Tomu: A Microcontroller For Your USB Port

January 20, 2018 by Eric Evenchick 47 Comments

Looking for a ultra tiny development board? Tomu is an ARM Cortex M0+ device that fits inside your USB port. We’ve seen these in person, and they’re tiny.

There’s a few commercial devices in this form factor on the market. For example, the Yubikey Nano emulates a keyboard to provide codes for two-factor authentication. The Yubikey’s tiny hardware does this job well, but the closed-source device isn’t something you can modify.

Tomu is a new device for your USB port. It sports a Silicon Labs EFM32 microcontroller, two buttons, and two LEDs. This particular microcontroller is well suited to the task. It can talk USB without a crystal for timing, and has an internal regulator to generate the core voltage from a 5 V USB supply. Since it supports DFU firmware updates, it can be reprogrammed without any special tools.

Unfortunately, the EFM32 device lacks secure storage options, so the Tomu might not be the best device to keep your secrets on. That being said, it will be interesting to see what applications people come up with. The creators have suggested using the device for media buttons, sleeping and waking a computer, and as a U2F key.

The project is currently available on CrowdSupply, and all design files and source is available on their Github. If you like soldering tiny things, the twelve-part bill of materials should be fairly easy to assemble at home.

A breakdown of the various parts of the Game Tin

Game Tin: Handheld Games With No Batteries

October 16, 2014 by Eric Evenchick 54 Comments

Anyone who grew up with a Game Boy knows how well they sucked through AA batteries. [Nick]’s Game Tin console solves this problem by running of an ultracapacitor charged by solar power.

The console is based on a EFM32 microcontroller: an ARM device designed for low power applications. The 128×128 pixel monochrome memory display provides low-fi graphics while maintaining low power consumption.

There’s two solar cells and a BQ25570 energy harvesting IC to charge the ultracap. This chip takes care of maximum power point tracking to get the most out of the solar cells. If it’s dark out, the device can be charged in about 30 seconds by connecting USB power.

The 10 F Maxwell ultracapacitor can run a game on the device for 1.5 hours without sunlight, and the device runs indefinitely in the sun. Thanks to the memory display, applications that have lower refresh rates will have much lower power consumption.

The Game Tin is open source, and is being developed using KiCad. You can grab all the EDA files from Bitbucket. [Nick] is also gauging interest in the Game Tin, and hopes to release it as a kit.

OTM-02 Is A 3D Printed Wristwatch

April 23, 2013 by Mike Szczys 27 Comments

We love looking at roll-your-own wristwatch projects. Getting a project small enough to carry around on your wrist is a real challenge. But we think the OTM-02 wristwatch really hit the form factor right on the mark.

OTM stands for Open source Time Machine. It’s the work of [Hairy Kiwi] and he managed to bring the guts of the watch in at a thickness between 6.5 and 7mm. That includes the LCD, PCB, piezo diaphragm, and the battery. The PCB itself is a four-layer board built on 1mm thick substrate. It’s running an EFM32 (ARM) microcontroller which comes with hardware USB support. The little door sitting open on the side of the 3D printed enclosure provides access to the micro USB connector which can be used to charge the 150 mAh battery inside. That may not sound like much juice, but if you set the display to show minutes only [Hairy] calculates a battery life approaching 175 days. If you just have to have the seconds displayed you can expect about two weeks between charges.

Like the name says, this project is Open Source.

[Thanks Liam]

Roll Your Own LoJack Clone

February 13, 2013 by Mike Szczys 34 Comments

diy-lojack

If you’ve ever worried about your car getting stolen this hack can help give you some piece of mind. It’s a cellular enabled geolocation device. These things have been in use for some time, the most common brand we know of is the LoJack. That company gives you a little box to install on the vehicle and if it ever goes missing they can grab the coordinates and forward them to the authorities. This custom version builds a lot into an addon board for an EFM32 board.

The image above shows the main components of the add-on: the GPS module and the GSM modem. Along the top edge of the board is the voltage regulator circuits which aim to keep the standby power to the slightest of trickles so as not to drain the car’s battery. What you can’t see is the SIM card slot which is located on the underside.

You can find the Eagle files for the design at the link above. We’ve embedded the video description of the project after the break.

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Super Slim Wristwatch Build

December 12, 2012 by Mike Szczys 33 Comments

This slmwtch lives up to its name. When the LCD screen is folded back onto the PCB the entire thing comes in at just 2.35mm. That’s including a coin-cell battery not shown above. Wow!

Part of what makes this possible is the specialized PCB design. [Anders] didn’t want to add more thickness than the screen and battery so he make a cutout in the PCB design to accept each component. In this image it’s easiest to see on the two SMD resistor in the upper left. They’re held in a void by the two solder connections. Admittedly this is not going to be a mass-production friendly design. And we have concerts about the long-term stability of suspending components by their leads. But as a one-off it’s fantastic! See for yourself in the video after the break.

The control for the watch uses two touch sensitive pads on the back of the PCB. There is no backlight for the display which can be a problem when trying to read the time while outdoors. We wonder if an ePaper display with similar dimensions is available?

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