diff --git a/ACS712.cpp b/ACS712.cpp
index fb8dba7..1273a60 100644
--- a/ACS712.cpp
+++ b/ACS712.cpp
@@ -180,7 +180,10 @@ float ACS712::mA_DC(uint16_t cycles)
       value = (value + _analogRead(_pin))/2;
     }
     //  for RTOS
-    if (i % 2 == 1) yield();
+    if ((i & 0x0001) == 0x0001)  //  every 2nd iteration
+    {
+      yield();
+    }
     sum += (value - _midPoint);
   }
   float mA = sum * _mAPerStep;
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9f16961..43597ac 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,8 +7,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
 ## [0.3.9] - 2024-01-11
-- add yield() in multiple reads to better support RTOS
-- update readme.md (empty compatibility table)
+- add yield() to improve the behaviour under RTOS
+- update readme.md (add compatibility table).
 - minor edits
 
 
diff --git a/README.md b/README.md
index ffc3d8a..03f1bf3 100644
--- a/README.md
+++ b/README.md
@@ -174,7 +174,7 @@ This function is intended for signals with unknown Form Factor.
 - **float mA_DC(uint16_t samples = 1)** blocks < 1 ms (Arduino UNO) as it calls **analogRead()** twice.
 A negative value indicates the current flows in the opposite direction.
   - 0.2.8 the parameter samples allow to average over a number of samples.
-  - 0.3.9 calls yield() every 3 analogRead's to support RTOS (a bit).
+  - 0.3.9 calls yield() every 2nd iteration to improve behaviour under RTOS.
 
 
 #### mA_AC_sampling performance trick.