chester's blog

technology, travel, comics, books, math, web, software and random thoughts

Got an NFC/RFID chip implanted in my hand

26 Feb 2022 | Comments

RFID + NFC = NExT implant

NFC (the tech used in mobile phones for contactless payments and contact exchanges) and RFID (used in product identification/tracking, building access cards and many other things) are found everywhere these days. I played a little bit with cheap tags that can be used to interact with phones, but implants are getting more practical, so I decided to give one of them a go!

(I know, I know: technically, NFC is a set of protocols built upon a subset of the RFID ones, but I’m going with the commonplace usage of the terms: “RFID” for the unregulated “low frequency” 120-150 kHz tags that use all sorts of proprietary protocols, “NFC” for the “high frequency” 13.56 Mhz devices using specifically NFC)

I didn’t want to limit myself to a single technology (or to go with two implants), but Dangerous Things (yes, that’s the company name 😅) sells the NExT: an implant with both an RFID chip (that can simulate - or “clone” - fobs and tags on the wild) and an NFC chip (which can store 888 bytes of data, accessible to any NFC reader I touch, including smartphones).

The contraption used to inject it (after the fact) and some specs

There are some limitations: its NFC can’t be used for payments (like, for example, the Walletmor), and the RFID can’t emulate super advanced security, or hold multiple tags, but the combination is enough for a lot of uses, plus it’s a field-tested set of chips that should be operational for years and years, so I chose it.

Atari 2600 on a breadboard, part VI: fixing the video, adding a joystick and wrapping up

26 Sep 2021 | Comments

It has been a wild ride, and it finally comes to an end. Here are the final tweaks I’ve added to this project, which results in a mostly working Atari 2600. Most importantly, I learned a ton and had a lot of fun. If you came so far, I hope you did too!

Atari 2600 on a breadboard, part V: RIOT and Audio (and running actual games!)

12 Jul 2021 | Comments

After Hello World

Now that I got Hello, World! running, I feel confident this project may actually succeed! 😅 The next step is to run an actual game, which requires wiring the last chip (and, due to the poor video I have so far, a sound circuit).

Atari 2600 on a breadboard, part IV: clock + composite video = Hello, World!

04 Jul 2021 | Comments

TV Time

In the previous post, I had the CPU, cartridge and TIA wired and tested, but still needed the Arduino to make them tick and check the resuts. All those hex numbers were fun to debug, but let’s get to the real deal: plugging it to the TV.

Atari 2600 on a breadboard, part III: tidying up and adding the TIA (video chip)

25 Jun 2021 | Comments

Tidying Up

In the previous posts I made the CPU work on the breadboard, then added a cartridge connector, all using jump wires - which can be easily reconnected, labeled, etc., but have a downside: they disconnect easily. Coupled with the equally flimsy cart connector, all my attempts at moving on with the project would result in failures.

After seeing Ben Eater’s beautiful breadboard computers I decided to rewire the boards I already had. For that, I’d have to rethink my cartridge connector: instead of having the jumper cables going out of it (left), I got some long pin female headers that extended the pins so the connector now fits the board like any other chip (right):

cart, before and after

Atari 2600 on a breadboard, part II: reading a cart

14 Feb 2021 | Comments


A long time ago I grabbed the three chips from a broken Atari 2600 (Jr.), to see if I could build an Atari with them on a solder-less “breadboard”. My first attempt (post here) was to drive the CPU with an Arduino, which showed the chip advancing through what it believes to be memory, but is actually just a single “no operation” (NOP) hard-wired instruction:

cleaner version of the 6507 memory walk on a breadboard

It took some time (between finding the right connector, 3D-printing a part, figuring out the wiring and fixing the Arduino software), but I finally moved on to the next step: plugging a real Atari cart and seeing some actual code running!

Building a classic XBox to USB adapter (to use a RedOctane Ignition DDR mat to a computer)

19 Jul 2020 | Comments

As a Dance Dance Revolution (DDR) enthusiast on its heyday, I spent a lot of time adapting dance pads to improve comfort and durability, until I got myself an Ignition pad. Its thick rubber interior, superior sensors and RedOctane (of Guitar Hero fame) quality resulted in no mis-/over-/continued registering of arrows, less knee strain and happier downstairs neighbours.

My Ignition pad from the 2000s

I sold that one years ago, but having some floor space and time now, I decided to buy a “new” one on eBay. Not having a Playstation these days, I planned to use Stepmania (the open-source DDR clone), but my mat was missing the USB adaptor. A Playstation-to-USB one gets recognized, but arrows do not register correctly.

The adaptor I needed would plug in the XBox connector (classic XBox controllers are quite close to USB in nature, as we’ll see below). They are near-impossible to find, but it seems the breakaway cable that came with the controller can be converted into such an adaptor.

Detecting TV power state via USB

03 Jun 2020 | Comments

One convenient feature of Chromecast is that it turns on your TV automatically when you connect to it - as long as your TV has HDMI-CEC. Mine doesn’t, but it is already remote-controlled via Raspberry Pi, and thanks to Home Assistant, I can easily detect when the Chromecast is in use, so in theory I could just blast a command to the IR when it switches away from “off”.

There is just one problem: Home Assistant doesn’t know whether the TV is on or off. If it is already on when I start casting, sending the command will turn it off - the opposite of what I want. Also, I would like to turn the TV off when not using the Chromecast (something it doesn’t seem to do, even with HDMI-CEC).

ZX Spectrum Next

25 Apr 2020 | Comments

The ZX Spectrum Next was a Kickstarter-backed initiative aiming to recreate the iconic ZX Spectrum using FPGA and lots of ingenuity. I am a bit too Marie-Kondo-ed for physical retrocomputing these days, and, on top of that, have been skeptical of such projects (for good reasons).

However, this one had names like Victor Trucco (one of the most respected Brazilian retrocomputing hackers) and Rick Dickinson (industrial designer behind several Sinclair computer cases, who sadly passed away before it was finished) behind it, so in May 2017 I gave it a shot and backed the campaign in exchange for a unit.

Expected to ship January 2018, it was delayed for more than two years, but for good reasons: the people behind the project would not accept anything but the best quality, continuously pressuring manufacturers to go on-spec. And it was worht the wait - the computer is sturdy and gorgeous:

click to enlarge

Enable dynamic DNS (DynDNS, Duck DNS, etc.) inside networks without NAT loopback support on router

18 Aug 2019 | Comments

Dynamic DNS providers like DynDNS or Duck DNS are great to let you access software like Home Assistant running on your properly secured computer or Raspberry Pi from anywhere.

One problem that I was having with them: the custom URL did not work inside my network, just outside. That happens because my router does not support NAT loopback, blocking any requests from the internal network to the external IP (which is what my custom domain points to).