DHa4988

A simple, customizable driver for the a4988 stepper motor board for Arduino.

Example

const int enable = 2;
const int ms1 = 3;
const int ms2 = 4;
const int ms3 = 5;
const int step = 6;
const int dir = 7;

// initalize the stepper class
DHa4988 stepper(enable, dir, step, ms1, ms2, ms3);

void setup() {
  // change mode to Half step (0.9 degrees per step)
  stepper.setMode(HALF_STEP);
}

void loop() {
  // step 90 degrees
  stepper.step(90.0);
  delay(2000);
}

Functions

void setMode(uint8_t mode)

Specify the desired mode. Valid modes are:

Mode	Degrees per step	Default
FULL_STEP	1.8	YES
HALF_STEP	0.9	NO
QUARTER_STEP	0.45	NO
EIGHTH_STEP	0.225	NO
SIXTEENTH_STEP	0.1125	NO

---

void setDirection(uint8_t direction)

Set the desired direction. Valid directions are:

Direction	Default
CW	YES
CCW	NO

---

void setSpeed(uint8_t speed)

Set the desired speed. Speed is given in percentage of the maximum speed. Thus these values are between 0 and 100 inclusive. Max speed corresponds to 1667 steps per second. The table below shows how rpm varies with selected mode at maximum speed.

Mode	Degrees per second	RPM
FULL_STEP	3000	500
HALF_STEP	1500	250
QUARTER_STEP	750	125
EIGHTH_STEP	375	62.5
SIXTEENTH_STEP	187.5	31.25

Note speeds will most likely be slower due to the time it takes for digitalWrite

---

void step(float degrees)

Step the motor the specified amount of degrees.

The degrees must be a multiple of the current mode. ie. if The current mode is HALF_STEP, degrees must be a multiple of 0.9. If not, then the amount of steps will be rounded to the nearest integer. ie. If you want to step 2.0 degrees with HALF_STEP, it will only step 2 times for a total of 1.8 degrees. To step 2 degrees, you would could select EIGHTH_STEP which would step 9 times resulting in 2.025 degrees.

---

void enable()

Enable the motor for use if it was previously disabled. No need to call this otherwise as it is enabled by default.

---

void disable()

Disable the motor. This disables the outputs controlling the motor. The inputs and internal logic still remain operational so it is still possible to change the mode and direction of the motor.

---

void attachButton(uint8_t button, float degrees, uint8_t edge, uint8_t mode, bool autoDisable)

Attach a button such that upon its press and the specified edge and mode, the stepper will turn the specified degrees. Valid edges are D_RISING and D_FALLING which specify the rising or falling edge of the button. Valid modes are D_BUTTON_PULLUP and D_BUTTON_PULLDOWN which specify if a pullup or pulldown resistor are connected externally. Note that this function does not configure any internal pullup/down resistors. As with step(), the degrees must be a multiple of the current mode, or the button attach will be ignored. If autoDisable is set to true, then the motor will be disabled and automatically enable itself when a button press occurs. It will then disable itself until the next button press.

Example use:

// Our button is connected to digital pin 8
// We want to spin 180.0 on the rising edge of our button
// Based on the pulldown configuration the button will be LOW unless pressed
// The stepper will spin the instant the button is pressed as this is the rising edge
// Turn on auto disable
stepper.attachButton(D8, 180.0, D_RISING, D_BUTTON_PULLDOWN, true);

Note that this function has a 100ms delay for debouncing the button.

---

void checkButtonPress()

This function must be called in a loop in order to check for the conditions specified in attachButton(). attachButton() must be called before this function is ever called.

TODO

• Use pin interrupts if specified input allows it for selected board
• Configure internal pullup/down resistors if the selected board allows for it