599 Menlo Drive, Suite 100
Rocklin, California 95765, USA
Office: (916) 624-8333
Fax: (916) 624-8003
General: info@parallax.com
Technical: support@parallax.com
Web Site: www.parallax.com
Educational: www.parallax.com/sic
Parallax Servo Controller – USB (#28823) Rev B
16-Channel Servo Control with a USB Interface
Introduction
With the proliferation of servos used in technology today comes the obligation to manage multiple servos
each executing complex motions. The original Parallax Servo Controller (#28023) was designed to
remove the burden of driving the servo pulses from the controller and thereby expand the number of
servos that one controller could be expected to control. To that end the original PSC was quite
successful, but for some of the more complex applications writing a textual program to control many
servos executing compounded motions and actions can be tedious to say the least.
One way to make the whole application development process easier is to change the primary interface
from a keyboard (text-based code) to that of a mouse (visual based program). By adding a USB port to
the servo controller and providing the user with a free graphical user interface, a direct link between
mouse and servo is made. Move the mouse, the servo moves in real-time. Now the task of developing a
program to control intricate servo sequences becomes a palatable fun process.
The concept of the frame is introduced to help keep movements and sequences organized and
manageable. Sixteen servo positions and time delays make up a frame; two or more frames constitute a
sequence. Sequences may be stored as files on your PC’s hard drive to be retrieved for later use. Like a
movie, a sequence may be played, paused, stopped, or edited repeatedly until you get it just the way you
want it.
With animatronics customers in mind, the current PSCI software supports up to 128 frames. (Most
animal walking sequences require fewer than 8 frames.)
Packing List
Verify that your Parallax Servo Controller is complete in accordance with the list below:
Parallax Servo Controller – USB (PSCusb)
Shunt-Jumper
3-Conductor Cable
A to mini-B USB cable
Documentation (this manual)
Parallax, Inc. • Parallax Servo Controller USB – Rev B ver 3.4 (#28823) • 8/2006 1
Features
Each Servo is individually controllable: Position, rate, offset, and post delay.
Speed Control. Each servo may have any of 63 run-time changeable rates.
128 Frames supported though most sequences require far fewer frames.
Before You Begin
The processor used on the PSCusb requires 5 VDC which is supplied by the USB port. Servos
require far more power than the USB port can supply. Therefore you must use a separate
power supply for your servos. In general, servos require 4-7.5 VDC. Be sure that the servo
power source can supply ample current at the proper voltage and will not damage the
servos.
Getting Started
Locate and remove the PSCusb from its protective anti-static bag. It should closely resemble the image
shown in
Figure 1.
Figure 1: PSCusb – Rev B and mounting-hole detail
Mount the PSCusb using 4-40 screws (or equivalent). Ensure that none of the connections on the pcb
bottom are inadvertently shorted.
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Parallax, Inc. • Parallax Servo Controller – USB Rev B ver 3.4 (#28823) • 8/2006
Ensure the servo power switch on the Parallax Servo Controller is off, and then connect the power source
for the servos to the screw terminals observing proper polarity. Servos require more power than the USB
port can supply. For this reason, you must connect a separate power supply for the servos. See
2
.
figure
Figure 2: PSCusb, typical Connections.
standard servo
www.parallax.com
standard servo
www.parallax.com
B
Rev A
Ch15
Ch13
Ch11
Ch9
Ch7
Ch5
Ch3
Ch1
Ch14
Ch12
Ch10
Ch8
Ch6
Ch4
Ch2
Ch0
© 2005
S + -- + S
X2
* Note: Though a Rev A board is depicted here, the connections for the Rev B board are exactly the same.
Installing the PSCI software
Visit us at www.parallax.com and search for 28823. The download icon should be near the product
image. Once the program is downloaded, double-click on it and follow the installation instructions.
Parallax, Inc. • Parallax Servo Controller USB – Rev B ver 3.4 (#28823) • 8/2006 3
Using the PSCI software
Once installed, launch the PSCI software. It should start immediately and the following screen will be
displayed:
USB Drivers
The USB chip used by the PSCusb requires you to install drivers on your PC before using it. These drivers
are the same ones required by the Board of Education (with USB interface), so if you have already
installed these drivers, you needn’t repeat this procedure. The drivers are free and available from
www.ftdichip.com
chips provided, select the FT232BM entry. Under the Driver Package heading, select the file that
corresponds to your operating system and save this file to your desktop.
After downloading has completed, close your web browser and double click on the driver file you just
downloaded to start the installation process. Follow the prompts as directed. If you have any difficulty,
simply call Parallax Tech Support toll-free at (888) 99-STAMP, [888-997-8267]. Now you are ready to
use your new hardware.
4
. Simply go to their website and click on the “Drivers” button. From the list of FTDI
Parallax, Inc. • Parallax Servo Controller – USB Rev B ver 3.4 (#28823) • 8/2006
Selecting the USB Port
Unlike serial ports, USB ports are dynamic. That is to say that they are manifested when the PSCusb is
connected, and extinguish themselves upon disconnecting. If you are so inclined to witness this
phenomenon, simply open up the properties of the My Computer icon, then click on the Hardware tab,
then click on the Device Manage button. Once in the Device Manager, click on the small + sign next to
the Ports icon. Now, connect and disconnect the PSCusb while watching the Ports list. For proper
operation, connect your PSCusb to the PC USB port
To select a comm port, simply click on the File tab and hover the mouse over the Select Comm Port entry
to invoke the list of found comm ports. To choose a comm port, simply click on that comm port. If all
goes well, a message will report the successful opening of the comm port.
If you wish to confirm the presence of the PSCusb, you may then click on File->Get PSC version. If the
PSCusb is found, the version number will appear in the message window on the left side of the PSCI
screen. See below.
before launching the PSCI software.
Parallax, Inc. • Parallax Servo Controller USB – Rev B ver 3.4 (#28823) • 8/2006 5
Controls Description
To control the servos in real-time mode, connect your servos to the PSCusb and simply slide the power
switch on the PSCusb to the ON position. Now, moving the corresponding servo position slide bar in the
PSCI software positions the servo.
Offset
Not all servos are alike so the offset control allows you to vary the center point of each servo. This may
not matter too much for standard servos, but is very helpful when controlling servos modified to rotate
360 degrees.
Position
You may use either the slide control or the up/down arrows, or enter the servo position numerically to set
the servo position. Please note that by clicking on the numbers 2500, 1500, or 750, the servo position
will be set to that number. These numbers correspond to the width of the servo command pulse, in
microseconds.
Rate
Each servo may be set to a rate of rotation. Furthermore, each servo may have a different speed for
each frame. A servo rate of 0 will cause the servo to move as quickly as possible; it’s fastest rate. A
servo position of 63 will cause the servo to move to it’s destination position at its slowest rate. At speed
63, the servo takes about 45 seconds to complete a 180 degree motion.
Delay
When a frame is executed, as in animate mode, a servo command is sent to the PSCusb for each servo in
the order 0,1,2,3… After each servo command is sent, the delay time is observed before sending the
next servo command. The Delay parameter has no effect when operating in real-time mode.
Frame
The number to the right of the word “Frame” indicates the current frame.
Go to
The number to the right of the phrase “Go to” shows the frame number that will be jumped to when all
servo commands have been sent and all delays have been observed for the current frame. Note: no
servo commands are sent for servos that appear to be unused.
Animation Controls
Controls are provided to facilitate the creation, controlling, and editing of animation sequences. By
hovering the mouse over each control button (without clicking) a hint will pop up to help clarify the
purpose of the button.
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Parallax, Inc. • Parallax Servo Controller – USB Rev B ver 3.4 (#28823) • 8/2006
Creating a Sequence
Creating a sequence is easy. The following example shows you how to create a simple sequence.
Click on the 500 position for servo channel 0 and edit the delay for that channel to 500mS as shown.
Click the red circle (Record) to record the frame. Note: clicking the record button on the last frame of a
sequence caused the current frame to be copied to the next frame (this helps with animation sequences).
If you were to click the record button after editing an existing frame, the current frame would be
updated, and the next frame would not be disturbed.
Click the number 2500 for channel 0 and click the record button again.
Click the number 500 for channel 0 and click the record button again.
Click the number 1500 for channel 0, increment the Go to number to 0 and click the record button.
That completes one simple animation sequence. Now you may use the CD-like control buttons to run,
stop, and pause your animation sequence.
To save your sequence, simply click on Sequence->Save and specify a file name.
To retrieve your saved sequence, simply click on Sequence->Open and specify the filename.
Parallax, Inc. • Parallax Servo Controller USB – Rev B ver 3.4 (#28823) • 8/2006 7
Notes concerning the connection of the PSCusb to your stamp.
To those individuals using the Board of Education, Rev C:
1) The power source for the servos must be a separate power source from that of the
Board of Education.
2) Connect the three-pin cable from the PSCusb to X4, slot 15.
3) Ensure that the Vservo jumper selector, (between X4 and X5), is set to the VDD
position. Connect your servos to the 3 pin terminals provided.
4) To power your PSCusb, the power switch must be placed to the “2” position.
To all other users:
1) The power source for the servos must be a separate power source from that of the
5 VDC used to supply the on-board logic.
2) Connect the three pin cable from the PSCusb to: VDD (Red), VSS (Black), and the
white wire to your choice of I/O pin. VDD must be 5 VDC. Note: the idle state of
the serial line is 5 VDC.
Hardware Reset Pushbutton
The pushbutton on the PSCusb is connected to the reset circuit of the on-board microcontroller. Pushing
this pushbutton resets the microcontroller thereby resetting all parameters to their default values.
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Parallax, Inc. • Parallax Servo Controller – USB Rev B ver 3.4 (#28823) • 8/2006
Revision List
Hardware Firmware
--------------------------------------------------------------------------------------------------------------------------------
Rev A 1.4 (Internal prototype, never released)
No known issues with this version of firmware. Though the PSC – Serial was released with earlier version
of firmware, the PSCusb was only released with v1.4 firmware.
--------------------------------------------------------------------------------------------------------------------------------
Rev B 1.4 (Initial release)
No known issues with this version of firmware. Though the PSC – Serial was released with earlier
versions of firmware, the PSCusb was only released with v1.4 firmware.
--------------------------------------------------------------------------------------------------------------------------------
Note: your PSCusb is re-programmable. If your PSCusb firmware is not current, you may send it in to
Parallax for a free firmware upgrade. Your only cost is the shipping fee.
Liability Disclaimer
Parallax, Inc. is not responsible for special, incidental, or consequential damages resulting from any
breach of warranty, or under any legal theory, including lost profits, downtime, goodwill, damage to or
replacement of equipment or property, and any costs of recovering, reprogramming, or reproducing any
data stored in or used with Parallax products.
Parallax, Inc. • Parallax Servo Controller USB – Rev B ver 3.4 (#28823) • 8/2006 9
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