Motion Drive 3.0 - User Guide

USB Modules

Provided as part of the Motion Drive 3.0 package are two USB modules. The software sends the drives signals out to these modules and collects inputs from the platform sensors via these modules.

They are numbered USB#1 and USB #2. Do not mix them up. Each one is already configured to perform a specific role in the input and output of the signals.

USB#1 is configured to send out the drive signals to up to three platform drives/motors.

USB#2 is configured to do several roles:-
1. It sends out the signal indicating whether the platform drive motor should go forwards or reverse (reverse signal).
2. It sends out the control signal for each DAC to enable the DAC to convert digital signals to analogue voltages.
3. It collects the state of the set of platform sensor switches for input to the PC.

Essential Information
Care and location of your USB Modules
Storage. The USB Modules are a delicate item of electronic circuitry. They are supplied to you in special anti-static protective wrapping and should be kept stored in that wrapping until ready for use in a clean dry place.
Location. They should be located in a suitable place on your motion base, where they will not be subject to physical or electrical damage, preferably firmly fixed inside a suitable elecrtical enclosure box of the type that can be purchased from component suppliers.
Installation. When handling and installing the modules, you should take care not to incur damage through careless handling and static electrical discharge. Make sure you use a suitable earthing method on yourself before and during handling. When connecting downstream components (DAC boards etc.), ensure that the modules are NOT powerd up by disconnecting them from the USB port of your PC.

How the modules work

Some basics
Computers work in digital format, being essentially vast switching machines. They run programmes and use data in digital form - a series of ones and zeros, representing a switch state of on and off. When we see letters and decimal numbers being displayed, inside the computer they are represented as a series of ones and zeros. Each one or zero is a bit. A group of bits is called a byte - be it a group of 16 bits or, more usually now, 32 bits.

Numbers can be interpreted by using binary, or Base 2, code (as opposed to what we are used to, which is decimal or Base 10 code). Instead of having columns of units, tens, hundreds etc, in binary the columns are units, twos, fours, eights etc. Instead of using the terms one and zero to say whether the bit is switched on or off, convention is that a bit is termed 'high' when on or one, and 'low' when off or zero.

The USB modules use groups of 8 bits, which are called Words. Conventionally the bits are numbered from 0 to 7 as shown:-

Bit 0, being the lowest value is called the Least Significant Bit (LSB).
Bit 7, being the highest value is called the Most Significant Bit (MSB).

So, using the 8-bit word system, we can represent any value from 0 to 255 (being the sum of all the bits if all are high). Zero would be shown as 00000000, and 255 as 11111111. An in between value might be 117 and shown as 01110101.

The USB Modules
Each modules has three ports (groups of input/output pins). Each group of pins has eight data pins and two voltage pins (+5V and Ground 0V). Following on from above, each port can show an 8-bit word according to the state (high or low) of each of the data pins. So we can input or output values between 0 and 255.

How the data is actually transmitted depends on the type of DAC board being used. The DAC should in any case be one that accepts 8-bit words.

Each USB module also has a type A USB socket. This is used to connect the module to the computer.

Unipolar DAC Operation
If the DAC configuration is unipolar then the output signal for the motor will be between 0 and 255, which will be converted to a control voltage of 0V to 5V maximum. In addition, there needs to be two other signals for the DAC. The first is the control signal, which is a single pin held low to allow new data into the DAC and held high to allow the DAC to output the analogue control voltage corresponding to the input it received. The second is the signal which dictates whether the platform drive is to go forwards or backwards. In unipolar mode this is done by a single pin held low for forwards and high for reverse.

Bipolar DAC Operation
In bipolar operating mode, the DAC can output either positive or negative voltages, for forward or reverse platform drive directions. This is achieved by using one of the 8 word pins as a forward/reverse indicator and the other seven pins for the amount of power. The pin used for signalling forward/reverse is the pin for Bit 7, the MSB. So, the maximum value of the other seven pins is now 127, giving an output control voltage of -2.5V to +2.5 V. Motion Drive allows for two different types of bipolar DAC, depending on how the bipolar range is set out within the 8 bits.

a) For the Classic Flight DAC (DAC mode = 2)
The Classic Flight DAC sets out the range of power values such that a decimal value of zero equates to full speed backwards and a decimal value of 255 equates to full speed forwards. Motion Drive does the conversion so that the correct decimal value is sent to the DAC to signal both direction and speed.

b) For Other DACs (DAC mode = 3)
Here the power and direction signals are kept separate. The power signal is expressed using the first seven bits and the direction signal is expressed using Bit 8, with backwards being set by that bit being high. Again, Motion Drive will send out the correct decimal value to signal motor speed and direction. If using a DAC other than the Classic Flight DAC, you do need to check that the signals required are inline with those sent by Motion Drive.

Connecting and Installing the USB Modules
To connect the modules to your PC, simply connect each module using a suitable USB cable (type A to type B) (not supplied), to the USB port of your PC. We recommend that you use a USB hub as this will allow you to place your PC away from the motion platform and reduces the number of cables around. If you intend to place your PC more than 2metres away from the platform (again a good idea) it may be necessary to buy a powered USB Hub, which will boost the signal to and from the modules.

On connection of the first USB module, your PC will start to look for the driver for it. You should go through the appropriate procedure to direct your PC to the driver located in the folder called USBDriver, which you transferred from the CD-ROM.
Once both modules are connected and the driver installed, you should check in Device Manager where you should see the USB modules on the list of USB devices.

It doesn't matter which USB module is connected to which USB port on your PC, the software will identify and allocate tasks to USB#1 and USB#2 correctly. It does matter what you connect to the ports of the USB modules though. That is dealt with below.

Having done the connection to your PC, you can open Motion Drive. On the main page you should see that the message titled Connection to Platform should say "Connected OK". Once that is seen close Motion Drive and disconnect the USB cables before proceeding with downstream connection.

Connecting Downstream equipment.
Downstream equipment in the word we shall use for the rest of the drive control system (DAC boards, motor control boards et al) and the sensors on your platform.

First it is necessary to understand the pin layout of the ports on each USB module. Each port has 10 pins. These are shown and their designations given below:-

	USB Pin	Use	Bit No.	Value (high)
	1	+5V	-	-
	2	I/O 8	Bit 7	128
	3	I/O 7	Bit 6	64
	4	I/O 6	Bit 5	32
	5	I/O 5	Bit 4	16
	6	I/O 4	Bit 3	8
	7	I/O 3	Bit 2	4
	8	I/O 2	Bit 1	2
	9	I/O 1	Bit 0	1
	10	GND	-	-

The Ports (Port A, Port B and Port C) are clearly marked on the board. Connection to the ports is achieved by using a standard IDC 10-way header plug and ribbon cable, both of which are easily obtainable from component suppliers.

What to connect to which Port on which Module?
The table below set out the configuration of each pin for each Port on both modules. You should connect your downstream equipment accordingly.
Reminder: check that you are connecting to the correct Port on the correct USB module - this matters if your platform is to work correctly. Check the modules are disconnected from your PC first.

USB Module #1 connections

USB Module #2 connections

For more details on Sensor terminology and configuration see the section on Sensor Configuration.

© Active Simulation Limited 2007

Motion Drive 3.0 User Guide version 1.0