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Populated Lock NFC boardSo, after waiting for the PCB to arrive from Seed, it was time to populate it, run it through the toaster oven and see if I'd made any mistakes. As usual, I struggled a bit with the QFN soldering of the TRF7970A NFC transceiver. I can never seem to get these right without using solder paste, then slapping on too much solder with a soldering iron and then wicking it away. I can take a few goes, but I seem to get there in the end. The final result looks professional enough with the naked eye even if the process certainly wasn't. Give me QFP over QFN any day!


You can't really test the hardware without some firmware running on the microcontroller, so I quickly adapted my test code from the development board. It wasn't too long until I had the capacitive touch button code running and working. Then I got the NFC code reading an NFC tag. I've yet to combine the two lots of code properly, other that to ensure they fit in the flash of the MSP430FR2633. The demo makes it look a lot more finished than it is. I wasn't too happy with is the sensitivity of the buttons. They seemed a bit too sensitive when I used it and would often register a double press. However, when my kids tried it had trouble detecting their little fingers. The NFC antenna certainly worked and I was pleasantly surprised for a first attempt, but I was sure it could be better. I was really pleased that the reverse mount LED diffuses nicely through the PCB. I suspect that if I have another next to it that I would get light bleed between them, but as I've only got one it works really well.



I don't know why I'm still surprised when a board that I've designed works, but I still am - every time.

Next post - Antenna tuning >>