50 encoder velocity calculation

CHANGELOG.rst

@@ -6,6 +6,16 @@ All versions in this changelog have two entries: ``driver`` and ``firmware``. Th
 have the same version, as communication protocol might change between versions. In the firmware/driver there
 is a safeguard to prevent miscommunication.
 
+Under development
+=================
+
+These are the features which are currently under development, but not yet released.
+
+* ``driver``:
+
+  * ``encoder``: calculation of average speed has been correctd (#50).
+
+
 Version 1.0.2
 =============
 

src/litexcnc/driver/modules/litexcnc_encoder.c

@@ -302,18 +302,17 @@ int litexcnc_encoder_process_read(void *module, uint8_t **data, int period) {
         // running average is not modified when an index-pulse is received, as this
         // means there is a large jump in position and thus to a large theoretical 
         // speed.
-        size_t velocity_pointer = 0;
         if (!(*(instance->hal.pin.index_pulse))) {
             // Replace the element in the array
-            instance->memo.velocity[velocity_pointer] = (*(instance->hal.pin.position) - position_old) * encoder->data.recip_dt;
+            instance->memo.velocity[encoder->memo.velocity_pointer] = (*(instance->hal.pin.position) - position_old) * encoder->data.recip_dt;
             // Sum the array and divide by the size of the array
             float average = 0.0;
             for (size_t j=0; j < LITEXCNC_ENCODER_POSITION_AVERAGE_SIZE; j++) {average += instance->memo.velocity[j];};
-            *(instance->hal.pin.velocity) = average * 0.125;
+            *(instance->hal.pin.velocity) = average * LITEXCNC_ENCODER_POSITION_AVERAGE_RECIP;
             *(instance->hal.pin.velocity_rpm) = *(instance->hal.pin.velocity) * 60.0;
             // Increase the pointer to the next element, revert to the beginning of
             // the array
-            if (velocity_pointer++ >= sizeof(instance->memo.velocity)) {velocity_pointer=0;};
+            if (encoder->memo.velocity_pointer++ >= LITEXCNC_ENCODER_POSITION_AVERAGE_SIZE) {encoder->memo.velocity_pointer=0;};
         }
     }
 

src/litexcnc/driver/modules/litexcnc_encoder.h

@@ -56,6 +56,7 @@
  * into account that at these low speeds the resolution of the speed is detoriated.
 */
 #define LITEXCNC_ENCODER_POSITION_AVERAGE_SIZE 8
+#define LITEXCNC_ENCODER_POSITION_AVERAGE_RECIP 0.125
 
 /** The ID of the component, only used when the component is used as stand-alone */
 int comp_id;
@@ -145,6 +146,7 @@ typedef struct {
     /** This struct holds data from previous cycles, so changes can be detected */
     struct {
         long period; /** period of a single cycle */
+        size_t velocity_pointer;
     } memo;
 } litexcnc_encoder_t;