Teensy 3.2 with Pololu DRV8825 and a stepper motor to perform rotary scans This program controls a NEMA 17 stepper motor using a Pololu DRV8825 motor driver. It Takes user input to define the boresight (zero) position and the start and stop angles in degrees relative to the zero position. Then it moves to the start position and waits for a HIGH level on SCAN_START_PIN. After this signal is received, the motor is stepped through to the stop position. At the stop position, the SCAN_COMPLETE_PIN is driven HIGH.
The Stepper motor is connected to a DRV8825 motor driver with one coil on A1/A2, and the other coil on B1/B2. It may turn out that one coil's leads have to be reversed to match the motor rotation direction with the program direction.
The NEMA 17 motor is assumed to execute 200 steps/revolution. Change the StepsPerRevolution constant for other values.
05/27/20: Performs an angular scan over user-supplied range of angles. By default a complete scan from start position to stop position is performed, followed by a return to the start position However, if the STEP_ENABLE_PIN (held HIGH by default) is pulled LOW, the program will wait until it goes HIGH before performing the next step. In this case, a scan iteration would go as follows
Step 1 - Scan parameters entered, motor moves to start position, waits for LOW on SCAN_START_PIN
Step 2 - Measurement program pulls SCAN_START_PIN LOW for 1 sec, then back HIGH
Step 3 - Measurement program takes a measurement & retrieves step# & angle value via I2C request
Step 4 - Measurement program pulls SCAN_STEP_ENABLE_PIN LOW
Step 5 - Motor moves to first/next step, and outputs HIGH on SCAN_STEP_COMPLETE_PIN
Step 6 - Measurement program waits for HIGH on SCAN_STEP_COMPLETE_PIN
Step 7 - Measurement program takes a measurement & retrieves step# & angle value via I2C request
Step 8 - Repeat Steps 4-7 until scan complete
Step 9 - SCAN_COMPLETE_PIN goes HIGH
07 June 2020: Revised the program to allow user to (R)repeat the current scan, start a (N)new one, or (Q)quit the program