Combined NFC reader / keypad

RE: Combined NFC reader / keypad

Fred27 — Tue, 13 Nov 2018 19:48:35 GMT

The capacitive touch keypad is also working pretty well, including decoding key presses and checking for the right code. The proximity / guard sensor works, but may need some tuning so I've disabled it for now.

[View:https://players.brightcove.net/1362235890001/NkxiVJdjx_default/index.html?videoId=5966491784001:740:466]

Unfortunately, the 10mm mutual capacitive sensor buttons work just fine for me but seem to have a bit of trouble detecting my 4-year-old's tiny little fingers and it is really meant for him to use. Not sure if tuning will sort this out or if a redesign of the key is in order.

RE: Combined NFC reader / keypad

Fred27 — Sat, 27 Oct 2018 20:20:16 GMT

Thanks for the advice about bodging in another crystal. I did that, adapted some basic NFC reading code and what do you know - it works! [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-88ef04f6-7ecb-4c1b-a66f-1fa80415e451/contentimage_5F00_938.png:16:16] Despite my questionable QFN soldering and guesswork at antenna tuning it actually reads my implanted NFC tag. I'm still always surprised when something works. I think the range / sensitivity could be better but I'm happy for now. I'll leave the capacitive touch keypad for another day.

[View:https://players.brightcove.net/1362235890001/NkxiVJdjx_default/index.html?videoId=5854330184001:740:466]

RE: Combined NFC reader / keypad

luislabmo — Fri, 26 Oct 2018 11:45:55 GMT

Hi Fred,

It's looking good. Looking forward to more updates.

Luis

RE: Combined NFC reader / keypad

BigG — Fri, 26 Oct 2018 10:14:55 GMT

I love the inclusion of the NFC antenna.

Did you refer to any design guides to make this. What trace width did you use, for example.

I'm very much a noob here, so was wondering how did you "tune" that antenna, as in choose the correct resistor & capacitance values for the antenna.

RE: Combined NFC reader / keypad

Fred27 — Fri, 26 Oct 2018 08:24:29 GMT

Thanks for the offers, guys. I'm sure I've probably also got some old crystals lying around somewhere that could be bodged in. However, I've also got other things to take a look at right now - such as continuing with the FPGA stuff.

I've email Farnell to ask if they could swap in an alternative component. It's frustrating when you pick one because it's in stock but by the time the order goes through it's out of stock and there's another pretty much identical one with thousands available.

The solder really isn't that good up close!

RE: Combined NFC reader / keypad

Gough Lui — Thu, 25 Oct 2018 22:40:03 GMT

I wonder if you have any old wristwatches which might be out of battery which you could cannibalise the 32.768k crystal from? Just a thought ... as I recently did the same [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-88ef04f6-7ecb-4c1b-a66f-1fa80415e451/contentimage_5F00_1.png:16:16]

- Gough

RE: Combined NFC reader / keypad

genebren — Thu, 25 Oct 2018 22:04:15 GMT

Fred,

I don't know if it will help you, but I do have a number of 32.768 crystals that I could send to you. They are old stock, in either cylindrical can or low profile HC-49 (?). I can get you part numbers, once I dig them out of storage.

Let me know if they can help you.

Gene

RE: Combined NFC reader / keypad

shabaz — Thu, 25 Oct 2018 21:47:12 GMT

This looks really great!! The soldering looks good too!

How long did it take for the boards to be manufactured and arrive?