Communications
A diagram of the communications between our ACV (boat) and CVC (controller) is shown below. Below the diagram you will find more detailed descriptions of the communication networks used in our project.
CVC to ACV
Two Xbee radios handle the RF communication between our controller, our boat, the atolls, and the rest of the fleet. An Xbee PIC (that is, a PIC largely dedicated to communications through the Xbee radio) on our CVC and on our ACV transmit data to and receive data from the Xbee over UART (9600,N,8,1).
Within the CVC
On the CVC, the Xbee PIC also sends commands to a PIC dedicated to updating the display servos over UART (9600,N,8,1). Distinct message headers were used to differentiate between messages intended for the Xbee radio and commands directed at the servos PIC.
Onboard the ACV
On the ACV, the Xbee PIC also sends commands to two PICS that drive our motors and flag servos over UART (9600,N,8,1). Distinct message headers are used to differentiate between messages intended for the Xbee radio and commands directed at the motor driver PICs.
Because we did not program the RFID Reader and the Security Controller, we could not configure their UART protocol and therefore need separate UART channels to receive transmissions from each device. One PIC, programmed in Assembly, listens to the UART transmit line of the RFID reader and interpreted any card scans. Another PIC handles all necessary UART communications with the Security Controller.
An SPI network unites the three PICs on the ACV. The Security Controller PIC is the master of the SPI network, with the other two devices configured as slaves. When the RFID PIC receives serial number data over UART from the RFID Reader, it sets a line high to indicate that it has a scanned serial number to send. The Security Controller PIC then extracts this data from the RFID PIC over SPI, obtains a security key from the Security Controller over UART, and then sends the serial number and security key to the Xbee PIC over the SPI network. At this point, the Xbee PIC interprets this data and decides what actions to take.
