This circuit is mainly designed to serve as a tool for shooting pictures for focus stacking macro photography. But it is actually a simple stepper motor driver panel which can be used for other purposes where we want to program the movement of a stepper motor.

Focus stacking is a nice technique to increase the depth of field of a -typically macro, but it can also be a landscape- photo. One takes several images focused on a different spot of the field of interest and then combines the "sharp parts" of the images with a dedicated software (e.g. Adobe Photoshop). This will create an image where every single pixel is in focus.

The working principle of this circuit is that one can program the necessary parameters, and then the circuit will drive a stepper motor (linear actuator) and trigger the shutter of a camera (it is tested for Sony A6000). Since this specific application focuses on macro photography, we can decide whether we put the camera on the linear actuator, or the object (e.g. a bug) itself. Then, by moving the linear actuator and taking pictures we get the pictures for the focus stacking. Finally, we just need a software to compile the set of images into one single picture.

The code I developed works in the following way:

1. Upon startup, the user can do a homing or can skip it
2. The user has to enter the chosen aperture (f-number, written on the lens)
3. The user has to enter the chosen magnification (can be read from the lens if it is a macro lens, or can be calculated)
4. The code calculates the depth of field (DOF) and suggests a step size (DOF/2) for the stacking
5. The user can optionally override the suggested step size with a unique value
6. The user has to move the carriage to the desired finish point, the point where the last picture is taken for the stack
7. The user has to move the carriage to the starting point. The carriage will move from this point back to the finish point. This point is where the stacking starts
8. The user has to start the stacking (GO!)

Once the parameters are set, the code automatically recalculates the necessary parameters. For example, if you change the f-number, the DOF and step size are automatically recalculated. If you change the starting point or finishing point, the travel distance and the number of steps are automatically recalculated.

After the stacking is initiated, the progress can be followed on the display. After a picture is taken, the progress is updated on the display. As the code proceeds further, more and more pictures will be taken and at the end, the number in the "progress" box will be equal to the number in the "number of steps" box.