Cerebot MC7™ Board Reference Manual
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
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A fixed reference voltage of 2.33V is used to set the comparator threshold for determining an over current
condition. This sets the comparator to signal an over-current condition at 6A. If the current through any half
bridge exceeds ~6A, an interrupt can be triggered on INT1.
7
CAN Interface
The Controller Area Network (CAN) standard is a control networking standard originally developed for use in
automobile systems, but has since become a standard used in various industrial control and building automation
networking applications as well.
The dsPIC33 microcontroller used on the Cerebot MC7 contains a CAN network controller. This CAN controller in
combination with a Microchip MCP2551 CAN transceiver allow the Cerebot MC7 board to operate on a CAN
network. Refer to the dsPIC33FJXXXMCX06A/X08A/X10A Data Sheet and the dsPIC33F Family Reference Manual,
plus CAN network documentation for information on operation of the CAN controllers and CAN networking in
general.
There is no standard connector for use with CAN networks. The Cerebot MC7 board provides a 2x6 pin header
connector, J9, for access to the CAN signals. Refer to the schematic for the Cerebot MC7 board for information on
the connectors and signals. Digilent 6-pin or 2x6 to dual 6-pin cables can be used to daisy chain Digilent boards
together in a CAN network. A Digilent 6-Pin cable in combination with a Digilent PmodCON1 Screw Terminal
Connector module can be used to connect the Cerebot MC7 board to other network wiring configurations.
The CAN network standard requires that the network nodes at each end of a network provide 120 ohm
termination. The Cerebot MC7 provides the termination resistor and jumpers to enable/disable this resistor
depending on the location of the board in the network. Jumper JP6 is used to enable/disable the termination
resistor. Install a shorting block on the jumper pins to enable the termination resistor, or remove the shorting
block to disable the termination resistor.
8
RC Servo Connectors
The Cerebot MC7 provides eight 3-pin RC hobby servo connectors for direct control of servos in robotics and
embedded hardware actuator applications. These connectors are on the upper right side of the board.
The servo connectors S1-S8 are connected to PORTD bits 0-7 in the dsPIC33F microcontroller. These signals also
appear on Pmod connector JC, and PORTD bits 4-7 are also used by the on-board LEDs. Devices connected to
Pmod connector JC may interfere with operation of servos on the servo connectors, or alternatively, devices
connected to the servo connectors may interfere with operation of a device connected to JC. Refer to the
dsPIC33F data sheet for information on how to access the I/O pins.
The three pins on a servo connector provide the control signal, power and ground. There is no standard color
coding for the wires on hobby servos. They are wired so that the center pin of the connector provides power to the
servo. Because of this configuration with power on the center pin, the servo will not be damaged if it plugged in
backwards. Generally, the center pin will have a red wire. On many servos, the ground pin will have a black wire
and the signal wire will be a light color such as white or yellow. Not all servo manufacturers adhere to this
convention however. The servo connectors on the Cerebot MC7 board are configured so that the signal pin (pin 1)
is on the left side (toward the center of the board) and the ground pin is on the right side (toward the board edge).
