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Backplane General Overview

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David Walker-Howell edited this page Aug 5, 2019 · 1 revision

Backplane General Overview

General Description

The backplane on the Perseverance AUV deals with the communication process and data packaging/routing of various sensors and actuator that help the AUV navigate. Primarily, the backplane allows the on-board computer to communicate using serial communication to the sensors and actuators. Currently, the backplane only supplies the pressure depth transducer data to aquire the depth of the vehicle.

Communication Protocol with Backplane

Communication between the computer and backplane is performed through a single serial communication port. In general, the computer will send a "request" message to the backplane to either 1) receive data from a sensor connected to the backplane (such as pressure sensors) or 2) request that the backplane send some control input to an actuator (such as weapon solenoids). In either case, the backplane will send a message back either with the requested data or confirmation that the actuator operation was performed.

Making a Request to Backplane

To make a request to get backplane data, a 3 byte message must be sent to the backplane. Below is a description of how the message is formatted.

  • Byte 1: <0xEE> This is the header byte that must be the first byte of any request message sent. It is how the backplane will know to begin reading the next bytes which carry the request message.
  • Byte 2: The second byte corresponds to the type of request being made. These are predefined depending on what sensor or actuator you are trying to make a request about.
  • Byte 3: The third and last byte is the termination byte which is what the backplane uses to confirm the entire message was read properly. The termination byte also depends on what you are attempting to request.

You can find the messaging structures for requests (and responses) in the docs folder under [Backplane RoboSub 2019 Communication Frames Rev. 9.1.xlsx].

Note: I have written software that handles the requests and responses. However, it does not implement all of the possible requests currently.

The Sensor and Actuators Connected to Backplane

Again for finding out about what the message structures are for various sensors and actuators, refer to the document mentioned above.

Interrupts, Sensors, and Actuators

All Critical Interrupts are sent from backplane

  • Kill Switch Interrupt
  • Leak Interrupt
  • Depth Interrupt
  • Sensor Interface Board (SIB) General
  • Weapons Control Board (WCB) ESC[1,8]
  • Backplane Current
  • Backplane Auto

Weapons Commands

  • There are 13 Solenoids that can be commanded to actuate for different weapons. All of which use the WCB board.
  • Once a request is made to one of the weapon solenoids, a weapon command confirmation will be sent from the backplane to the computer.

Sensor Interface Board (SIB) data requests

  • External and internal pressure
  • Internal temperature

HYDRAS

  • Acoustic data from the hydrophones
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