Paranoia abounds! well maybe a bit – we are in a situation where we don’t trust our tools – especially our crypto tools – this project is an attempt to create a cheap open source entropy generator that’s open enough that one can verify and trust it.
We’ve based our design on an existing platform – our Cheap RF system – mostly because it’s cheap to build, we had existing hardware, and had just finished bringing up a USB stack for it
Our simple device is a USB stick, it is open source hardware, you can build your own, runs open source firmware – and you can physically open it to make sure that what’s inside is what you expect. With an external programmer you can also program it with your own firmware.
We generate ~350kbits per second of entropy packaged at ~7.8 bits/byte – if you use the entropy data at a lower it accumulates and we quickly approach 8 bits/byte.
OneRNG – Open Random number generation project - [Link]
Espruino Pico has everything you need pre-installed. It can be used from virtually any device with a USB port so you can get started in seconds.
ajoyraman posted a tutorial on how to make a DIY USB-matchbox oscilloscope, an instructable here:
In order to economize on the cost of an enclosure while still providing an aesthetic unit the Aj_Scope2 is enclosed in a large size cardboard matchbox enclosure.
The USB connection to the PC is on one end while the Audio-Jack for the signals to be monitored is on the other.
A ‘Busy’ LED is provided on one corner at the top and a ‘Reset’ switch is provided diagonally opposite.
The ‘Reset’ switch provides a restart of the micro-controller is the worst-case of hang-up. This typically occurs when the operator selects a trigger threshold which is out of limits with respect to the waveform being observed. If the Aj_Scope2 is operated correctly this switch is seldom used.
DIY USB-Oscilloscope in a matchbox - [Link]
by Naomi Price & Martin Rowe @ edn.com:
USB data-acquisition modules offer good value and ease of use, which makes them an attractive choice for manufacturing test. But before you use the modules in a manufacturing test system, you need to take steps to protect them. During manufacturing test of circuit boards or subassemblies, a defect in an assembly may result in a condition that damages a data-acquisition module.
Test Ideas: Protect USB measurement circuits - [Link]
A USB port is a great power source for charging a single cell Lithium-Ion battery. It is capable of supplying a maximum of 5.25V and 500 mA. The circuit above is a USB powered single cell Li-Ion battery charger. LM3622 is used as the controller. This special purpose IC has a precise end-of-charge control and low battery leakage current about 200nA. S1 and S2 select the low voltage detect enable/disable. The low voltage detection is handy for conditioning a deeply discharged battery with a low current stage, to prepare it for the full charge cycle.
LM3622 Li-Ion USB Battery Charger - [Link]
BreadBoardManiac have been making some cool prototyping boards and accessories like their thin, double-sided, BiscuitBoard and CakeBoard that can be physically mounted onto the LEGO brick system, they even produce a special breadboard made of wood! Along with the accessories is a wire stripping gauge that allows you to accurately bend wire interconnects and cut them to the correct length so that they all line up neat and tidy, flush with the surface of the solderless prototyping board. The finished wiring looks like a work of modern art rather than the messy rats nest effect that you normally get with flying leads. You have probably already worked out that these people are passionate about breadboarding.
Neat Breadboard Connector - [Link]
Brian Dorey made this DIY USB to RS485 adapter, that is available at Github:
We looked for a full-duplex ready-made adapter but all the ones we found are only half duplex devices and as we needed to be able to supply 12 volts via the RJ45 connectors on the slave boards we decided to make our own USB to RS485 full duplex adapter using a USB converter chip from FTDI.
The board uses an FT230X with an RS485 converter chip which outputs to a set of header pins and also an RJ45 socket.
The new adapter board can supply power to the slave devices through the USB port or can be powered from an external supply by removing a power selector jumper. The board also has an on board 120R terminator resistor with selection jumper and LED’s to show serial activity.
USB to RS485 adapter - [Link]
Alan Parekh @ hackedgadgets.com writes:
This video was going to be a repair of this Portable USB Charger but as it turns out there wasn’t anything electrically wrong with it. It didn’t work out of the box but I think that must have been caused by some oxidation on the USB contacts. It seems to work like a champ now. The control chip for the DC/DC converter looks to be this DHMF chip. I have never seen the swoop logo before and can’t seem to find any data on this 5 pin device though. It is probably similar to the LT1302 (PDF) that the Adafruit MintyBoost uses. The efficiency of this circuit doesn’t appear to be as efficient as a proper one built using the LT1302 though since when drawing 500mA from the output it can maintain very close to 5 volts out (2.5 watts) but needs an input of 3 volt at 1.3 amps to do it (3.9 watts). This gives us an efficiency of about 64%, the graph from the datasheet of the LT1302 indicates that it could perform at about 86% under these conditions.
Portable USB Charger Teardown - [Link]
One basic need of a computer scientist is to measure the power that a USB device drains off the PC. This device is plugged between the PC and a USB device and displays the current on an LCD. For currents under 100mA it is displayd in 0.5mA steps and 1mA steps for currents over 99.5mA. It is built with an AVR programmed in assembler.
USB Power Monitor - [Link]