A HVTPI adapter plugged into a USBASP, with a an IDC10 cable plugged into it in turn

HVTPI Primer And Toolkit Equips You For BOM Substitutions

Novel programming interfaces for MCUs might catch us by surprise, but then we inevitably get up to speed with the changes required. Today’s bastion is HVTPI – a “12V reset” addition to the TPI we’ve just started getting used to, and [Sam Ettinger] has shared a simple circuit to teach us all about it, along with PCB files and detailed explanations of how it all works.

HVTPI is an add-on on top of TPI, for which, as Sam explains, you need to hold RST at 12V when TPI would have it be low logic level, and leave it at Vtarget otherwise. For that, he has designed a variety of interposer boards of various complexity and requirements; explaining the choices behind each one and clearing up any misunderstandings that might occur on your way. All of the board files (and the TPI write-up copy) are caringly shared with us in a git repository, too! As a result, if you have an USB-ASP or an Arduino available, now you also have everything to do HVTPI, thanks to Sam’s work and explanations.

We’ve been covering Sam’s exploits before, and can’t help but be grateful for the stop-and-explain detour along the way. HVTPI being used on very small ATTiny parts, we wonder if something new in the vein of his recent FPC board able to fit and function entirely within a Type-C cable end!

With chip shortages, investigating programming interfaces for small and obscure yet in-stock microcontrollers has been, quite literally, paying off, and if you got some projects that need a MCU but won’t consume a whole lot of resources, it could be time to give an ATTiny10 a go. What’s the worst that can happen – you make the smallest chiptunes ever?

USB Arduino Into AVR TPI Programmer

Turning an Arduino of virtually any sort into a simple AVR 6-pin ISP programmer is old hat. But when Atmel came out with a series of really tiny AVR chips, the ATtiny10 and friends with only six pins total, they needed a new programming standard. Enter TPI (tiny programming interface), and exit all of your previously useful DIY AVR programmers.

[Kimio Kosaka] wrote a dual-purpose TPI and ISP firmware for the ATmegaxxUn chips that are used as a USB-serial bridge on the Unos, and constitute the only chip on board a Leonardo or Micro. The catch? You’re going to have to do a little bit of fine-pitch soldering. Specifically, [Kosaka-san] wants you to get access to an otherwise obscured signal by drilling out a via. We’d do it just for that alone.

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Breaking Out The ATtiny10

Atmel’s ATtiny10 is the one microcontroller in their portfolio that earns its name. It doesn’t have a lot of Flash – only 1 kilobyte. It doesn’t have a lot of RAM – only thirty two bytes. It is, however, very, very small. Atmel stuffed this tiny microcontroller into an SOT-23 package, more commonly used for surface mount transistors. It’s small, and unless your ideal application is losing this chip in your carpet, you’re going to need a breakout board. [Dan] has just the solution. He could have made this breakout board smaller, but OSHpark has a minimum size limit. Yes, this chip is very, very small.

Because this chip is so small, it doesn’t use the normal in-system programming port of its larger brethren. The ATtiny10 uses the Tiny Programming Interface, or TPI, which only requires power, ground, data, clock, and a reset pin. Connecting these pins to the proper┬áprogramming header is easy enough, and with a careful layout, [Dan] fit everything into a breakout board that’s a hair smaller than a normal 8-pin DIP.

The board works perfectly, but simply soldering the ATtiny10 to a breakout board and using it as is probably isn’t the best idea. The reason you use such a small microcontroller is to put a microcontroller into something really, really small like ridiculous LED cufflinks. A breakout board is much too large for a project like this, but SOT23 test adapters exist, and they’re only $25 or so.

Either way, [Dan] now has a very, very small microcontroller board that can fit just about anywhere. There’s a lot you can do with one kilobyte of Flash, and with an easy way to program these chips, we can’t wait to see what [Dan] comes up with.