Pmod STEP Reference Manual

The Digilent Pmod STEP (Revision A) can drive either a 4-pin or 6-pin stepper motor.

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Features

  • Stepper motor driver for 4 and 6-pin motors
  • Can drive both motors simultaneously
  • Multiple LEDs to indicate signal propagation
  • Jumper for optional external power
  • 2×6-pin Pmod connector with GPIO interface

Functional Description

The Pmod STEP utilizes ST's four channel driver, a L293DD, to drive stepper motors at higher currents than a system board can typically provide from their logic outputs. External test point headers and LEDs are provided for easy testing and observation of the propagation of signals.


Interfacing with the Pmod

The Pmod STEP communicates with the host board via the GPIO protocol.

This Pmod offers headers for both 4-pin and 6-pin stepper motors. Stepper motors work by alternately energizing the coils to different polarities inducing the stepper motor to rotate.

4-pin stepper motors only work in the bipolar configuration, requiring that the two inputs on each electromagnetic coil are brought to the correct logic level voltages to induce current flow in the correct direction. The 6-pin stepper motor header on this Pmod can be oriented for either bipolar or unipolar configuration. The two extra pins on this header provide two positive power pins as a source of current for when an input on one end of a coil is driven to a logic low voltage level.

Pinout Description Table

Pin Signal Description
1 SIG1 Signal 1
2 SIG2 Signal 2
3 SIG3 Signal 3
4 SIG4 Signal 4
5 GND Power Supply Ground
6 VCC Positive Power Supply
7 SIG5 Signal 5/Output 1 for the Stepper Motor
8 SIG6 Signal 6/Output 2 for the Stepper Motor
9 SIG7 Signal 7/Output 3 for the Stepper Motor
10 SIG8 Signal 8/Output 4 for the Stepper Motor
11 GND Power Supply Ground
12 VCC Positive Power Supply

Any external power applied to the Pmod STEP must be within 4.5V and 36V; it is recommended that Pmod is operated at 5V.


Physical Dimensions

The pins on the pin header are spaced 100 mil apart. The PCB is 2.8 inches long on the sides parallel to the pins on the pin header and 1.38 inches long on the sides perpendicular to the pin header.


Additional Information

The schematics of the Pmod STEP are available here. Additional information about the four channel driver chip including specific timings can be found by checking out its datasheet here.

Example code demonstrating how to get information from the Pmod STEP can be found here.

If you have any questions or comments about the Pmod STEP, feel free to post them under the appropriate section (“Add-on Boards”) of the Digilent Forum.