nrf905 query: different frequnecy of crystal oscillators can be used - does this affect transmission frequency

[AJF_Nordic]

I am using the nrf905 in a project. The datasheet suggests crystals of 4mhz, 8mhz, 12mhz, 16mhz and 20mhz are all acceptable. Does the choice of crystal oscillator frequency affect the RF frequency on which the 905 transmits and receives?  The formula for calculating the RF frequency suggests that only the CH_NO (channel) and HFREQ_PLL settings in the RF_CONFIG register affect the transmit/receive frequency.

Is it true that the crystal oscillator frequency does not affect the RF frequency and that the nrf905 does not need to be "told" what the external crystal's frequency is?

(Also, is the nrf905 still considered a current part that should be chosen for new designs, or is it nearing obsolecence?)

THANK YOU IN ADVANCE!

[ketiljo]

You must set the crystal frequency on the XOF register. The default is 16 MHz. See the product specification, page 24. Then RF frequency will be according to the CH_NO setting.

The nRF905 is still a current part.

[AJF_Nordic]

Hello,

Thanks for the reply. I'd become so immersed in the rest of the firmware that I'd forgotten about the XOF bits to set the crystal frequency. However checking my firmware I can see that some time ago I had set them correctly for my 16mhz crystal.

Thanks again,
Andrew