Signet High-capacity

by Nth Dimension

An all-in-one encrypted USB flash drive, two-factor authentication token, and password manager

View all updates May 20, 2019

Development Board

We received development boards for Signet HC recently. These boards are larger than the final PCBs to allow more signal lines to be exposed for debugging and so that we can get the boards more quickly. If we used the tight tolerances the final production boards will need the turnaround time would be weeks longer and much more expensive. Other than having fewer pin headers the production PCB will have a similar set of components as this PCB. The main difference will be that parts will be used that have the same functionality but smaller footprints and the routing will be better optimized for space. You can see both sides of the development board below:

Initial testing

One of the first things we did was look at the quality of the critical Signals for the board. We ran the microcontroller at 216 Mhz and the SD interface at 48 Mhz, the maximum speeds supported. We found no significant noise on any of the critical signals such as the microcontroller’s oscillator, the voltage regulator’s power "good signal", and the SD card clock line. We also performed a number of functional tests. Like many developers would we first tried a blink test which you can see below:

There is more going on in the test above than is apparent. The blinking stops when the button is pressed which validates the button circuit. Also before the blinking starts the test attempts to read and write data to the SD card. If the SD card test fails the LED’s would transition to an always-on state instead of switching off.

USB High-speed

One of the things we worried about most was whether the high-speed USB interface would work. It took a little time debugging the startup code but without any hardware changes we were able to get the USB high-speed interface to startup and the device was recognized as a high-speed USB device by one of our desktop computers. This was a limited test and we will follow up soon with bandwidth and error rate testing.

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Product Choices


Signet HC

An all-in-one physically secured USB flash drive, authentication tool, and personal information manager you can take with you wherever you go.


USB Extension Cable

Helps keep your Signet HC close to your keyboard when the closest USB port is too far away. Can also reduce strain on the device's connector to increase its lifespan. 3'

USB Extension Cable


Micro-USB Host Adapter Cable

Connects your Signet HC to a USB-micro Android device. 6"


Nth Dimension

Producer of privacy and security focused open source electronics.

Neils Nesse


Mingjane Wu

Technical writer / UX designer


PCBA Manufacturer

Sea Sky Tooling

injection molding

See Also

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