openEMSstim

# Adding arduino components
Note that the openEMSstim board uses some of the arduino's digital pins, so what you have left is:

* D0 (digital pin)
* D1 (digital pin)
* D3 (digital pin)
* D11 (digital pin)
* D12 (digital pin)
* D13 (digital pin, currently used for internal LED, but you can opt out of that)
* A0 (analog pin)
* A1 (analog pin)
* A2 (analog pin)
* A3 (analog pin)
* A4 (analog pin)
* A5 (analog pin)

## Connecting new sensors to the board
Connecting new sensors should be straight forward. For instance if you have some [FSR sensor](https://learn.adafruit.com/force-sensitive-resistor-fsr/using-an-fsr) you would just connect it to a analog input (for instance A1). Do the same for all buttons (if these are digital you can connect to a digital port, e.g., D11), sensors, etc (input devices).

## Connecting new actuators to the board
Connecting new actuators needs a notice: the board uses MOSFETS and optocouplers which drain some of the power, this means if you add actuators like servos/motors, you should add a H-bridge/motor-driver with a separate power source (power for motors). This way you do not reduce the power of the openEMSstim components which could result in strange behaviors. 

## How to connect things to the board
Just some suggestions:

* solder female pin headers to the pins you want to use, now you can connect standard pin cables 
to it
* find an arduino without headers and solder a long header connector to it (not you can connect female headers on top to the unused pins)
* find an arduino without headers and a male connector under and a female connector on top (like the pin headers used in the arduino shields, essentially you are making your arduino into a shield) now you can use standard pin cables on the unused pins. 

## What if I run out of pins?
There's plenty of options to solve that (depends a bit on your design), here's a few:

* get a multiplexer (better make it a MUX/DEMUX) and use it to get more pins out of 2/3 pins.
* don't use the openEMSstim for anything else but EMS and just make it talk to other arduinos, there are several options for this:
	* I2C is a protocol for making digital components communicate
	* simply bit bang one port from one arduino into the other (e.g.., HIGH means do EMS, low means stop)
* did you run out of digitals but still have analogs? Use the analog pins as digital ports. 

### License and Liability

Please refer to the liability waiver (in documentation/liability_waiver.md).

Please refer to the license (in /license.md)