The Hackaday writers as well as visitors are currently working hand-in-hand on an offline password keeper, the mooltipass (click to see the job description).
Next in our established on Hackaday series, we present the very first version of our schematics. There’s already been a great deal of discussions going on in our devoted Google group, primarily about the project’s fundamental functionality. since our firmware designers wished to get to work, we chose to send the very first version of our hardware into production a few days ago. before going with the schematics, let’s evaluation the needed listing of the mooltipass’s core components:
an easily-readable screen
a read-protected smart-card
large flash memory to store the encrypted passwords
an Arduino-compatible microcontroller with USB connectivity
We’ve been drowning in element recommendations from inspired hobbyists, so we figured we’d make the mooltipass v1 as easy as possible as well as then relocation from there. Given this gadget is established on Hackaday, we likewise desired future individuals to customize it, building totally new jobs based around these primary components. keep reading for our schematics…
For the core of the platform, we chose the ATmega32U4 from Atmel. It is the exact same microcontroller utilized in the Arduino Leonardo, enabling us to utilize the various libraries that have been established for it. In the final schematics, we’ll add an growth connector so individuals may link extra peripherals (we may switch to a 4 layers PCB at this point). The microcontroller’s USB lines are secured from ESD by the IP4234CZ6 from NXP.
For encrypted passwords storage, we discovered the cheap 1Mbit AT45DB011D FLASH which likewise has 2/4/16Mbits pin compatible versions. If our beta testers discover that 1Mbit is not enough, upgrading the mooltipass would be easy. A few visitors may already understand it, however when choosing a flash memory, special interest ought to be paid to the minimum amount of data that can be erased in the chip. If the flash doesn’t have an interior buffer (like the one we chosen does), the microcontroller should checked out a total chunk of data, customize the appropriate part as well as resend the customized chunk to the memory. provided the ATmega32U4 only has 2.5KBytes of RAM, this may have been problematic.
Finding a smart-card that might offer the preferred safety and security functions wasn’t the problem, however discovering a provider that might send us fairly low quantities (<1M) was. We did, however, discover the rather old AT88SC102 from Atmel, a 1024bits read/write secured EEPROM. It can be sourced for less than a dollar as well as our safety and security assessor didn’t item to this choice. It likewise utilizes an strange bus for communications (SPI-like with an open drain data line), which is why we utilized the N-Mosfet Q2. A hot-topic in the Google group was the screen choice. Although opinions were varied, we agreed on the core restriction that the selected screen ought to be at least 2.8″ as well as checked out quickly under bright light. High resolution as well as RGB wasn’t necessarily required, so as a very first try we’ve chose the OLED screen shown in the photo above (image taken from YouTube). After a number of weeks of searching for viable alternate OLED screens without any type of success, we’re currently thinking about making one more mooltipass version with an IPS LCD. Moreover, the present unusual 3.12″ diagonal implies we’ll requirement to have a customized resistive touch panel: the quotes we got for the capacitive ones were as well expensive. These elements options made the voltages electronics relatively simple. The whole service is powered by the ~5V coming from the USB, as well as the ~3.3V needed by both the flash as well as the screen is offered by the ATmega32U4 interior LDO regulator (~55mA @ 3.0 to 3.6V). The +12V likewise needed by the screen is produced by a $1 regulated fee pump DC-DC converter. If we had to utilize a traditional step-up, the element count (and cost) would be much higher. notice that we put a P-MOSFET in series with the latter as the output voltage when the DC-DC is not working is not 0V however VCC (here +5V). We likewise utilized one more P-MOSFET to switch the power supply going to the wise card. We utilized two resistor networks R6&R7 (easier to solder) as voltage dividers to transform our 5V signals to 3.3V. Fortunately, the ATmega32U4 can get LVTTL signals, so we don’t requirement level shifters to get the data coming from the 3.3v-powered flash memory. That wraps up the mooltipass schematics overview. If you have any type of suggestions, you can get in touch with the team in our dedicated Google group. Of program we’d like to hear general comments, please share them below.