Firstly I want to give a huge thanks to Paul Archer. In my day job my employer has signs everywhere that say “Verify your design inputs”, and to that end we have a process of independent verification for everything. Paul has been that sounding board and verifier in the last couple of weeks, and without him I could have spent a lot more time dealing with issues of this board. I won’t say it’s perfect but it should work well.
I’m using a Texas instruments reference design for an PIFA style antenna that’s been extended. I plan to tune it with a 2.4GHz spectrum analyser by measuring power output. I’ve seen this technique several times.
I’ve realized today while checking footprints that very small components will have a “drop factor”. Essentially, 0402 parts and the BAL-nRF1D03 components will be hard to hold and align. So much so that I suspect that I will need a 3:1 ratio. Drop 2 – 3 and get one installed.
I do like the Purple boards. I’ll likely do a trace antenna design this week and also have it made in case the PIFA doesn’t work out. I am having trouble though making sure that I have the correct impedance match for a trace. Seems 1.6mm FR4 would require 2.81mm wide trace in 1oz copper according to the calculators, but most designs I’ve seen are much narrower. I’m not 100% sure who to trust. Antenna’s still feel like black magic thus far.
There is a 10 pin expansion header with 7 GPIO outputs that can be configured to any type of communications bus in addition to the 10 pin SWD programmer header. It has built in RTD sensor inputs for never having to zero your power meter. An RTD is a temperature sensor, and this will be used to measure each strain gauge setup. This is similar to Rotor Power. This won’t be fully implemented initially as it’ll require calibration for every power meter and I will have to sort that process but it will be.