SQFMI Is Frankly on a Roll with Their Latest Gadget — Franky!

SQFMI is a design firm with technically proficient, yet simple, minimalist design ethic.

We've we've kept an eye on them previously, closely watching the success of their iterations of Watchy — an ESP32-based smartwatch — which itself has gained quite a following of people keen to sport this trendy timepiece.

Perhaps as a culmination of a number of events of the last parts of this year — notably the release of the Nintendo Game and Watch console, and a fire sale on Twitter of some incredibly slick looking Sharp memory LCD panels — the latest release from SQFMI Labs looking like it may have been the brainchild inspired by both of these events, and Franky looks frankly ridiculously good fun,.

There's a distinct market for retro emulators — we've seen makers pull them together from protoboard, or even push to production with such devices as the PlayDate.

The joy of modern microcontrollers, and the power they pack means that running a retro emulator, such as one capable of loading the classic SNES games is well within the reach of anyone who can solder down an ESP32 module.

If you've managed to solder up one of the various "challenge" coins — and have it function — there's a good chance you can rise to the challenge of building a platform like Franky here.

Let's be Frank about this...

First and foremost, the front face of Franky doesn't give us much to write home about, but let's give it a quick look over and see what there is for us to figure out.

The most striking front facing feature of Franky is the 400 x 240 pixel Memory LCD panel.

Memory LCD is a slightly niche display technology, sitting somewhere halfway between a LCD panel and a ePaper display, both in terms of functionality and power consumption.

Although still a transflective display technology — e.g. it isn't (normally) backlit, and functions by physically flipping pixels between a reflective and non-reflective state, it still needs a touch of power trickling in to keep the image displayed.

However, while it isn't the effective zero power consumption of an EPD display, it is still remarkably low power, making it pretty attractive proposition for portable, battery powered gadgets, especially given the pretty speedy refresh rates we can see with the GIF above!

The buttons are provided as a set of interdigitated finger electrodes, a set of eight, arranged as two, four-way D-pads. With plans to supply a conductive set of button overlays, that should be just what's needed for a nice tactile response for your button bashing.

But for the more techie, tactile touch sensation, we can see some pads that indicate a fallback of some SMD tactile switches, should the end user prefer the minimalist appearance!

Don't judge a board by it's cover...

As with most things — a story, a viewpoint, an opinion — a PCB is no different in that there are usually two sides to it. And in contrast to the fairly simplistic front face of Franky, the rear of the PCBA shows us where all the fun bits are hiding away!

With nearly all of our eyes likely initially drawn to the rather smartly modelled ESP32-WROVER SoM, we are left with little doubt as to what's running the show on this board.

But with a bit of a closer eye, it's clear that Franky has aspirations that fly higher than a simple SNES emulator.

With no names visible in the render for us to work with, we'll take a high-level look at the loadout of parts we can see populated in place on the rear face of Franky.

There's a fair bit going on, so let's break it down a bit.

First up, we've got a RTC — real-time clock, that we can only (pretty fairly) assume is the DS3231M — an eight-pin SOIC packaged RTC that includes a factory trimmed MEMS oscillator, explaining the lack of visible crystal in the image.

Moving towards matching the accelerometer...

A "triaxial accelerometer with gesture recognition" is quite a feat, when the part we're looking at is so tiny!

By scaling *roughly* against the 1.27mm pitch of the DS3231M next to it, we see it is just slightly larger than the pin pitch of the SOIC-8, I'd call it at some 2 x 2mm, which makes the Bosch BMA4xx series a likely candidate.

The BMA423 looks a likely candidate, with its tiny footprint and noted gesture recognition capabilities

Expand your hor-I/O-zons...

There's a pretty high-pin count SSOP-28 sitting below the RTC. Given that we are fairly certain the RTC is an I2C device, as we are of the accelerometer, poking about for I2C interfaced port expanders with plenty of pins, points towards something like the PCA9555.

This part fits well with the surrounding components, namely the two resistors sitting on pins 2, 3 and 21 of the package, which match the address strapping pins of the device, along with a decoupling cap up at pin 24 where we'd expect to see one on VCC.

If we follow the tracking, it almost appears that this part is handling the button elements, so perhaps there is indeed a need to get something in the way of a conductive button overlay put into use here. We'll have to wait to see more details on the implementation of that.

Shifting things up a bit...

Finally, sitting below the port expander, we see a small 6-pin SOT device, with "5V" labelled next to it. With nothing but capacitors visible around it, this is either a switched capacitor DC/DC boost converter, or SQFMI have gotten a bit sneaky with which models they have pulled into this render.

Despite the fact that accelerometer (whichever it is) is likely good to 1.8V, and the WROVER good with 3.3V, the display panel itself gets a bit flakey below anything less than about 3.6V.

Boosting the system Vcc to 5V for the display means it will operate reliably, and the extremely low operating current of the panel means that a switched capacitor converter is a cheap, viable way of generating the meager amount of current needed.

The sound from all around

With the ESP32-WROVER forming the basis of many of the audio-targeted Espressif audio application demo boards, the module is more that capable of handling some decent quality audio data.

There's an I2S interfaced MEMS microphone visible — at a guess, perhaps something like the Invensense ICS-43434. With the component locations around the device matching — including the pulldown resistor specified for the SD line, and for the fact it's one of the few I2S mics that interfaces well with the I2S module on the ESP, it seems a likely candidate.

With a "bottom ported" package, the device is listening to audio through a via in the PCB, enabling it to hear things from the front of the device, despite being mounted on the rear.

Turn it up to 11!

With even more audio goodies such as a stereo I2S DAC with what looks like a built in pre-amp, there's a pretty limitless headroom to the amount of chip-tune sounds that Franky should be able to faithfully reproduce.

I'm not too far into the digital audio world, but the layout of this DAC looks close enough for me to be a match to the UDA1334 — and if we take a peek at the layout from the Adafruit breakout board for this part, we can see that the tracking is near enough spot on.

Loading...

It all starts with the USB-C connector. Again, it's worth pointing out that USB-C != USB3.0, USB-C happily passes USB2.0 signals, allowing the new connector standard to make its way into our lower speed projects.

Unmarked yet again, at the bottom of the PCB render, we see a small QFN package responsible for handling the USB-Serial interface to the ESP32 — remember, this WROVER is the previous generation ESP32, not the new S2 variant that contains the built in USB interface!

I'd bet a beer that this is a CP2104N, as not only is this a part quite commonly seen with ESP32 designs, but also with a similar enough pinout. I am all but convinced convinced this is the converter that has been chosen here.

We've got a Li-Po charger that could be any of a large number, so I'll not hazard a guess at that.

Heads Up!

The final feature of Franky that I'll focus upon is the 40-pin DIL header, that aims to replicate some of the connectivity and interfaces present on the boards that are normally associated with this connector, usually found on far heftier single board computers.

It's a neat idea, as many of the serial bus interfaces of the ESP32 can be mapped to the corresponding pins, where possible, of the 40-pin "Raspberry Pi" header, allowing for endless expansion, given the number of hats available for the Pi ecosystem.

Itty-bitty 8-bit doo-hickey

All in all, the combination of the fast-response transflective memory LCD panel, in conjunction with the powerhouse of the ESP32 running the show, this looks like a pretty pokey platform for playing with either your favorite 8-bit classics, or the plethora of Pi Hats and Bonnets that you might have about the place.

SQFMI were kind enough to share a few snapshots of Franky as it exists as I've been wrapping up this article, and with the image above in hand, and some well reasoned answers to a few questions posed to the design team, they've confirmed the components we've identified.

So while the sources aren't there just yet — they're coming, and with a design as polished as this, we can smell crowdfunding around the corner...

I'd suggest keeping an eye on their little teasers over on Twitter, (@SQFMI) — I know I'm keeping a close eye on Franky, so here's hoping they can wrap up on Watchy in due time, and get their focus on Franky!