Is external crystal neccessary at all on 52832

[Roland]

As i am migrating to 52 and tuning the ble app, i realized by reading many posts here that:

1. external HF xtal is not recommended
2. external LF xtal can be replaced by using internal xtal with temperature compensation.

So does that mean external crystal (either HF or LF ) actually not needed at all on 52?

[Sigurd]

Hi,

1. External HF crystal is mandatory if you want to use the radio peripheral. If you are using BLE, you have to use an external 32 MHz crystal with a frequency tolerance of max 40 ppm. As mentioned in this post:

The external HF clock is critical for data timing and more critical to keep the bluetooth radio on the correct frequency. All the 2.4GHz channels are derived from the 32MHz crystal. So the ppm accuracy of the xtal will be the same ppm accuracy of your carrier in the 2.4GHz band.

2 .

External LF crystal(32 kHz)is not mandatory, but recommend. See this and this post.

Since you are migrating to nRF52832, I recommend to take a look at the General PCB design guidelines for nRF52 series tutorial

[Roland]

thanks @Sigurd and @RK for the clarifications. I may misunderstood some posts.

My custom board of 52 already made, with an external HF 32M xtal, no LF though. So i think the only way now is to use internal RC osc for SD then. So am i correct to set NRF_SDH_CLOCK_LF_XTAL_ACCURACY in sdk_config.h to NRF_CLOCK_LF_XTAL_ACCURACY_250_PPM ?

I am asking because though seems that i already made the application running on my custom board, and the advertising started (returned error code 0), but i can not find my device on central side. did not find any clue yet.