BLE4.0 TX frequency

[wiki]

Hello NORDIC

We found that TX frequency error is quite large. Is it able to compensate TX frequency by software ?

[RK]

Are you running a softdevice? Those registers are part of the RADIO module so you can't access them. So they're no use to you and you have to fix the crystal oscillator. Have you read the Crystal Oscillator White Paper which explain this?

[RK]

I've said what I think about it twice now, you can't do it. Trim registers do exist which possibly allow TX frequency trimming for proprietary uses of the radio, however they are both relatively undocumented and, more importantly, they are part of the RADIO module. When using a softdevice the RADIO module is restricted, the softdevice owns it, you are not allowed to access any of the registers.

As John DeWitt points out above, the manual strongly suggests that the trim registers are likely loaded with the factory calibrated values from the FICR when the softdevice is started, and once it's started, you have no access to them.

Nordic provides no radio API point I can find which allows you to change those, or adjust the TX frequency in any way so I can see no provided way for you to do this.