Digilent 410-173-KIT - Manual (Page 5)

Cerebot 32MX4 Reference Manual
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operation of the TPS2051B can be obtained
from the data sheet available at the Texas
Instruments web site.
There are reference designs available on the
Microchip web site demonstrating both device
and host operation of PIC32 microcontrollers.
These reference designs are suitable to use for
developing USB firmware for the Cerebot
32MX4 board.
Pmod Connectors
The Cerebot 32MX4 has nine Pmod
connectors for connecting Digilent Pmod
peripheral modules. There are two styles of
Pmod connector: six-pin and twelve-pin. Both
connectors use standard pin headers with
100mil spaced pins. The six-pin connectors
have the pins in a 1x6 configuration, while the
twelve-pin connectors use a 2x6 configuration.
The six-pin connectors provide four I/O signals,
ground and a switchable power connection.
The twelve-pin connectors provide eight I/O
signals, two power and two ground pins. The
twelve-pin connectors have the signals
arranged so that one twelve-pin connector is
equivalent to two of the six-pin connectors.
The power connection is switchable between
the regulated 3.3V main board supply and the
unregulated input supply.
Digilent Pmod peripheral modules can either
be plugged directly into the connectors on the
Cerebot 32MX4 or attached via cables.
Digilent has a variety of Pmod interconnect
cables available.
See the “Connector and Jumper Block Pinout
Tables” section below for more information
about connecting peripheral modules and other
devices to the Cerebot 32MX4. These tables
indicate the mapping between pins on the
PIC32MX460 microcontroller and the pins on
the various connectors.
RC Servo Connectors
The Cerebot 32MX4 provides eight 3-pin RC
hobby servo connectors for direct control of
servos in robotics and embedded hardware
actuator applications. The connectors share
I/O pins with Pmod connector JC. Individual
I/O pins may be accessed through the JC
connector if they're not in use by a servo.
Refer to the PIC32 family data sheet for
information on how to access the I/O pins.
RC Servos use a pulse width modulated
signal, PWM, to control the servo position.
The 16-bit timers in the PIC32 microcontroller
have the ability to generate PWM signals using
the output compare registers. However, it is
also possible to use timer interrupts to
accomplish this same thing. Using timer
interrupts allows a single timer (ideally timer 0)
to be used to control the signal timing for all
eight servo connectors.
The servo connectors on the Cerebot 32MX4
board are intended to be driven using timer
interrupts rather than directly by the pulse
width modulators in the internal timers. This
frees the pulse width modulators for other
uses, such as DC motor speed control.
Digilent has a reference design available that
illustrates using timer interrupts to control
signal timing for the PWM signals to control RC
servos.
There are three power options for servo
connections: a common power bus (VU) for the
Cerebot 32MX4 and servos; separate on-board
power busses for the Cerebot 32MX4 (VU) and
the servos (VS); or an on-board power bus for
the Cerebot 32MX4 (VU) an external power
bus for servos.
For the first case above: Install the shorting
block on JP1 to connect the VS servo power
bus to the VU power bus. The servo power
bus is then powered from the same source as
the VU power bus. Powering a large number
of servos from USB power is not
recommended. USB power (J12 in the USB
Device Port, or USB Debug Port positions)
should only be used to power a couple of
servos to avoid exceeding the 500mA that a
USB device is allowed to use.
For the second case above: Remove the
shorting block from jumper JP2 to make the VS