Reduced interrupt blocking time

Changed interrupt-based sensors to only copy volatile variables during interrupt-blocking sections, and do computations with them after re-enabling interrupts.

Author: dekutree64

src/sensors/Encoder.cpp

@@ -101,12 +101,14 @@ void Encoder::handleIndex() {
 
 // Sensor update function. Safely copy volatile interrupt variables into Sensor base class state variables.
 void Encoder::update() {
+  // Copy volatile variables in minimal-duration blocking section to ensure no interrupts are missed
   noInterrupts();
-  // TODO: numerical precision issue here if the pulse_counter overflows the angle will be lost
-  full_rotations = pulse_counter / (int)cpr;
-  angle_prev = _2PI * ((pulse_counter) % ((int)cpr)) / ((float)cpr);
   angle_prev_ts = pulse_timestamp;
+  long copy_pulse_counter = pulse_counter;
   interrupts();
+  // TODO: numerical precision issue here if the pulse_counter overflows the angle will be lost
+  full_rotations = copy_pulse_counter / (int)cpr;
+  angle_prev = _2PI * ((copy_pulse_counter) % ((int)cpr)) / ((float)cpr);
 }
 
 /*
@@ -123,8 +125,11 @@ float Encoder::getSensorAngle(){
   function using mixed time and frequency measurement technique
 */
 float Encoder::getVelocity(){
-  // Make sure no interrupts modify the state variables in the middle of these calculations
+  // Copy volatile variables in minimal-duration blocking section to ensure no interrupts are missed
   noInterrupts();
+  long copy_pulse_counter = pulse_counter;
+  long copy_pulse_timestamp = pulse_timestamp;
+  interrupts();
   // timestamp
   long timestamp_us = _micros();
   // sampling time calculation
@@ -133,8 +138,8 @@ float Encoder::getVelocity(){
   if(Ts <= 0 || Ts > 0.5f) Ts = 1e-3f;
 
   // time from last impulse
-  float Th = (timestamp_us - pulse_timestamp) * 1e-6f;
-  long dN = pulse_counter - prev_pulse_counter;
+  float Th = (timestamp_us - copy_pulse_timestamp) * 1e-6f;
+  long dN = copy_pulse_counter - prev_pulse_counter;
 
   // Pulse per second calculation (Eq.3.)
   // dN - impulses received
@@ -155,9 +160,7 @@ float Encoder::getVelocity(){
   prev_timestamp_us = timestamp_us;
   // save velocity calculation variables
   prev_Th = Th;
-  prev_pulse_counter = pulse_counter;
-  // Re-enable interrupts (ideally this would restore to the previous state rather than unconditionally enabling)
-  interrupts();
+  prev_pulse_counter = copy_pulse_counter;
   return velocity;
 }
 

src/sensors/HallSensor.cpp

@@ -96,11 +96,14 @@ void HallSensor::attachSectorCallback(void (*_onSectorChange)(int sector)) {
 
 // Sensor update function. Safely copy volatile interrupt variables into Sensor base class state variables.
 void HallSensor::update() {
+  // Copy volatile variables in minimal-duration blocking section to ensure no interrupts are missed
   noInterrupts();
-  angle_prev = ((float)((electric_rotations * 6 + electric_sector) % cpr) / (float)cpr) * _2PI ;
-  full_rotations = (int32_t)((electric_rotations * 6 + electric_sector) / cpr);
   angle_prev_ts = pulse_timestamp;
+  long last_electric_rotations = electric_rotations;
+  int8_t last_electric_sector = electric_sector;
   interrupts();
+  angle_prev = ((float)((last_electric_rotations * 6 + last_electric_sector) % cpr) / (float)cpr) * _2PI ;
+  full_rotations = (int32_t)((last_electric_rotations * 6 + last_electric_sector) / cpr);
 }
 
 
@@ -119,14 +122,16 @@ float HallSensor::getSensorAngle() {
 */
 float HallSensor::getVelocity(){
   noInterrupts();
-  float vel = 0;
-  if (pulse_diff != 0 && ((long)(_micros() - pulse_timestamp) < pulse_diff*2) ) // last velocity isn't accurate if too old
-    vel = direction * (_2PI / (float)cpr) / (pulse_diff / 1000000.0f);
+  long last_pulse_timestamp = pulse_timestamp;
+  long last_pulse_diff = pulse_diff;
   interrupts();
-  return vel;
-}
-
+  if (last_pulse_diff == 0 || ((long)(_micros() - last_pulse_timestamp) > last_pulse_diff*2) ) { // last velocity isn't accurate if too old
+    return 0;
+  } else {
+    return direction * (_2PI / (float)cpr) / (last_pulse_diff / 1000000.0f);
+  }
 
+}
 
 // HallSensor initialisation of the hardware pins 
 // and calculation variables