feat: add linear hall position sensor driver

src/encoders/linearhall/LinearHall.cpp

@@ -0,0 +1,55 @@
+#include "LinearHall.h"
+
+LinearHall::LinearHall(int _hallA, int _hallB, int _centerA, int _centerB, int _pp){
+  pinA = _hallA;
+  pinB = _hallB;
+  centerA = _centerA;
+  centerB = _centerB;
+  pp = _pp;
+}
+
+float LinearHall::getSensorAngle() {
+  float rawA = analogRead(pinA);
+  float rawB = analogRead(pinB);
+
+  //offset readings using center values, then compute angle
+  float a = rawA - centerA;
+  float b = rawB - centerB;
+  float reading = atan2f(a, b);
+
+  //handle rollover logic between each electrical revolution of the motor
+  if (reading > prev_reading) {
+    if (reading - prev_reading >= PI) {
+      if (electrical_rev - 1 < 0) {
+        electrical_rev = pp - 1;
+      } else {
+        electrical_rev = electrical_rev - 1;
+      }
+    }
+  } else if (reading < prev_reading) {
+    if (prev_reading - reading >= PI) {
+      if (electrical_rev + 1 >= pp) {
+        electrical_rev = 0;
+      } else {
+        electrical_rev = electrical_rev + 1;
+      }
+    }
+  }
+
+  //convert result from electrical angle and electrical revolution count to shaft angle in radians
+  float result = (reading + PI) / _2PI;
+  result = _2PI * (result + electrical_rev) / pp;
+
+  //update previous reading for rollover handling
+  prev_reading = reading;
+  return result;
+}
+
+void LinearHall::init () {
+  pinMode(pinA, INPUT);
+  pinMode(pinB, INPUT);
+
+  //establish initial reading for rollover handling
+  electrical_rev = 0;
+  prev_reading = atan2f(analogRead(pinA) - centerA, analogRead(pinB) - centerB);
+}

src/encoders/linearhall/LinearHall.h

@@ -0,0 +1,31 @@
+#ifndef LINEAR_HALL_SENSOR_LIB_H
+#define LINEAR_HALL_SENSOR_LIB_H
+
+#include <SimpleFOC.h>
+
+class LinearHall: public Sensor{
+  public:
+    LinearHall(int hallA, int hallB, int centerA, int centerB, int pp);
+
+    // initialize the sensor hardware
+    void init();
+
+    // Get current shaft angle from the sensor hardware, and 
+    // return it as a float in radians, in the range 0 to 2PI.
+    //  - This method is pure virtual and must be implemented in subclasses.
+    //    Calling this method directly does not update the base-class internal fields.
+    //    Use update() when calling from outside code.
+    float getSensorAngle() override;
+
+  private:
+    int pinA;
+    int pinB;
+    int pp;
+    int electrical_rev;
+    float prev_reading;
+
+    int centerA;
+    int centerB;
+};
+
+#endif