Shrinking microcontroller projects and arduinos with Attiny85 or digispark or digistump with V-USB [quick start digistump tutorial]

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Small form factor attiny85 with Virtual USB (digistump) -Shrinking arduinos

AVR microcontrollers and arduino ide's are very popular among electronics hobbyist for their ease of usage and faster learning curves. It is much easier to learn programming microcontrollers with an arduino ide and typical prototyping boards like arduino uno or mega. But it is much nicer to move on to simple and cheaper solutions which provides the same power and lower cost. This can be achieved by using attiny85 or atmega328 along with a bunch of components.


Recently i came across a nice product from digispark (interestingly the schematics etc are available to the public) It is based on an attiny85 which is sufficient for doing many small tasks which fits in a 6k footprint, for e.g a simple temperature logger. More interestingly it uses V-USB , a virtual, slow usb using software on avr micros (also on PIC as well). More on V-USB can be read here  The unique micronucleus bootloader allows us to program it directly from the USB port and also allow us to use all most all the available pins on the attiny85.  Interestingly all these can be built from scratch (see e.g at this instructable). See below for a schematic (Very minimal!)

Digistump, tiny Arduino Schematic

Quick start guide for using and Programming a digispark/ digistump

The arduino ide is similar but is slightly different in its upload process (hex file to micro controller).

Basically you have to download the interface from here. For linux users it is a bit tricky as you need a udev rule (else you wont be able to program/ upload sketches)

AFter setting up the ide, it is straight forward to upload the sketches to attiny85 on digistump. Only difference here is , you need to connect the device to usb port after you have pressed the sketch upload button!

I started testing it with the blink sketch (it is slightly different in terms of digital pins, so choose the example sketchs specific to digispark from the ide interface). Further more it is also possible to compile the hex files directly using a make file and upload it direcly using the commandline version of the micronucleus application. More on it on a next post. This could be good way to learn more on programming avrs directly by using avr gcc as it can save some program space and goes fine with the memory constrains. 

I am planning to make a simple password manager with an attiny85. This could bea simple version of mooltipass. There are similar projects which can be seen here