BLE4.0 TX frequency

RE: BLE4.0 TX frequency

wiki — Mon, 16 Mar 2015 11:20:29 GMT

ok，thank you so much !

RE: BLE4.0 TX frequency

RK — Mon, 16 Mar 2015 01:29:49 GMT

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.

RE: BLE4.0 TX frequency

wiki — Mon, 16 Mar 2015 01:05:03 GMT

Yes, we are running a softdevice when we test BLE . My team menber told me that BT Tx frequency can offset by registers and we can creat a array to offset the error . What do you think about it ?

RE: BLE4.0 TX frequency

John — Fri, 13 Mar 2015 12:16:42 GMT

I agree the softdevice would likely be an issue. Plus from what you can learn from the reference manual it sounds like the registers would be loaded with factory calibration data by the softdevice. It would be better to address the tuning of the circuit.

RE: BLE4.0 TX frequency

wiki — Fri, 13 Mar 2015 06:27:15 GMT

Yes, BLE parameter can be measured by IQXel device .We hope a little frequency error can be compensated by software .

RE: BLE4.0 TX frequency

RK — Fri, 13 Mar 2015 06:23:36 GMT

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?

RE: BLE4.0 TX frequency

wiki — Fri, 13 Mar 2015 05:48:50 GMT

really？can you descript it in detail ? Which register can be set in nrf51822 ?

Thanks !

RE: BLE4.0 TX frequency

RK — Thu, 12 Mar 2015 12:26:59 GMT

I see they exist, however as the radio is marked as a blocked device when using the softdevice (and I did make the assumption here that a softdevice is in use) they're not usable, and I didn't find an API point which exposed them, I discounted being able to use those.

RE: BLE4.0 TX frequency

John — Thu, 12 Mar 2015 12:20:20 GMT

Well, there appears to be trim registers for the radio peripheral that could be used to adjust the TX frequency. Not a game I'd want to be playing though.

RE: BLE4.0 TX frequency

RK — Thu, 12 Mar 2015 04:11:49 GMT

How large? How have you measured it? Is this a reference design or your own custom board? If custom then how tuned is your crystal oscillator as that is the largest factor in TX frequency.

No you can't fix it in software.