The Knob

All boards come preloaded with my latest firmware, have been tested for proper operation and are ready to go (except DIY option). PWM on the DIR-pin is enabled.

You will also get a little adapter to convert from the standard 6pin 0.1in ISP header down to the smaller 2mm one used the circuit board. You need to tilt the adapter sideways and apply a bit of pressure to ensure all pins make contact.

Updates:

• September: Future stock will only be available as DIY kits.
• May 12th: Added scripts / patches to optionally create an Arduino-IDE 'sketch' (linux/mac)
• April 22nd: Upgraded to ATtiny85 !
• March 26th: Sent out some more boards.
• March 25th: Prepare to receive your Knob.
• March 22nd: The circuit boards have arrived. I haven't picked them up yet though.
• March 22nd: I was informed that the circuit boards were shipped on the 20th. They might arrive today.
• March 21st: It should work fine with the RaspberryPi, once the console login on its serial port has been disabled (google knows more). Might require an additional 3.3V regulator, as the 3.3V pin of the Pi only provides 50mA.
• March 13th: I was informed that production of circuit boards has finally started.
• March 11th: Sent a loud 'ping' to the PCB manufacturer about the delay.
• March 9th: Received the encoders today. They look & feel pretty good. I added a picture as well.
• If you have any special requests ("I want it unassembled", "don't solder this or that"), drop me a message. Please include your order number.
• Once all fundraiser orders have been fulfilled, the remaining bare circuit boards will become available >>here<<.
• I've eliminated single resistors in favour of resistor packs. That should shave off a lot of assembly time.
• I've updated the micro controller to an attiny45. More free code-space and RAM for you!

With the latest additions to the firmware (velocity, PWM output to control something else directly, like a logic-level MOSFET...), the remaining FLASH memory of the attiny25 was getting a bit low. Not seriously low, but below 35%. Now with a total of 4kb of code-space (about 2.5kb free, if you use my firmware), there should be enough room for even the wildest and strangest ideas.

• The fundraiser has passed the minimum order. Great!

What is it?

First of all it is a very small printed circuit board, combining a mechanical rotary encoder with a micro controller. The micro reads the encoder, counts ticks and direction and registers the state of the push-button. Simple functions are provided to query the state of the encoder, whether a button has just been pressed or released and how many ticks have occurred. Only about 1.5kb of code-space is used.

What is it good for?

• Quickly add a rotary knob to a project with a free serial port
• Throw in a cheap USB serial adapter & use the supplied perl script for volume control on your linux machine (KDE4, kmix)
• Add a few lines of code to get step / direction output and use it to test some stepper motor controllers
• Use it as a PWM generator to control something else, maybe a simple lamp
• Getting started with rotary encoders

Partial list of parts:

• ATtiny85 (upgraded from ATtiny45, upgraded from ATtiny25)
• TT EN11-HSM1AF15 - almost identical to the one shown on the photograph

Specs:

• Dimensions: 23.5 x 23.5mm
• Mounting holes: M2 (approx. #1-72 bolt), spaced 18.0mm
• Supply voltage: up to 5V
• ISP connector uses 2.00mm raster
• Serial data output: defaults to (9600,8,N,1)
• Step / direction output easily implemented in firmware

The demo firmware currently provides functions for:

* read the current state of the push-button
* check for button-pressed event
* check for button-released event
* read the amount of accumulated ticks (+/-) in a small buffer
* read the velocity - updated 10x per second
* optional automatic coarse/fine mode (velocity dependent)
* soft-uart for sending numbers, ascii characters and strings
* optional 30kHz PWM output on the 'DIR' pin
* interrupt code for time / delay, encoder reading in background
* simple compile script (linux)

The supplied compile bash-script makes used of an installed version of the Arduino-IDE (1.0.4), so you shouldn't have any issues with getting the right version of the avr-gcc compiler for your distribution. Just adapt the PATH variable used in the script according to your system.

Linux / mac (maybe) users will get the benefit of a couple of scripts / patches that allow you to create an Arduino-IDE 'sketch'. This requires the MIT attiny code as well. You can download a modified version of the Arduino-IDE including the firmware / examples here.

I've added detailed descriptions for Microsoft detainees on how to migrate the code to the Arduino-IDE. All of this will have to be done by hand and should be done in 5 minutes.

Recommended to fully enjoy the board:

• AVR ISP programmer (avrispmkII, usbtiny, usbasp, Arduino-ISP ...)
• An up-to-date Linux installation
• Installed Arduino-IDE (used to get easy access to a working avr-gcc compiler)

Documentation:

• Code
• Layout files
• Getting started writeup

What happens if this fundraiser is successful

• I will instantly order the circuit boards and all parts, which will take a while. Expect at least 2-3 weeks for that alone.
• Once I have all the parts, I will start assembling boards. As I'm not a robot, this will take some time too. I will send them out as I finish them, unless I'm struck by lightning or equally unpleasant things...