adc using sdk example didn't give the right value

RE: adc using sdk example didn't give the right value

acha — Wed, 04 Jan 2017 16:14:15 GMT

Ah! that's was the problem, I applied a tension between 0 and 5V (~4.38V) instead of 0 ~ 3.3V. Now it's better ;)

RE: adc using sdk example didn't give the right value

Jørgen Holmefjord — Wed, 04 Jan 2017 15:27:25 GMT

Input voltage of 0 should give a result of ~0. Are you sure this is what you are applying? What is the operating voltage (VDD) of your nRF IC? The input range of the SAADC should be from 0 to VDD.

RE: adc using sdk example didn't give the right value

acha — Wed, 04 Jan 2017 15:07:38 GMT

thanks you for your answer, i tought that the function takes the number of of AINx. However, when my input voltage vary from 0 to 4.38V, the resulting value of adc increase to 899 and then decrease to 512. I dont understand why ? :O

RE: adc using sdk example didn't give the right value

Jørgen Holmefjord — Wed, 04 Jan 2017 15:00:52 GMT

Hi,

You say you "set an input voltage in varying from 0 to 4.38 V in the pin 4 (AIN2)", but in your code you initialize the channel with nrf_drv_saadc_gpio_to_ain(2). The SAADC channel will then be on GPIO pin 2 (AIN0). If you want to use AIN2 (pin 4), you should initialize the channel using nrf_drv_saadc_gpio_to_ain(4). You can also use the defines NRF_SAADC_INPUT_AIN0 to NRF_SAADC_INPUT_AIN7 directly.

Best regards,

Jørgen