The Old Board

As mentioned, all four joints use NEMA 17 and 11 steppers, which are controlled by four A4988 boards with the 1/4 step pins connected high. When developing the robot these were simply wired up on a bread board as follows:

This works as needed, however for the custom control box, there needs to be a more compact and elegant solution.

The Longrunner CNC Shiel

For this the Longrunner CNC shield was used (https://www.amazon.ca/gp/product/B06XJKVLG3/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1). This Arduino shield works perfectly as it has 4 stepper controller inputs (X, Y, Z , made for a 3-axis CNC and an auxiliary clone). To access the fourth axis (labelled A), they connect to digital pins 12 and 13 on the Arduino for step and direction. I also purchased an Arduino Mega to accommodate the larger sketch sizes required by the ros_serial library to interface with the MoveIt publisher (coming next). Here is the new circuit: