NFC reader for the xNT (part one)

I’ve had my xNT NFC implant for a few months now and I’m very happy with it. The main thing I’ve used it for is opening my garage door. It was great to use it with an existing piece of commercial kit and get used to it, but I always wanted to build some custom things to use with it.

Some NFC readers

Some NFC readers.

The simplest way to get started was to find an existing NFC reader that I can interface with a microcontroller. A scratch-built reader will come in time, but for now this is the first step. I tried a few reasonably cheap NFC readers hoping that I’d find a gem amongst them. The ones that I tried are shown. There’s the (red) DLP Design DLP-7970ABP booster pack for the MSP430. This suits me as I’m a MSP430 user and may well use the TRF7970A to base my custom reader on. Next is the (blue) RC522 based reader I found on eBay. This was chosen just because the RC522 is a commonly used chip so there’s lots of sample code out there. Third the (green) YHY502. This is just something I found on eBay from China sorting by price. Lastly the (black) ID20-MFIA. I chose this as I’ve used the company’s ID-20 125kHz reader.

OK – so if you’ve stuck with me this far you will probably want to know how they fared! To be honest they were all fairly similar. They all required the implant to be right over the PCB antenna trace (not in the centre). The alignment had to be right so without rotating my hand or the reader it worked along two sides of the trace. Whilst the ID20-MFIA didn’t have a visible trace it behaved similarly. It was also more of a pain to use too. I tried to get a quantitative measurement of range but it was tricky. They could all just about read through a piece of 3mm acrylic. Just. In practice you would want to be closer than that. Ideally with as little as possible between you and the PCB. Not as good as I’d hoped.

However, two things give me hope that we can do better. Firstly, my Samsung Ezon SHS-2320 lock seems better than that. I generally place my implant right against the reader but it seems to read well and consistently. I’ll have to do a teardown soon.

Secondly there was this post by Mathieu Stephan on Hackaday. As you can see Mathieu’s made far more progress than me. He was also happy to share his results, including schematics and the values that worked for tuning his antenna. What an awesome guy.

Mathieu’s work on inductor-based readers got me poking around a bit and I stumbled over this ferrite antenna also from DLP Design. Whilst I intend to etch some boards and try out Mathieu’s design, I’m fairly time-constrained by two young sons. I thought it’d be worth seeing if this off the shelf antenna would do the trick.

Adding u.FL connector

Adding u.FL connector

Cutting PCB trace

Cutting PCB trace


There were a couple of things I needed to do to get this working. I had to cut the trace to the PCB antenna on the rear of the board. It’s a 4-layer board so lucky it wan’t on an internal layer. I also had to add the unpopulated SMT u.FL connector to the board (marked CN1).

DLP 7970ABP and FANT

DLP 7970ABP and FANT

Finally one cheap eBay u.FL to SMA (note not RP-SMA) cable and we’re sorted! So – how did it perform? Not too bad.

I don’t think it was ever possible to get a huge read range, but it’s definitely better. It will now just read through 5mm of acrylic and whilst it still operates better if oriented correctly with the implant it’s not quite as fussy. It’s a worthwhile improvement and if you’re making your own board it would definitely be worth basing it on a coil rather than PCB antenna.

There are some differences between the DLP’s and Mathieu’s designs. There’s still the Ezon to take apart. So I’ll keep going in my search for the perfect reader. Also, it might still be possible that the right (i.e. smaller) PCB trace is even better. I’m also working on the code for my first xNT project, so stay tuned…

Adding wireless charging to the Nook Glowlight

A while ago when Barnes & Noble put the Nook Simple Touch on sale I got one – thinking that for £30 then at the very least I’d rip it open and use the eInk screen for something geeky. I ended up liking it and actually using it for reading books. I liked it even more when I found it was possible to add wireless charging.

Easier connection points on the Nook Simple Touch

Easier connection points for the Nook Simple Touch

I was very impressed with Tom’s original work. I did manage to make a slight improvement by finding some easier points on the PCB to connect to – a couple of test points marked T292 and T334 on the more accessible side. You can see these connections on the photo.

When the new Nook Glowlight came out I thought it was time for an upgrade, but I’d really miss that wireless charging. Well I’ve got some good news for you. It’s possible! Not only that, but I’d say it’s probably easier to do. We still use the same Galaxy S3 wireless charging pad. Mine was £3 shipped from China by and I had no problems. I bought from befdi but there are many other sellers that I’m sure are fine too.

Disconnect the battery

Ease open the case. No screws, just clips.

Open up that case. There’s no SD card to remove or screws holding it together. Just take the rubber trim off and you’ll see some small white tabs holding the back on. I found that flipping it over and applying some gentle pressure for a small screwdriver or even a butter knife made it easy to take off. There are 2 top and bottom and three on each side. As you can see them from the front they’re easy to pop open without breaking or marking your new Nook.

Disconnect the battery

Disconnect the battery

Then open it up like a book. You’ll probably want to disconnect the battery as a precaution, but that’s all the disassembly you’ll need to do. Whilst working out what to do, I disconnected the display (just pop the connector up off the PCB), unscrewed it (6 x T6 screws) removed the PCB and disconnected the ribbon cable for the IR touchscreen, All of these turned out to be completely unnecessary but I liked to have a good look around anyway. No warranty-voiding stickers need be removed.

Locate these test points on the PCB

Locate these test points on the PCB

Whilst the PCB on the Glowlight is far more densely packed than the Simple Touch, and some of the test points are absolutely tiny, this modification turned out not to be as difficult as expected. The only points you need to access are reasonably large and marked GND and V-BUS. They’re on the more accessible side of the PCB even though the USB connector is on the other. Dab a little solder on to tin these test points, tin your wires and solder them together. Pre-tinning both means you transfer less heat to the board.

Note the polarity

Note the polarity

Now it’s time to connect to the charging pad. Note the polarity of the connection from the photo. Maybe measure yours with a multimeter just to be sure. I found when soldering that the two gold pads to connect to the phone completely came off. It’s easier with these out of the way so don’t worry. Be careful with the heat though. The pad seemed like it would melt fairly easily.

Pad facing the wrong way

Pad facing the wrong way

Unfortunately my first attempt at locating the Qi charging pad didn’t work. I positioned the pad as shown with the connectors facing away from the Nook and towards the charger. I figured there would be less chance of a short. Placing it on my Nokia charging pad did nothing. I was relieved that the Nook and USB charging was unaffected. It turns out that it won’t charge unless the “Wireless Charger” logo faces the Qi charger. I measured the output voltage both ways up and if it’s the wrong way you get nothing at all. I was surprised but that’s how it was. To be honest I hadn’t thought of this when I modified the Simple Touch. Just luck that it was the right way round I suppose.

The right way round this time

The right way round this time

My second attempt flips the pad around and so has the connectors nearer the PCB. Whilst these shouldn’t actually short anything because they’re a little about the PCB, cover them with a bit of tape anyway,.

Well – that’s it! Pop the case back on and you’re done. £3 for the receiver and maybe 15 minutes work and you now have a wireless charging Nook Glowlight. Apart from a couple of tiny blobs of solder on the PCB and a small cutout from the webbing on the back case your device is unmarked. You’d never know from the outside and could probably remove it if you ever needed to return it under warranty and nobody would notice. Your warranty is void though. You know that, right?

Freewheeling Friday

What a totally random Friday I just had. If you’re a fan of Ross Noble then you might have seen his series Freewheeling where he responds to random stuff on Twitter and heads off round the country on his motorbike. Well, he’s currently busy filming for series 2 and when he tweeted this I thought I’d mention my NFC implant.

I am looking to feature the following on freewheeling.
Ventriloquism
Taxidermy
Alternative people(tattoos body mods etc)
Can u help

The film crew in my garden

The film crew in my garden

A few messages back and forth with his production team and he turns up with a film crew to have a chat. We spent about 20 minutes or so in my back garden chatting about the back door to my garage / workshop which has an NFC-enabled lock. My wife also had a chat about how she wanted nothing to do with implanting it for me. She pretended to be all aloof about having a celebrity popping round, but when it looked like she’d be out before they turned up, she managed to cancel her other engagement!

Me, and a firmly shut garage door

Me, and a firmly shut garage door

I also showed him the Fisher Price records and the laser. We chatted for a bit about motorbikes while the crew sorted out the next destination – a taxidemist who stuff mice in positions reading the newspaper, etc.

Adam (two and a half) was too shy to join us.

Adam (two and a half) was too shy to join us.

He seemed to be a really nice genuine guy. And whilst it looks like a bit of fun it seems like really hard work to make it look that way. They do 2 weeks solid filming morning to night 3 times. Each week turns out to be a single episode. My older boy Adam is motorbike obsessed and loved his KTM SuperDuke. Ross even said he could sit on the bike, but a bout of shyness meant that he wouldn’t.

All in all, a fairly unusual day. Then off for a stag weekend…

Oh yeah – it should be on around the end of the year. I’ve no idea how much footage they take or how likely I am to make the final cut. It’s a great series though. Watch it anyway.

CNC controller enclosure

Laser cut acrylic enclosure

Laser cut acrylic enclosure

I converted my Proxxon MF70 mill to CNC quite a while ago. When I was testing things out I wired up the PSU and controller board and just threw them in a Tupperware container so that nobody got electrocuted. It even had the lid open to allow the cables (including 240V mains supply) in. A temporary hack if ever there was one. You know how temporary hacks are though – they tend to stick around longer than intended.

Close up of the connectors for the axes, e-stop and LED

Close up of the connectors for the axes, e-stop and LED

Well, I finally got round to making a proper acrylic enclosure. I attempted to mill one ages ago, but struggled with the small working area on the MF70 and abandoned it. This one is laser cut. It’s held together with machine screw’s and has two shelves – one for the PSU and one for the TB6560 based stepper controller. I particularly like the rounded piece for the power LED and the hexagonal grid for venting.

I’d be happy to share the design files if anyone is interested, but I doubt anyone has exactly the same setup as me. I also altered things as I went, so I don’t have any “final” versions.

Laser improvements – coolant monitoring

One of the quickest ways to destroy a CO2 laser tube is to let it overheat. My laser has a very simple system – just a plastic breakfast cereal container of water with a small aquarium pump. It works well enough, but is easy to forget.

My first modification was to power the pump from the laser so that it’s running when the laser is switched on at the mains. That gets around the “oops, I forgot” problem, but doesn’t cover a pipe coming loose or the temperature creeping up. I really wanted to actually check cold(ish) water was flowing through the glass laser tube.

The water and temp sensor

The water and temp sensor

To check the flow, I started with a LM35DZ temperature sensor and a cheap water flow sensor from eBay. For neatness I carefully milled the flow sensor to embed the temperature sensor in it. This was then attached to the output of the laser. I intend to check that enough water is coming out and that it’s below a temperature threshold.

I etched a board with a MSP430G2533 microcontroller that counted the pulses from the flow sensor over a fixed timer period and used the onboard ADC to read the temperature. I set the threshold at 40C and 75% of the normal flow.

PCB with logic error

First PCB with logic error

My initial attempt used a MOSFET to pull the last signal down to GND if things were awry. Unfortunately this fired rather than disabled the laser! This was replaced with a 74LSxxx AND gate so I could force it to 5V and disable the active low signal. Some connectors to match the controller board meant I could drop it in with no rewiring.

The finshed PCB - with a fix for a lifted trace

The finshed PCB – with a fix for a lifted trace

So far it has been working well. (I actually finished this months ago but didn’t document it.) It’s not actually been needed to save my tube yet, but it’s nice to know it’s there. I might later and another sensor on the input and also flag if the difference between the two is too high. I could also add a cheap LCD display but that seems a little over the top.

Coolant monitor in the laser

Coolant monitor in the laser

As it’s a single sided board with some through hole pin headers, when it’s in place you only see the “boring” side of it with not tracks or components. Oh well – there’s no need for it to look pretty. Here it is in place. It’s a drop-in addition on the 6 pin cable to the controller board. It’s powered from the existing 5V line and simply forces the signal to fire the laser high (as it’s active low) when it senses trouble. From teh top you can see:
  • The connector to the sensor
  • A debugging / programming header
  • A currently unused connector for a screen
  • The connectors to patch into existing power and signals

If anyone wants a copy of the PCB layout or code, just ask.

My NFC implant

For quite a few years now I’ve wanted to get a RFID implant. The main use for one I suppose is as a key that you can’t lose. RFID readers are readily available and it’s not too hard to add a microcontroller and get it doing what ever you want. The main reason I didn’t get one is that the last few places I’ve worked (and a friend’s holiday house) have used the proprietary Paxton RFID entry system. Whilst this works using a 125kHz carrier like most standard systems, it’s deliberately incompatible with the standard EM4100/EM4200 125kHz tags that are available in implantable form. Very annoying. I did contact Paxton to see if it would be possible ot create an implantable Paxton tag, but unsurprisingly they said it wasn’t. It would be annoying having a RFID implant that I could almost use every day!

Well, everything changed when I spotted a crowdfunded campaign for a NFC based implantable tag. It was run by someone I recognised from his work with EM4200 tags – Amal Graafstra. NFC is similar, but it works using a high frequency 13.56MHz frequency. It’s pretty much high frequency RFID with a few protocols on top. The big plus is that reading NFC is supported by things like smart phones. I decided to go for it. Here it is.

It was a particularly well run campaign. (Much better that the Agent watch I’m still waiting for.) A few months later and my ready to implant tag arrived!

Ready to implant

Ready to implant

On to the next step – getting it implanted. This proved a little trickier. Some people have done it themselves and I’m not too squeamish about these things, but you really need two hands and as it’s going to be stuck into one of them, you only have one free! My wife’s a GP and would definitely be capable of doing it, but she refused. Not for any medical or ethical reason – just because she said it was “weird, geeky and creepy and if I wanted something daft like that done she wouldn’t help”. Fair enough I suppose. I went to a few piercing / tattoing studios but they all felt it was outside of what they were comfortable with. Eventually Kalima were recommended and I popped along. They were really friendly, helpful and professional. I can’t recommend them highly enough. It wasn’t cheap (£100) but I’d checked out the quality of their other work and was impressed – especially with things like ear reconstruction which must be far more complicated that this!

Anyway, with detailed instructions from Dangerous Things and Quentin’s experience with implanting neodymium magnets and stuff, it al went well. Anyway, enough of the waffle. You probably just wanted to see some gory photos!

X marks the spot

X marks the spot

In it goes

In it goes

Just checking the position is right

Just checking the position is right

A bit of bleeding

A bit of bleeding

I’m also glad to say it works really well unlocking both my Nexus 5 phone and the Samsung Ezon SHS-2320 lock on my workshop. I’ve currently got my contact vCard on it so can give my details to someone just by touching their (NFC enabled) phone against my hand. That would have been much more useful before I was married!

Further PCB improvements

I’m glad to report I’m getting even better result with my PCB etching. Results do seem a bit up and down each time I get back to it but I feel I’m narrowing it down and getting more polished.

One. I’ve started using Ziplock vacuum bags to evenly press the transparency against the PCB. A really nice cheap substitute for a vacuum light box! I can thoroughly recommend them.

Etching underway

Etching underway

Two. I’m now able to get even better exposure with 3.5 minutes under the UV box rather than using the fluorescent tube. Maybe my developer solution used to be too strong. Maybe ditching the glass in favour of the Ziplock helped. Regardless, I’m getting a really good result. Here’s the partially etched board showing great definition.

Three. I got some Tin plating solution. No idea why I didn’t do this before, as it’s really easy and gives a great finish. The instruction say to carefully clean the copper with an abrasive. However, I assumed that as I’d just removed the etch resist from the copper with acetone and it had to be just about as clean as it could be. I popped it straight in the tinning solution before I got fingerprints all over it.

Etched and soldermasked board

Etched and soldermasked board

Milled, drilled and populated

Milled, drilled and populated

I had to mess something up and I removed the protective layer on the soldermask before exposing. Some of it dulled a little on contact with the transparency. Oh well. Otherwise I’m very happy. The ridiculously small negative text even came out a little. Here’s the board before drilling and populating. It a simple MSP430 based alarm for when my two year old son opens the front door. He can now just reach the handle.

When I’ve got it all sorted (and have tried the via rivets too) I think I might do a proper write-up.