NFC Login 2.1


Version 2.1

This should be the final revision. Just a few minor tweaks. The regulator is now a TPS77533 rather than an incorrectly footprinted TPS77333. Corrected the bi-colour LED wiring. Move to a smaller 4MHz crystal for the USB side of things. Shrunk it a bit as I’m no longer expecting to find any PCB bugs. Dropped the 0.1″ pin header as the TagConnect worked fine.

The most obvious change is the small capacitive touch sensor PCB on the front. The previous version searches for a tag a couple of times a second. This works fine but I don’t like the idea of all the 13.56MHz EM noise pollution. This will poll for touch frequently and if it senses a touch it will poll for tags rapidly for a few seconds. In theory it could be more responsive too. Not had a chance to code this yet though.

There’s is also a Login NFC the way to another implantee. I’d recommend you check out Hans Peter’s blog.

Wicked Uncle – some great kids’ toys

home-boyI recently stumbled across a nice looking website if you’re stuck for a present to buy any kids that you know. I was mainly thinking about my own two boys, but to be honest it’s best set up to help out those of you without kids of your own. It really helps with questions like “What the hell is 6 year old girl into?” The site I’m talking about is

Anyway, I’d mentally noted that it might be a good site for something for my nieces and nephews – six of them ranging in age from 3 to 12. My two boys are 2 and 4 but I have a fairly good idea what they’d like. Anyway, they had a promo where 4 lucky bloggers could get a £40 voucher in return for an honest review. So for transparency, I got a voucher from them. That’s enough to persuade me to type a review. However £40 is definitely not enough to buy my integrity, so this is a genuine review.

The site

WickedUncleFirstly, the site itself. I’m a web developer myself so have no time for stuff that doesn’t work or is trying to be clever at the sake of usability. No worries here. It’s nicely laid out. You can narrow things down by gender, age and category (adventurer, role play, engineer, creative, etc.). With a bit of luck you’ll know at least there things about you godson / neice / friend’s spawn. I like it. Really useful. Age suitability for toys always seems a bit difficult as kids are so different, but it seemed to work.

I noticed is that the site was fine to use on a mobile device. No glitches or tricky bits. I did think at one point that it would be handy to allow different presents for different kids to be delivered to different addresses. Then I thought how no other sites do this and it was probably a bit of a big expectation. Lo and behold – I found in the FAQ that they used to do this and decided to discontinue it. Not too surprising I suppose.

Gift wrapping in an option (£2.95 for the first one, then £1.50). As is a card (£1.95). Both seemed like great options if you want to send it direct. However, as I wanted to check out the toys myself I didn’t chose either of these. Sound OK though. And just a simple message can be included free.

The only grumble I had about the site was that it insisted on a password to create an account. For a site that you might only ever use once, I thought this was a bit too presumptuous. I may well use it again, but if I do then I’d be more than happy to enter my details again.

The toys

I did notice quite a few toys on there that we already had. A good sign – they’re all toys that my kids like. It seemed very much like a small range of quality stuff rather than a store stuffed full of everything. Ideal if you’re trying to narrow stuff down a bit. Anyway, here’s what I picked:

T4 Transforming Solar Robot

wp-1450299890843.jpgI picked this thinking it might be suitable for my nephews who are 5 and 7. They love Lego and are pretty capable with this sort of thing. The specified age range (8) seems realistic though. I was too optimistic and Wicked Uncle were right. Inside it’s much more like an old Airfix kit. Lots of parts on sprues. (I bet you didn’t know that’s what those unused bits were called.) It looks good but it will have to head to an older nephew instead. It also meant I couldn’t try it out and review it properly before I sent it. Looks good though.

Magnetic Stacking Rocket

wp-1450300101982.jpgI got this because one of my boys (2 a couple of days ago) loves the plane version of this. It’s a nice toy. There aren’t too many pieces and the magnets hold them together nicely. Clumsy little fingers from 1 upwards can still put it together easily without lining thing up too accurately. He’ll be getting this for Christmas and I know he’ll like it. A bonus for those of us with a puerile sense of humour – one of the pieces looks like a boob. Check the photo and see if you can guess which one!

Hexbug Scarab
Not so impressed with this one. It says age 8, but I’d say maybe lower. I thought the Hexbugs did intelligent stuff like line following or turning round when then bump into things, but this just scuttles along. It goes quite fast and does seem very insect-like. My 2 and 4 year olds will love it, I’m sure, but that’s all it does for £12.99. For some reason I thought it was a crab and expected it to go sideways, but I can see it’s my mistake.

Zombie Aquabot Fish

635733509581622000Fairly simple, but very nice. My son previously had a similar fish but the tail broke off before he could even use it. This one seems sturdier and swims nicely. It seems to vary speed randomly. No idea if it’s supposed to but that works well and makes it seem more realistic. It just floats up to the surface slowly so that makes it quite realistic rather than just a floating toy. The fact that it’s a skeletal shark will go down well. The glow in the dark bit? I can’t say I actually tested that. I’ll let the boys try that bit out.

Well, there we have it. I can genuinely recommend the site. Ideal if you’re not quite sure what to get. (A nice change from a list of demands!) Absolutely perfect if you’re outside the UK and the child you’re buying it for is here.

NFC login 2.0 finally working


It’s taken some time, but it’s finally working! It’s hard to debug when you don’t know what’s at fault.

  • Is it the PCB design? I’ve never done anything as complicated or as high frequency as this.
  • Is the the PCB manufacture? I decided to get the board made by DirtyPCBs rather than home etching, so at least that took one potential source of screw-up out of the equation.
  • Is it my soldering? I’ve never done anything as fine as the LQFP (larger chip) and QFN (smaller one on the right). They’re both 0.5mm pitch but at least the LQFP has pins that stick out rather than just metal patches on the edges of a square block.
  • Is it the design of the antenna? This is the work of the very talented Mathieu Stephan (from here) so probably not the weakest link.
  • Is it the firmware? I’ve had the code running on a MSP430F5529 LaunchPad, but I’ve switched down to a smaller F5510 and reassigned the pins.

Well, it took three tries – as you can see from the scribble on the board above. There’s a mistake around the TPS77333 voltage regulator which truned out to be a footprint error in the Eagle-supplied libraries. It’s now a bodged-in TPS77533. There’s another by the LED which I’ve had to swap for two separate ones rather than a red/green single package. My mistake on the pinout there.

It turns out the problem was the soldering of the QFN packaged TRF7970A. Buying a microscope helped me sort it out and it’s finally there! It’s finally working! There’s more to do, of course. I need to fix the mistakes. The software could be tidier. Version 2.1 will be perfect (probably). I’ll publish the design and code when it’s tidy, but in the mean time if anyone’s interested in any of it, let me know.


I laser cut a simple acrylic enclosure. It’s just black acrylic on the back – with some 5mm neodymium magnets press fitted into holes so it attaches firmly to my PC.
Some clear acrylic makes up the front so I can see the LEDs and the fruits of my labours. M3 nylon bolts go into threaded holes on the rear piece.

It’s been harder and slower than I expected but I’m very happy.

A stereo microscope

Wow. I didn’t really think I needed a “real” microscope. So far for working on those tiny SMD components I’ve got by with a jeweller’s loupe and a magnifying headband from my father-in-law who is a retired dentist. For inspection afterwards, I used a £20 eBay USB microscope. This all seemed adequate.

However, for the latest version of my NFC login project I had to solder a TRF7970A NFC transceiver. These only come in QFN package. The 0.4mm pitch pins aren’t too much of an issue. I can handle these OK on the LQFP package that the MSP430 comes in. It’s the fact that there aren’t actually any pins sticking out – just a visible metal pad on the lower edge of the chip. I had to rework one a few times as I hadn’t got it quite right and I suspect I was starting to do some damage to the chip and/or the PCB.

I did a bit of research – mostly on eevblog. The really good ones are way to expensive for the amount of use it. The good value AmScope models that most people recommend are too expensive to ship outside the US. Brunel microscopes in the UK seem good, but still quite pricey. Then I stumbled across the usual eBay “bargain” direct from China. I’ve been happy with the price/quality compromise on the laser and CNC mill I got this way. Time to dig a bit deeper and see of this is likely to be a good idea.

Microscope1I found a very helpful review on eereview that served to be the same model. To be honest, it seems the same as some of the AmScopes too. It actually looks the same as the BMDZ series from Brunel too. I decided to risk trading off quality for specifications and went for it.

Here’s the image straight from the eBay listing. I assume the seller won’t mind as I’d be happy to recommend lapsun_gift. The microscope (plus some x0.5 and x2 barlow lenses) arrived in about a week. It was marked a $95 but form some reason UK customs decided to charge me VAT on £125. The cost was about £300 so I was OK with that. The same microscope without camera, ring light or barlow lenses was £450+VAT in the UK so I was happy with the price too.

wpid-wp-1448207092901.jpgI’m very happy with it. Inspecting a reworking LQFP used to be a pain. My USB microscope would allow me to see stuff but the lighting meant I couldn’t really be sure what was a short of solder and what was a reflection. The actual soldering had to be done with no magnification and then re-inspected. Now I can actually see properly. The microscope itself is 7x to 45x zoom. With the 0.5x lens I get less magnification and a 165mm focal length and can actually solder under it – whether an iron or hot air. Zooming in (and perhaps removing the barlow lens) means I can actually see the individual balls in the solder paste.

The 2x lens (i.e. up to 90x magnification) is a bit much for anything other than really detail inspection of a PCB. It should be great for counting a spider’s eye with my boys though – if it’s not too scary!

WIN_20151122_16_23_58_ProThe camera is probably the weakest point of it all. When switching the camera in, you lose one of the stereo eyepieces. Not really a problem. However, I find the the image the camera sees is about 10% of what you see through the eyepieces. Focusing is tricky and I can’t see to get it to focus at the same place as the remaining eyepiece. In the image shown each pin is about 0.2mm with 0.2mm gap to the next one. Through the eyepiece you can see the whole 48 pin chip and some passives around it. It’s also far clearer. That photo really doesn’t do the microscope justice. Never mind – the camera was just a “why not” addition. I might try an adapter for my SLR camera at some point but no hurry.

Many people recommended a boom stand. This didn’t come as an option with the eBay model, but if I ever need one I can always add one later. The supplied one is certainly adequate for me so far. If I need to look at an angle I just tilt the board and refocuscam.


NFC Login 2.0 – the first custom PCB I ever ordered

Home etched v2.0 - dodgy solder mask and via drilling

Home etched v2.0 – dodgy solder mask and via drilling

NFC Login version 1.0 is working fine, but I always intended to ditch the development boards and create a custom PCB with just what’s needed. As always it’s finding the time to do these things. I had an attempt at a home etched one, but it didn’t go quite right. Then I was busy with the new workshop so it got put on hold. Eventually I decided that the 2 week wait for a PCB from China was actually quicker than finding time for the few hours it (in theory) took me to etch a board.

NFC Login 2.0 PCBs

NFC Login 2.0 PCBs

As it seemed very likely that there would need to be a further iteration, I decided that the cheapest option of using DirtyPCBs would be fine. I must say I’m fairly impressed with the quality. The only minor issue I had was that they seemed to use the tNames rather than the tSilk layer for the silkscreen. As likely to be my fault as their, I’m sure. Anyway, this was the result. Not bad for $25 including shipping for 10. That’ll give me scope for ruining a few too!

I started just adding a few components – just the minimal the USB and MSP430 parts – expecting that I’d find a problem. All good. Even the tiny TagConnect header worked fine. The only snag I can across was an incorrectly sized footprint for the TPS77333 regulator. This was annoying as it came from the TI library included in the latest version of Eagle. An earlier version the library which I used for the laser coolant monitor was fine. Annoying. Somehow it also seemed to struggle with the supply voltage when flashing an LED, which made debugging flaky, so I bodged a 77533 (higher power, different pinout) sideways across the board. It works. It’ll be updated in the next revision.

Populated board - note the bodged regulater on the right

Populated board – note the bodged regulator on the right

All seemed OK, so I added the NFC side of things. Things here were more problematic. Currently it seems that communication (SPI) between the microcontroller and the TRF7970A are OK. What I can’t seem to get in any output at all from the NFC chip into the RF circuitry. The 13.56MHz crystal seems to be working fine. This could take me a while. I had a few goes at removing and reattaching the TRF7970. Lots of practice reworking those tiny 0.4mm pitch QFN and LQFP packages, but there’s a chance I’ve damaged it. Maybe I need to populate another one to check.

CNC mill upsize

I’m very fond of my Proxxon MF70. I converted it myself and its what got me into the whole world of CNC. It’s great but the size does limit what it can do.
Since getting a new workshop I’ve been thinking of what to fill it with. Actually, that’s not quite true. I had an idea of some things to fill it with before it was even built. I just couldn’t buy them.

Sieg X3

I didn’t go for a Sieg X3

I’d been keeping an eye out for a bigger CNC mill for a while. Whilst I did consider a “proper” mill like a Sieg X3, these are really heavy, expensive and needed a lot spent on CNC conversion. To be honest, whilst it’s nice to be able to easily mill large chunks of metal I knew I wouldn’t be doing it all that often.

I’d learnt from tinkering with my CO2 laser cutter that cheap Chinese machinery is good value if you’re prepared to improve their shortcomings. The popular eBay CNC3040 or CNC6040 machines definitely fall into this category. It’s more of a router than a mill, but is apparently capable of machining aluminium if you’re careful.

I’d been watching for a while and some went for silly prices near the £1000 or so new price, so I was happy to snap one up for £615 including a few upgraded controller components. It had a slightly damaged table no doubt from some missed Z steps. slowly ramping the  endmill into it. It had the older blue (total junk) controller box which I was going to replace with a Gecko 540 I had hanging around for just this sort of thing. It has the older Huanyang VFD to drive the water cooled spindle but it seems this is easier to control using Mach3 than the newer Nowforever ones.

The new mill dwarfs the old one

The new mill dwarfs the old one

It arrived and I unpacked it. It’s so much bigger than my old mill. The spindle alone is about as big as the old table!

I was a little disappointed to find that the table was a bit worse than it looked in the photos, but I carefully filed it down so it was at least flat and turned the T-slot pieces around so the damage wasn’t in the centre. The bigger shock was the badly stripped threads on the main gantry assembly and the horribly bodged limit switch wiring. Oh well – nothing a little time and care wouldn’t sort out.

I fired it up using the blue box. One axis tended to freeze in one direction. It seemed to be the controller board rather than the stepper drivers. Switching to another of the 5 channels helped but it still missed steps occasionally. Moving from 16 to 8 microsteps helped again, but then it started really misbehaving. Time to ditch it and go Gecko. I’m not going to waste any more time putting lipstick on the pig that is the electronics. I’ll replace all the wiring with shielded stuff too.

A new workshop (part 2)

So the company who built and installed my garden building have done their bit. Now it’s time for me to turn a lovely garden office into a proper workshop / man cave. The included options of wood flooring or carpet tiles didn’t really suit me. I decided on a single piece of grey vinyl flooring from Factory Flooring Direct. I wanted something fairly hard wearing that could stand up to the abuse of a workshop and cope with any spills. The ply that the installers put down was a rather pointless 6mm, so that was ripped up and a sturdy 18mm ply base put down. My brother gave me a hand cutting the vinyl to fit as it wasn’t an easy job – especially with my attention for detail and the fact that I didn’t want skirting board to hide any gaps. It was hard for a number of reasons. Firstly, the roll was too heavy for one person to lift. Secondly, as it was one piece it was bigger than the room and hence hard to manhandle. We did it though. I now had a nice tough grey vinyl floor.


Workbenches fitted

Next was the workbench and shelving underneath. Being spoiled for space somehow made it harder to work out what I wanted and how I would lay it out. I settled on using some solid beech Hammarp kitchen worktop from Ikea. I intended to use oak but when I actually saw it the beech looked better and was cheaper too. The walls only really have decent support at the joins between the prefabricated panels so I used some steel angle iron along the walls and 30mm stainless steel legs to support it. All the metal is from Metals4U. The desk drawers are Ikea Alex and the kitchen units Ikea Metod / Maximera. Basically – it’s mostly an Ikea kitchen! That gives me some desk height (73cm) and mostly workbench height (93cm) space. All of this was meticulously fitted to the not-quite-straight walls so there was no gap. I borrowed a kitchen worktop jig to mitre and biscuit joint the worktop. Lots of work but worth it to get a good fit in the end. The under-bench shelves are just melamine panels – some 30cm and some 45cm deep. You may notice there are lots of sockets. You can never have enough sockets. There are 11 double sockets – some above and some below the worktop. There will also be one on the outside for garden power (hedge trimmer, etc.). The ones by the desk are always powered, but I carried over an idea from my previous workshop. The ones at the workbench can be isolated using an emergency stop button. It’s not just used as an emergency stop. I mainly to make sure that if the kids wander inside all the dangerous stuff and power tools can’t be switched on. I trigger it as I leave.

Moving toys in

Moving toys in

This is how the workshop looks after I’ve moved some of the equipment in. From the left you’ll see:

  • My desk for coding and microcontroller work (where I’m typing this right now)
  • Oscilloscope and solder station
  • An Up Plus 3D printer
  • The red emergency stop button on the wall
  • My small Proxxon MF70 CNC mill
  • A 40W CO2 laser cutter
  • A small metalworking lathe
  • A mitre saw
  • The kid’s workbench. They want to be like their dad!
  • The keen-eyed will have spotted 2 fire extinguishers (powder and CO2). I’ll be burning things with a laser in a primarily wooden building so a sensible precaution.
You'd never know it was a workshop from outside

You’d never know it was a workshop from outside

All this stuff only really takes up half of the workshop – the mostly hidden half. The right hand side should soon be getting a sofa bed (for the occasional brave visitor), fridge, etc. It’ll be a family space and my wife will have her input. However, I have said that if a scatter cushion appears it’ll have an accident with the mitre saw.

There’s still workshop stuff to do. There’s plenty of storage space under the bench but shelves and wall-mounted tool boards are coming soon. The laser isn’t usable yet as it has no exhaust venting. I’m also planning to put a sink in there to allow making a cup of tea and washing hands. It’ll drain onto the ground rather than have any plumbing back into the drains so it’ll be fairly limited. I’ll let the rest evolve as needed. Maybe it’ll never happen but the plumbing is there.