Datasheet

proper terminals. Alternatively, connect your DC motor(s) to the screw terminals (J4 and/or
J5) and if using encoders, wire signals to J7/J13. Connect motor power (16V max) to the
Motor Power screw-terminals (J6). Motor direction is controlled by setting myRIO “DIR0” or
“DIR1” pin HIGH or LOW and speed/torque is controlled by setting the duty cycle on the
myRIO PWM0 and/or PWM1 pins. The A4973 driver has been configured for a 1.5A max
current (at 100% duty cycle). Motor voltage and current can be monitored by reading the
myRIO analog inputs according to this table:
MXP Pin#
Name
Motor Signal
3
AI0
Motor 0 Current
5
AI1
Motor 1 Current
7
AI2
Motor 0 Voltage
9
AI3
Motor 1 Voltage
*Hobby Servo Motors* J10 and J11 are standard 3-pin hobby servo motor connectors and
will work with most popular servo motors with no modification. The PWM control signals are
connected directly to the myRIO PWM pins on the MXP port, so no additional wiring is
required other than providing external power to J8.
*Stepper Motors* A single standard 4-wire (bipolar) stepper motor can be controlled by
wiring each winding to one of the motor terminal blocks (J4 and J5). Typically, the two
windings are controlled and coordinated using a variety of patterns from simple ON/OFF
(100% duty cycle and 0%) in quadrature between the two windings (Full Step) to “Half-Step”
control to help smooth transitions and increase positional resolution, to microstepping, where
many levels of PWM are used to approach a sine/cosine control of the windings. There are
many resources for help choosing the best control approach. This applications note from ST
Micro is one example, and the datasheet for the Allegro driver device used the board is also
a good resource.
Please visit the myRIO Community Website for example code and project ideas.