From 99ef9a4f4ab0494be2647c5510ed986b22e3faf1 Mon Sep 17 00:00:00 2001
From: shrkey <barry@shrkey.com>
Date: Tue, 27 Sep 2016 21:25:39 +0100
Subject: [PATCH] servo docs

---
 640.md | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 47 insertions(+), 1 deletion(-)

diff --git a/640.md b/640.md
index 2bc7670..7b4682f 100644
--- a/640.md
+++ b/640.md
@@ -3,7 +3,15 @@
 The 640 board is used to drive up to 6 DC motors and 2 Servo motors.
 
 ## Getting started
+
+![640](/images/640-450.png)
+
+Welcome to the 640 board - this guide will describe all the features of the 640 board and show you how to control up to 6 motors or 3 stepper motors very simply.
+
 ## Board layout
+
+
+
 ## Setup
 ### Attaching the power
 ### Attaching a Servo
@@ -179,10 +187,48 @@ m1.setMotorSpeed(1250)
 
 #### Select a Servo
 
-There are two servo ports on the 640 board
+There are two servo ports on the 640 board. They are numbered 1 and 2 with number 1 to the left hand side and number 2 the closest to the motor ports.
+
+You select a servo in the same manner as you select motors, by requesting a servo object from the controller - to select the first servo we use:
+
+``` python
+s1 = dw.getServo(1)
+```
 
 #### Servo control
 
+Once you have a servo object there are currently three commands you can run.
+
+##### off()
+
+The off command will switch off your servo and stop any signals being sent to it.
+
+``` python
+s1.off()
+```
+
+##### setPWMuS( *microseconds* )
+
+This command will allow you to set the PWM pulse to the Servo in microseconds. 
+
+Most standard servos use a parameter value of 1000 for fully counter-clockwise, 2000 for fully clockwise, and 1500 for the middle - though you may have a wider range on your servo, so you should check the technical documentation for it to get the finer details.
+
+``` python
+s1.setPWMuS(1500) # middle
+s1.setPWMuS(2000) # fully clockwise
+s1.setPWMuS(1000) # fully counter clockwise
+```
+
+##### setPWMmS( *milliseconds* )
+
+This command allows you to specify the PWM pulse in milliseconds rather than seconds.
+
+``` python
+s1.setPWMmS(1.5) # middle
+s1.setPWMmS(2.0) # fully clockwise
+s1.setPWMmS(1.0) # fully counter clockwise
+```
+
 #### Select a Stepper motor
 
 You can control up to 3 stepper motors with the 640 board - each stepper motor uses two motor ports for 4 wire stepper motors and three motor ports for 5 wire stepper motors.