Add a new function for linear motion scenes

[XingYunFei580]

For the linear reciprocating motion of the lead screw nut driven by the motor, according to the expected linear displacement (s) and the known screw lead (d), we can add a public function "goback(double s, int d)" in the head file to achieve the goal more simply and intuitively. Of course, other necessary data, such as the motor speed and pulse number, have been completed through other settings.
in the file "BasicStepperDriver.h", add:
class BasicStepperDriver {

Public

void goback(double s, int d);
long calcStepsForGoBack(double s, int d) {
return s/d * motor_steps * microsteps;
}
};

in the file"BasicStepperDriver.cpp"，add：

void BasicStepperDriver::goback(double s, int d){
move(calcStepsForGoBack(s,d));
}

An example program as below:

#define MOTOR_STEPS 300
#define RPM 200
#define DIR_PIN 7
#define STEP_PIN 8
#define SLEEP 9
#define MICROSTEPS 1
BasicStepperDriver stepper(MOTOR_STEPS, DIR_PIN, STEP_PIN, SLEEP)

int d=5; //screw lead 5mm
double s=30.4; //nut moving distance 30.4mm

void setup( ) {
stepper.begin(RPM, MICROSTEPS);
}

void loop( ){

stepper.goback(s, d);
delay(100);
stepper.goback(-s, d);
delay(100);
}

[laurb9]

Thanks for the suggestion. Linear motion I find is a subset of geared drives, where the move amount is multiplied by some factor. I had been considering adding the geared motor functionality separate from the rest but I am still unconvinced just to avoid a multiplication with move().