Potential Pitfalls in HW design for NRF BLE chipsets.

[Lakerno]

Is there a summary of potential pitfalls, i.e. issues which are asked repeatedly by users in these forums regarding HW/Schematic/PCB design for NRF BLE chipsets. Making mistakes in HW design is really costly, so appreciate if we can learn from the collective experience of the community.

If you know about OR have made any posts regarding this, please post a link. Thank you!

[Michael Dietz]

Some of the big mistakes I made when I was developing with the nRF51:

I had very tight deadlines and I didn't pay any attention to actually sourcing the components I would need (nRF51 IC, clocks, caps, etc...) When the time came to order these components and ship them to my board manufacturer for soldering I realized they were out of stock (I couldn't find nRF51 rev 3 wlcsp chip, and the clocks). I ended up trying to find close matches in terms of specs and somehow managed to buy a revision 1 chip of the nRF51. Boards came in fully soldered and that's when I ran into problems :) - lesson learned - make sure that the revision of the chip you use is compatible with the version of the SDK you are developing with.

Programming/debugging your custom PCB. My PCB was required to be very small. So I didn't include a pin header for SEGGER debuggers to attach to. This ended up being a huge pain to constantly reprogram and debug with. Lesson learned: really think about including atleast a 6 pin header and if needed design it like Nordic's example beacon so you can break it off when you want to.

Another mistake I made: Take it easy with your first revision of the PCB. Don't kill yourself with size constraints -- make it easy to program and debug. The PCB design doesn't have to be PERFECT at first (or second). Expect it to change - especially if you are inexperienced here. Get a design that works good enough at first so you can start seeing the real world implications of your design choices instead of just theoretically going through them over and over again in your head while designing your PCB.

Be very careful with making custom pads! Try to use pads for your PCB design that somebody else has made and actually tested!! Even if you follow specs (i.e. a battery holder) it might not be totally correct. I followed a battery pad spec exactly and when I went to solder it to my board I realized the contacts short circuited! I had to use electrical tape to solve that problem.

My last tip: try to use Nordic's reference designs as much as possible. Read ALOT of questions here on the dev zone and look at their white papers and application notes. Think very deeply when it comes to the RF/antenna portion of the layout and grounding planes :)

Oh and dont expect it to work the first time. Have a plan of how you will test it in small incremental stages. Be smart about how you verify its working and don't just scrap & hack like i did the first time around!

Hope it helps! -Mike

[Lakerno]

helpful tips. Thanks Michael.