_config.config.config.reference = NRF_ADC_CONFIG_REF_SUPPLY_ONE_THIRD
adc_channel_config.config.config.input = NRF_ADC_CONFIG_SCALING_INPUT_ONE_THIRD;
adc_channel_config.config.config.ain = NRF_ADC_CONFIG_INPUT_2;

nrf_drv_adc_channel_enable(&adc_channel_config);

I am getting ADC samples at every 1ms. The issue occurs only if DFU is programmed to the chip. (S130+DFU+Application) By the way, you can see the waveform of NRF_ADC_CONFIG_INPUT_2 once the ADC is enabled where it is stable until ADC started.

link text

[eyigiter]

An additional information: Problem is solved if I connect the analog circuit to NRF_ADC_CONFIG_INPUT_4 instead of NRF_ADC_CONFIG_INPUT_2. So the problem looks related to AIN2 when chip has DFU code. I am still looking for a solution :(

[Jørgen Holmefjord]

Which SDK version and DFU transport are you using?

[eyigiter]

Hi Jorgen,

It is bootloader_secure in SDK_12.1.0 and I am using NRF Toolbox to transport the PKG.