This Little QT Py Has Certainly Caught Our Eye!

There's been something of a trend of miniaturization in our development boards lately!

Inspired by perhaps the DigiSpark range of boards, there has been a running competition of who can pack what into the smallest footprint.

We've seen the likes of the OSHW-certified, five star-rated Serpente range of boards — pictured above — from arturo182, which have been sailing out of the shipping doors on Tindie, and even Seeed Studio jumped into the running of things, in releasing their Xiao board, seen below.

It's sometimes hard to come out with a completely unique product in these times where everything is so integrated already — there really are only so many ways you can place an MCU and support components onto a PCB — and when you are looking to boil that board down to the bare minimum, as these products do, not only in terms of board size, but cost also, well, as you can see, sometimes things will look a little similar...

Taking that train of thought just one step further, it's also likely that we at some point might see some reuse of the ideas behind naming, etc. That's granding for you though — a number of ideas that circulate around the form and function of the product.

Serpente relates to the fact that the boards love CircuitPython. Xiao has references to taking care of ones parents (fitting for an offspring board), or, can also refer to a Chinese end-blown flute, perhaps drawing more upon the physical layout of the board, with its castellated holes maybe resembling finger positions on such an instrument.

So when you've got a board that targets CIrcuitPython, and is just so adorably smol, well, QT Py makes a good deal of sense. Even if it doesn't have... much... to do with QT... I digress.

QT Py is upping the parts count on its smol board product entry, and the result is a really quite capable little box of tricks. Despite being size and pin compatible with the Xiao from Seeed Studio, this little QT Py has a few extra tricks up its sleeve that make it a bit more attractive for prototyping with.

The first one I can see, is instead of the shielding can found on the Xiao, QT Py has torn the lid off of things, and used the extra real estate on the top face of the board to shoehorn in a few extra bits of practical component placement.

We've got a manual reset button — which is really very handy when looking at any board that is using a bootloader — the need to physically disconnect and reconnect one end of the USB connection is no longer an issue!

Shuffled up next to that reset button is an additional I2C header, taking shape in the expected format from adafruit — the STEMMA QT connector series, providing the much needed context to the naming of the board — it's not about the display framework in this instance, and instead refers to the QT variant of the 4-pin header used for the I2C wiring.

While systems such as Grove, Gravity, and indeed, even the original STEMMA connectors all use an already small-ish pitch of 2.0mm, this isn't quite small enough for this new mindset of micro, minute boards.

STEMMA QT shrinks the pin pitch down to 1.0mm, using the JST SH range of parts. This change of pitch now means that they are using the same connector system, andpinout of the SparkFun Qwiic connector system.

This means you can daisy-chain boards to your heart's content — or at least until the hefty 600mA current output of the 3.3V regulator just can't take any more — that's still a lot of headroom!

In a world of proprietary connectors and adaptors, this is a welcome breath of fresh air!

This STEMMA QT connector also helps reclaim some of the many I/O pins of the ATSAMD21E18. With 26 I/O available on the chip itself, it's a real shame to see so many of them sacrificed in the pursuit of shrinking the size of the board.

Being pin compatible with the Xiao, and using the same processor, it seems a real shame that the 11 I/O mapped to the edge contacts of the QT Py, should leave 15 of the SAMD21 I/O unused.

Not content with leaving them to waste, the QT Py sees to it that as many of them are called into service elsewhere!

With a one of the SERCOM objects of the SAM D21 mapped to the STEMMA QT connector, that leaves 13 to go...

We find one mapped to an on-board WS2812, with indications being able to gate the supply voltage to the LED, so we can assume two I/O used there — one for LED data, one for power control.

11 unused I/O remain...

Flipping the board over, we see an unpopulated SOIC-8 footprint... Despite the never-ending party line that some internet commentators walk — that it all could have been done with a 555, no, that's not what we're looking at here.

With CircuitPython having bit of a memory footprint, any additional storage is always welcome. Unlock a huge amount of potential extra storage by soldering a bring-your-own SPI Flash chip onto this header, or I imagine that would be a great set of contacts from which to leverage yourself another H/W (SERCOM) SPI instance...

If you don't need the extra space — or even if you do — there's no reason you can't share that SPI bus with other devices... SCK, COPI, CPIO and a SS account for another four of the remaining I/O, leaving eight free pins. That's a darn sight more resource aware than the Xiao board design and allows for a very functional board in a tiny footprint!

QT Py is currently headed towards a pre-production batch, and I can't wait to see this dinky D21 development board up and running in a range of projects!

Sometimes you don't need every pin on a MCU to be utilized — and the QT Py has done a great job and breaking out as much as possible into such a small footprint.

UPDATE: The QT Py is now available, selling for just $6 while supplies last.