Digilent 410-262P-KIT - Manual (Page 4)

chipKIT Motor Shield Reference Manual
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There are two Schmitt trigger buffered inputs on connectors J3, J6, J8 and J9 that bring motor speed
feedback signals to the controlling system board. The Digilent motor and gearbox have hall-effect
sensors arranged in a quadrature encoder format. These buffers have 5V tolerant inputs, when
operated at 3.3V.
The quadrature encoder signals are a pair of square waves whose frequency is proportional to motor
rotation speed and with the pulses 90

out of phase. You can determine the motor speed with the
frequency and motor rotation direction by the phase relationship between the two signals.
Stepper Motor Controller
The stepper motor controller has 4 output signals. It is composed of 4 open-drain transistor amplifiers.
Uno32
Pin #
PIC32
Pin #
Signal Notes
26 60 A: PMD0/RE0
27 61 B: PMD1/RE1
28 62 C: PMD2/RE2
29 63 D: PMD3/RE3
The stepper motor driver can be powered by either VIN, or an external power source connected to
J10. If connecting an external power source, JP5 should be removed to prevent shorting the stepper
motor voltages to the input voltage of the chipKIT board.
Servo Motors
The Motor Shield has 4 servo motor connections. They can be powered from VCC5V0 or an external
power source connected to J14. If connecting an external power source, JP6 should be removed. The
voltage of the power source can be measured on analog pin A11 via a resistor divider network (see
the schematic for more details).
Uno32
Pin #
PIC32
Pin #
Signal Notes
30 64 Servo1: PMD4/RE4 J16
31 1 Servo2: PMD5/RE5 J17
32 2 Servo3: PMD6/RE6 J18
33 3 Servo4: PMD7/RE7 J20
I
2
C Bus and Connectors
The Inter-Integrated Circuit (I
2
C) Interface provides a medium speed (100K or 400K bps) synchronous
serial communications bus. The I
2
C interface provides master and slave operation using either 7 bit or
10 bit device addressing. Each device is given a unique address, and the protocol provides the ability
to address packets to a specific device or to broadcast packets to all devices on the bus. Refer to the
Microchip PIC32MX3XX data sheet and the PIC32 Family Reference Manual for detailed information
on configuring and using the I
2 C interface.
The PIC32MX320 microcontroller on the Uno32 provides for two independent I
2
C interfaces. The
Motor Shield is designed to provide access to one of these interfaces, I 2 C #1 (SCL1, SDA1). I 2 C #1 is
accessed through the standard chipKIT Wire library. Connector J21 provides access to I 2 C port #1.