1. Introduction to Handshaking Communication with SSC-32U
Computer Integrated Manufacturing
© 2016 Project Lead The Way, Inc.

2. Table of Contents Definition Signal Compatibility Components
Optical Isolator
Resistors
Breadboards
Communications:
Lynxmotion to Lynxmotion
Lynxmotion to VEX®
VEX® to Lynxmotion
VEX® to VEX®
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© 2016 Project Lead The Way, Inc.

3. Handshaking
Handshaking is the process of communication that occurs between a robot and another piece of equipment in a work cell.
Computer Integrated Manufacturing
© 2016 Project Lead The Way, Inc.

4. Handshaking This is a very simple form of communication
A signal is sent from one machine to the robot or from the robot to a machine
Can also be between two robots or two machines
This signal is a simple “on” or “off” – in digital terms, a 1 (on) or a 0 (off). Did you ever notice that the symbol for an on/off switch is a “1” inside of a “0”? Check the computer you’re sitting at!
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5. When Is It Used? When a part feeder is empty
When a part is available for pick up or delivery
When an operation is completed
Communication between devices in a work cell is very important. A robot needs to know when to pick up a part, drop it off, or perform an operation. How many different forms of handshaking could be performed in the cell above?
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6. Signal Compatibility
When two machines talk, signals should be isolated to protect the machines from incompatible signals
Optical Isolators and Relays are used to do this
Some devices that we use operate use a 7.2 V signal, some use 5 V signals, and still others use a 3.3 V signal. What would happen if a 3.3 V signal is sent to a machine designed to receive a 7.2 V signal? It might not be a high enough voltage to interpret this as an “on” status. A 7.2 V signal is sent to a device designed to receive a 3.3 V signal could damage equipment. An interface, such as an optical isolator, between these machines is a more safe and reliable communication system.
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© 2016 Project Lead The Way, Inc.

7. Components: Optical Isolators
An Optical Isolator sends a signal as a light pulse from an LED (1 & 2) on the input side
The output side of the circuit senses the light and sends an electrical signal (4 & 6)
Optical Isolators, or Optoisolators, use a small Infrared, IR, LED connected to the input side of the circuit. When voltage is applied, the LED shines on an IR sensor on the output side. This sends an “on” signal without a voltage just like closing a switch. This action just completes the circuit.
4N25 Optoisolator 1 2 3 6 5 4
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8. Components: Resistor
A resistor is used to limit the amount of current to another component like the optical isolator
Red = 2
A resistor is a component that resists electrical current. We use it to limit the current going to the optical isolator. +
Red = 2 +
Brown = 0
Gold ± 5%
220 Ω ± 5%
Computer Integrated Manufacturing
© 2016 Project Lead The Way, Inc.

9. Components: Breadboards
A breadboard is used to:
Create a simple circuit without soldering
Keep wires as short as possible
Use as few wires as possible
Computer Integrated Manufacturing
© 2016 Project Lead The Way, Inc.

10. Components: Breadboards
The five holes of each row are electrically connected
On the breadboard shown the five holes in a numbered row are connected internally, but the groups of columns labeled a–e and f–j are not. Components such as a microchip must be placed to straddle the middle gap, or pins will be short-circuited.
Computer Integrated Manufacturing
© 2016 Project Lead The Way, Inc.

11. Components: Breadboards
The holes of each column of the bus bars are electrically connected
The pairs of columns on both sides of the breadboard are connected vertically and are called bus bars. These are not used for handshaking.
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12. Communication Between Devices
This circuit will be used to handshake between machines
Output
Device
Input Device
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© 2016 Project Lead The Way, Inc.

13. Basic Circuit for Communications
The five holes of each row are electrically connected
220 Ω
Signal (Yellow or White) 1 2 3 6 5 4 A C B E
(Not Connected)
Ground (Black)
Signal (Yellow or White)
(Not Connected)
Ground Black
4N25 Optoisolator
Computer Integrated Manufacturing
© 2016 Project Lead The Way, Inc.

14. Lynxmotion to Lynxmotion Communication
Example: When two robots have to perform a task at the same time or When one robot needs to wait for another to complete a task
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15. Lynxmotion to Lynxmotion
Communication Direction
Input A
Input A
In the example above, the Lynxmotion robotic arm on the left uses pin A as an input for the switch to start the program from the beginning, although the black wire must always face the outer edge of the SSC-32U board. The same robotic arm uses pin 15 as an output. Any output, 8-15, can be used for this purpose. The black wire, ground, must always connect to the pin closest the outer edge of the SSC-32U board. The Lynxmotion robotic arm on the right waits for this signal on input pin A in the image shown above.
Output 8-15
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16. VEX® to VEX® Communication
Example: When one machine completes an operation in a sequence, it can let the next machine know when it is safe to begin the next operation
In this example, a drill press and a grinder made out of VEX components are used.
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17. VEX® to VEX® Communication
From VEX
Cortex 1 +
To VEX
Cortex 2 +
Note that the bottom circuit is same as top circuit, except it is rotated 180 degrees
To VEX
Cortex 1 +
From VEX
Cortex 2 +
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18. VEX® to VEX® Communication
Communication Direction
Digital port
1, 2, 3
Digital port
1, 2, 3
Motor
port 1
Motor
port 1
Cortex 1
In the image above, the VEX Cortex on the left receives a input from the switch on digital port 1. Notes that any of the digital I/O ports can be used provided that it is configured within the ROBOTC program. NEVER USE A MOTOR PORT AS AN OUTPUT FOR COMMUNICATIONS. The same Cortex outputs a signal from digital pin 2 configured as a digital output in ROBOTC®.
The Cortex on the right receives a signal from the other Cortex on digital port 1 configured as a digital input in ROBOTC. The same Cortex on the right outputs a signal from digital port 2 to Cortex on the left. The Cortex on the left receives this signal on digital port 3. The Cortex on the right outputs power to the motor from motor port 1. This is the only use of a motor port in this example. All other connections are made using digital ports.
Keep the wires as short as possible, and use as few wires as possible when breadboarding. This will make it much easier to troubleshoot!
Arrows in the diagram above show direction of communication.
When using a VEX component to communicate with another VEX component, the signal to the second component gets inverted due to the optical isolator. You will need to compensate for this when developing a program in ROBOTC.
Cortex 2

19. Lynxmotion to VEX® Communication
Machines can be simulated with VEX components and can easily communicate with your Lynxmotion robotic arm.
Example: When a robot places a part on a conveyor, it can tell the conveyor when it is done
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20. Lynxmotion to VEX® Communication
From switch
To VEX
Cortex
From Lynxmotion +
Install male headers to adapt PWM cable
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21. Lynxmotion to VEX® Schematic
Communication Direction
Digital
port1
Input A
The red arrows denote direction of communication. Remember to keep the wires as short as possible, and use as few wires as possible when breadboarding. This will make it much easier to troubleshoot! X
Output 8-15
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22. VEX® to Lynxmotion Communication
Example: When a machine completes an operation, it can tell the robot that it is finished and that the robot may come and pick up the part. The example above might be a buffer or a grinder.
Example: When a machine is performing an operation, it can tell the robot when the operation is complete and it is safe to retrieve the part
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© 2016 Project Lead The Way, Inc.

23. VEX® to Lynxmotion Communication
Robotic Arm
From VEX
Cortex +
Install male headers to adapt PWM cable
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© 2016 Project Lead The Way, Inc.

24. VEX® to Lynxmotion Communication
Communication Direction
Digital port
1 and 2 X
Input A
In this example the VEX Cortex receives a signal on digital port 1. Digital I/O ports 1-12 can be used for this purpose. The Cortex outputs a signal to a Lynxmotion Robotic arm. Arrows denote the direction of the communication. The digital port 1 is used to output the signal and is configured as a digital output. The SSC-32U on the Lynxmotion robotic arm waits for this signal on input pin A.
Remember to keep the wires as short as possible, and use as few wires as possible when breadboarding. This will make it much easier to troubleshoot!
Programming is done in ROBOTC® by configuring a digital I/O port as an Output and then using the command SensorValue[]==1 and SensorValue[]==0 to send the signal. See the example in the Teacher Notes.
Computer Integrated Manufacturing
© 2016 Project Lead The Way, Inc.