# Introduction

The 640 board is used to drive up to 6 DC motors and 2 Servo motors.

## Getting started
## Board layout
## Setup
### Attaching the power
### Attaching a Servo
### Attaching a motor
### Attaching an RC receiver

# Programming the 640

## Python

### Introduction

The Python libraries for the 640 board and some example scripts are available via our GitHub repository. To install them open a terminal window on your Raspberry Pi (unless you are running with only the command line) and enter the following:

``` bash
$ git clone https://github.com/darkwaterfoundation/darkwater_python_640.git
```

### Example scripts

Now that you have downloaded the 640 libraries you should have a new directory called *darkwater_python_640, so let's move into that directory

``` bash
$ cd ./darkwater_python_640
```

If you list the files in this directory, you should see a few test scripts

``` bash
$ ls -al
```

#### 640motortest.py

This script will start each motor port, in the forwards direction, in turn from left to right and then do the same backwards. To run the script enter the following:

``` bash
$ python 640motortest.py
```

#### 640servotest.py

This script will move any servos connected to the servo headers left, then center, then right. To run the script enter the following:

``` bash
$ python 640servotest.py
```

#### 640steppertest.py

This script divides the 6 motor ports into 3 stepper motor ports. Motor 1 and 2 will be stepper 1, motor 3 and 4 will be stepper 2 and motor 5 and 6 will be stepper 3.

Each stepper will be moved forwards and backwards through 200 steps when the test script is run:

``` bash
$ python 640steppertest.py
```

### The 640 board API

Now you know everything works, it's time to write your own scripts. So create a new python script in your editor, within the *darkwater_python_640* directory with a memorable name and add the following lines to import our libraries:

``` python
import time
from darkwater_640.darkwater_640 import dw_Controller, dw_Motor, dw_Servo
```

#### Create a controller

The **dw_controller** object controls access to all the elements on the 640 board, so the first thing we need to do is create a controller - we pass in the address of the 640 board as a parameter - the default address is 0x60

``` python
dw = dw_Controller( addr=0x60 )
```

Now that we have the controller created, we can access all the connectors on the board.

#### Select a Motor

There are 6 motor ports on the 640 board numbered 1 to 6 from left to right (with the ports facing you ).

If we want to control a motor on port number 1 then we need to request the motor object for that port from our controller - this is very easily done with a single line

``` python
m1 = dw.getMotor(1)
```

#### Motor driving

There are two main commands that you can give a motor - to move in a direction and to stop. We'll start with the main command to stop the motor

``` python
m1.off()
```

We can also stop the motor by using the second command and passing a speed of 0

``` python
m1.setMotorSpeed(0)
```

The **setMotorSpeed* command allows you to specify the speed of each motor - there are two different speed ranges the first goes from *-255* to *255*, the second from *1000* to *2000*. 

If you are familiar with radio control vehicles and ESC motors then you will recognise the second range.

For now we'll concentrate on the first range.

To get your motor going forwards at full speed you should set its speed at 255

``` python
m1.setMotorSpeed(255)
```

To get your motor going backwards at full speed you should set its speed to -255

``` python
m1.setMotorSpeed(-255)
```

The numbers from 0 to the maximum in each direction will drive the motor at a slower speed, so for half speed forwards we'd use

``` python
m1.setMotorSpeed(125)
```

And for a slow speed backwards we can use

``` python
m1.setMotorSpeed(-50)
```

##### Alternate speed range

If you plan to move from a DC driven robot to an ESC motor powered robot then it makes sense to use the same conventions that will work on both, so you can also use the 1000 to 2000 speed range with the 640 board

To get your motor going forwards at full speed you should set its speed to 2000

``` python
m1.setMotorSpeed(2000)
```

For full speed reverse you should set the speed to 1000

``` python
m1.setMotorSpeed(1000)
```

And to stop the motor we can set the speed to the mid point which is 1500

``` python
m1.setMotorSpeed(1500)
```

As before, any number between 1500 and the maximum in each direction will drive the motor at a slower speed, so for half speed forward you'd set the speed to 1750

``` python
m1.setMotorSpeed(1750)
```

and half speed in revers would be 1250

``` python
m1.setMotorSpeed(1250)
```

#### Select a Servo

#### Servo control

## Node.JS

### Introduction
### Import libraries
### Drive a motor
### Motor speed
### Servo control

## C++

### Introduction
### Install prerequisites
### Drive a motor
### Motor speed
### Servo control
### PPM integration

## Expanding the board

### Adding an expansion board