diff --git a/firmware/controllers/core/fsio_impl.cpp b/firmware/controllers/core/fsio_impl.cpp
index 47bbb79f80..d8b8aac790 100644
--- a/firmware/controllers/core/fsio_impl.cpp
+++ b/firmware/controllers/core/fsio_impl.cpp
@@ -15,6 +15,10 @@
 #include "rpm_calculator.h"
 #include "efiGpio.h"
 
+/**
+ * in case of zero frequency pin is operating as simple on/off. '1' for ON and '0' for OFF
+ *
+ */
 #define NO_PWM 0
 
 fsio8_Map3D_f32t fsioTable1("fsio#1");
@@ -186,7 +190,7 @@ static void setFsioOutputPin(const char *indexStr, const char *pinName) {
 /**
  * index is between zero and LE_COMMAND_LENGTH-1
  */
-void setFsioExt(int index, brain_pin_e pin, const char * exp, int freq DECLARE_ENGINE_PARAMETER_SUFFIX) {
+void setFsioExt(int index, brain_pin_e pin, const char * exp, int pwmFrequency DECLARE_ENGINE_PARAMETER_SUFFIX) {
 	boardConfiguration->fsioPins[index] = pin;
 	int len = strlen(exp);
 	if (len >= LE_COMMAND_LENGTH) {
diff --git a/firmware/controllers/core/fsio_impl.h b/firmware/controllers/core/fsio_impl.h
index 484ad5ccbb..553f760bad 100644
--- a/firmware/controllers/core/fsio_impl.h
+++ b/firmware/controllers/core/fsio_impl.h
@@ -20,7 +20,7 @@ typedef Map3D<FSIO_TABLE_8, FSIO_TABLE_8, uint8_t> fsio8_Map3D_u8t;
 
 float getEngineValue(le_action_e action DECLARE_ENGINE_PARAMETER_SUFFIX);
 void setFsio(int index, brain_pin_e pin, const char * exp DECLARE_ENGINE_PARAMETER_SUFFIX);
-void setFsioExt(int index, brain_pin_e pin, const char * exp, int freq DECLARE_ENGINE_PARAMETER_SUFFIX);
+void setFsioExt(int index, brain_pin_e pin, const char * exp, int pwmFrequency DECLARE_ENGINE_PARAMETER_SUFFIX);
 
 void initFsioImpl(Logging *sharedLogger DECLARE_ENGINE_PARAMETER_SUFFIX);
 void runFsio(void);