FPGA Stepper motor control

Build to control stepper motors, with smooth rotation and ability to count steps exactly.

Verilog Code

Code to control a stepper motor driven robot car using an FPGA. Built to use an Artix 7 based BASYS 3 or CMOD A7. Tested with Vivaldo 2020.1. To build, open with Vivado, activate the appropriate contraint file by right clicking and selecting "Make Actve...". Update file "defines.v" to define the Macro for the chosen board.

Functionality

Communicates through SPI bus to accept commands, and give status, based on 8 byte command/status message, with start message type byte and one checksum byte. SPI message definition given in top module, with example of calling given in the spi_test.c test file.

Allows separate control for four motors with individual direction and step control, plus outputs for three signal LEDs, with PWM based pulsing. Variable speed control for either constant motion or for a fixed number of steps.

Hardware tested

Tested to control stepper motors though TLP281 optical isolators driving CNC Shield V3 with DRV8825, driving NEMA 17 motors.

Test code

Example Raspberry Pi based test harness, which could be used to base any car control system.

Wiring

SPI Bus to Pi

..............CMOD A7........PI Zero

o_SPI_Gnd.....U3 Pin 44......GPIO -- Pin 25

o_SPI_MISO....U7 Pin 45......GPIO 09 Pin 21

i_SPI_CS......W7 Pin 46......GPIO 08 Pin 24

i_SPI_Clk.....U8 Pin 47......GPIO 11 Pin 23

i_SPI_MOSI....V8 Pin 48......GPIO 10 Pin 19

Acknowledgements

SPI code based on SPI-slave code from Nandland.

Raspberry Pi test harness code uses pigpio.