update readme.md

AS5600.cpp

@@ -329,6 +329,7 @@ uint16_t AS5600::readAngle()
   if ((_directionPin == AS5600_SW_DIRECTION_PIN) &&
       (_direction == AS5600_COUNTERCLOCK_WISE))
   {
+    //  mask needed for value == 0.
     value = (4096 - value) & 0x0FFF;
   }
   _lastReadAngle = value;

README.md

@@ -467,6 +467,35 @@ int32_t getRevolutions();
 int32_t resetRevolutions();   //  replaces resetPosition();
 ```
 
+### Angular Speed + Cumulative position optimization.
+
+Since 0.6.4 it is possible to optimize the performance of getting both.
+- **getCumulativePosition()**
+- **getAngularSpeed()** 
+
+As both use to read the Angle, one can reuse this by setting the update flag to false.
+One must call **readAngle()** right before both of them
+In code:
+
+```cpp
+    ...
+    alpha = as5600.readAngle();
+    pos   = as5600.getCumulativePosition(false);
+    speed = as5600.getAngularSpeed(AS5600_MODE_DEGREES, false);
+
+    //  process the values...
+```
+
+Please note that the **mode** parameter for getAngularSpeed() becomes mandatory.
+
+The call to **readAngle()** caches the angle read and uses it in both functions.
+The savings are substantial, see **AS5600_position_speed.ino**
+
+The advantage is that both speed and pos are based upon the same reading.
+A disadvantage is that the latter of the two calls is not max up to date.
+
+Use with care.
+
 
 ### Status registers
 

examples/AS5600_position_speed/AS5600_position_speed.ino

@@ -37,25 +37,42 @@ void setup()
   Serial.print("Connect: ");
   Serial.println(b);
 
-  delay(1000);
-
-  start = micros();
-  as5600.getCumulativePosition();
-  as5600.getAngularSpeed();
-  stop = micros();
-  Serial.print("update true: \t");
-  Serial.println(stop - start);
-  delay(100);
-
-  start = micros();
-  as5600.readAngle();
-  as5600.getCumulativePosition(false);
-  as5600.getAngularSpeed(AS5600_MODE_DEGREES, false);
-  stop = micros();
-  Serial.print("update false: \t");
-  Serial.println(stop - start);
-  Serial.println();
-  delay(100);
+  for (uint32_t speed = 100000; speed <= 800000;  speed += 100000)
+  {
+    Wire.setClock(speed);
+    Serial.println(speed);
+    delay(100);
+
+    start = micros();
+    as5600.getCumulativePosition();
+    as5600.getAngularSpeed();
+    stop = micros();
+    Serial.print("update true: \t");
+    Serial.println(stop - start);
+    delay(100);
+
+    start = micros();
+    as5600.readAngle();
+    as5600.getCumulativePosition(false);
+    as5600.getAngularSpeed(AS5600_MODE_DEGREES, false);
+    stop = micros();
+    Serial.print("update false: \t");
+    Serial.println(stop - start);
+    Serial.println();
+    delay(100);
+  }
+
+  /*
+     about ~1% slower on AVR @100K
+    start = micros();
+    as5600.getCumulativePosition(true);
+    as5600.getAngularSpeed(AS5600_MODE_DEGREES, false);
+    stop = micros();
+    Serial.print("update false: \t");
+    Serial.println(stop - start);
+    Serial.println();
+    delay(100);
+  */
 
   delay(2000);
 }

examples/AS5600_position_speed/output_0.6.4_UNO.txt

@@ -0,0 +1,42 @@
+
+BOARD:  UNO
+IDE:    1.8.19
+SKETCH: AS5600_position_speed.ino
+
+
+AS5600_LIB_VERSION: 0.6.4
+64
+Connect: 1
+100000
+update true: 	1208
+update false: 	640
+
+200000
+update true: 	724
+update false: 	368
+
+300000
+update true: 	552
+update false: 	316
+
+400000
+update true: 	440
+update false: 	276
+
+500000
+update true: 	432
+update false: 	224
+
+600000
+update true: 	356
+update false: 	236
+
+700000
+update true: 	372
+update false: 	192
+
+800000
+update true: 	356
+update false: 	220
+
+followed by lots of data