CC2640R2F: XOSC Cap Array / Crystal Tuning

Hello JXS & Fredrick,

Thanks for the feedback, I do remember the recommendation from last fall. I sent it along to the appropriate parties and the decision was still made to move forward with developing the calibration procedure. I'll renew that discussion to make sure we are not going down the wrong path.

In the meantime, I will look into what you mentioned with the driverLib functions JXS, glad to hear there is a path forward if it's needed. If I get tripped up on the implementation I will report back.

Fredrick, I don't have access to our customer's PDM system to pull the full crystal part numbers, but I believe we are using the:
AVX / Kyocera Cx3225GB24000 with the R2F and (8 pf load capacitance versions) and
AVX / Kyocera Cx3225GB48000 with the CC2642

We will be opting for use of the CC2642, assuming that production parts are available when we are ready to release our product to production.

Thanks,
Josh

Fredrick, I haven't had access to enough boards to do testing on a significant sample, but on the 10 R2F boards I was able to test with a fixed 7.6pF load cap value all boards were within +/- 12 KHz of the target carrier frequency. Most were closer, but there were outliers at +12 and -12 KHz.

After some more discussion with my customer we've concluded that this calibration is no longer a hard requirement, there was some confusion on the Radio Frequency tolerance for BLE. We may pursue it anyway as there will already be a station on the manufacturing line with the equipment needed for some other conformance testing. In theory from the calculations we've done, a product could still eventually drift out of spec after ~9 years, if it were a worst case outlier when initially manufactured.

JXS, thanks for the advice on the driverLib calls. It was pretty easy to get dynamic load cap array changes integrated into our application. I went a slightly different route than you outlined, as the CC26X2 SDK 1.60 driverLib provides a specific API for modifying this value (I'm guessing this was added for the feature added to the SmartRF Studio 7 GUI).

For anyone curious, here is how I implemented it. When I receive an updated Cap Array value on our products CLI I do the following:

                    Log(LOG_CONSOLE_LEVEL, "Updating cap array delta to %d\n", delta);
                    uint32_t key = Hwi_disable();
                    NOROM_OSC_AdjustXoscHfCapArray(delta);
                    NOROM_OSCHF_SwitchToRcOscTurnOffXosc();
                    NOROM_OSCHF_TurnOnXosc();
                    while (!NOROM_OSCHF_AttemptToSwitchToXosc()) {}
                    Hwi_restore(key);

Thanks for the help, I think I'm all good on this topic!