Not connected pins

[Jakob]

Hi,

i have a general quastion about ANT and XC pins. Wenn i do not need BLe cann i let these pins not connected?

Jakob

[Sigurd]

Hi,

If you don’t use BLE, and don’t use the RADIO peripheral for anything else, then you don’t need to connect the ANT pin.

On the nRF51 the XC pins are used for the external 16 MHz crystal oscillator. This crystal is required when using either the RADIO, ADC or the TEMP peripheral. It is also needed in order to calibrate the internal 32 kHz RC oscillator. The internal RC oscillator has a frequency tolerance typ 1% (=10 000 ppm), this means that it will drift 14.4min per day when it’s not calibrated by the 16 MHz crystal oscillator. If this is acceptable in your application, then you can leave the XC pins not connected.

[Jakob]

Hi, Hmm, you mean if i need ADC in my application i have to use crystal oscillator? Why i can´t use ´the 16 RC -Clock?

[Sigurd]

Yes, you are right, you can use the 16 MHz RC clock, I was reading in PS chapter 8.3 that ADC “Requires HFCLK XOSC”, but that was only required to get the stated ADC accuracy in chapter 8.12. Sorry for the confusion.