diff --git a/STM32F1/variants/STM32VLD/board/board.h b/STM32F1/variants/STM32VLD/board/board.h
index ba8d556..be2f19e 100644
--- a/STM32F1/variants/STM32VLD/board/board.h
+++ b/STM32F1/variants/STM32VLD/board/board.h
@@ -38,7 +38,8 @@
 
 
 
-#define CYCLES_PER_MICROSECOND    24
+//#define CYCLES_PER_MICROSECOND    24
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 //#define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 #define SYSTICK_RELOAD_VAL      23999  /* takes a cycle to reload */
 
diff --git a/STM32F1/variants/generic_gd32f103c/board/board.h b/STM32F1/variants/generic_gd32f103c/board/board.h
index 209bc36..50dd989 100644
--- a/STM32F1/variants/generic_gd32f103c/board/board.h
+++ b/STM32F1/variants/generic_gd32f103c/board/board.h
@@ -36,7 +36,7 @@
 #ifndef _BOARD_GENERIC_STM32F103C_H_
 #define _BOARD_GENERIC_STM32F103C_H_
 
-#define CYCLES_PER_MICROSECOND    72
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 #define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 
 #define BOARD_NR_USARTS           3
diff --git a/STM32F1/variants/generic_stm32f103c/board/board.h b/STM32F1/variants/generic_stm32f103c/board/board.h
index 97231e0..09351a6 100644
--- a/STM32F1/variants/generic_stm32f103c/board/board.h
+++ b/STM32F1/variants/generic_stm32f103c/board/board.h
@@ -36,7 +36,7 @@
 #ifndef _BOARD_GENERIC_STM32F103C_H_
 #define _BOARD_GENERIC_STM32F103C_H_
 
-#define CYCLES_PER_MICROSECOND    72
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 #define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 
 #define BOARD_NR_USARTS           3
diff --git a/STM32F1/variants/generic_stm32f103r8/board/board.h b/STM32F1/variants/generic_stm32f103r8/board/board.h
index 5f6855d..c274d64 100644
--- a/STM32F1/variants/generic_stm32f103r8/board/board.h
+++ b/STM32F1/variants/generic_stm32f103r8/board/board.h
@@ -36,7 +36,7 @@
 #ifndef _BOARD_GENERIC_STM32F103R8_H_
 #define _BOARD_GENERIC_STM32F103R8_H_
 
-#define CYCLES_PER_MICROSECOND    72
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 #define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 
 #define BOARD_NR_USARTS           3
diff --git a/STM32F1/variants/generic_stm32f103t/board/board.h b/STM32F1/variants/generic_stm32f103t/board/board.h
index 5454958..9b261f6 100644
--- a/STM32F1/variants/generic_stm32f103t/board/board.h
+++ b/STM32F1/variants/generic_stm32f103t/board/board.h
@@ -36,7 +36,7 @@
 #ifndef _BOARD_GENERIC_STM32F103T_H_
 #define _BOARD_GENERIC_STM32F103T_H_
 
-#define CYCLES_PER_MICROSECOND    72
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 #define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 
 #define BOARD_NR_USARTS           2
diff --git a/STM32F1/variants/generic_stm32f103v/board/board.h b/STM32F1/variants/generic_stm32f103v/board/board.h
index 210dbf8..92f2bf8 100644
--- a/STM32F1/variants/generic_stm32f103v/board/board.h
+++ b/STM32F1/variants/generic_stm32f103v/board/board.h
@@ -38,7 +38,7 @@
 /* A few of these values will seem strange given that it's a
  * high-density board. */
 
-#define CYCLES_PER_MICROSECOND  72
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 #define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 
 #define BOARD_BUTTON_PIN        PC0
diff --git a/STM32F1/variants/hytiny_stm32f103t/board/board.h b/STM32F1/variants/hytiny_stm32f103t/board/board.h
index 194b2e5..179e5e5 100644
--- a/STM32F1/variants/hytiny_stm32f103t/board/board.h
+++ b/STM32F1/variants/hytiny_stm32f103t/board/board.h
@@ -36,7 +36,7 @@
 #ifndef _BOARD_GENERIC_STM32F103C_H_
 #define _BOARD_GENERIC_STM32F103C_H_
 
-#define CYCLES_PER_MICROSECOND    72
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 #define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 
 #define BOARD_NR_USARTS           2
diff --git a/STM32F1/variants/maple/board/board.h b/STM32F1/variants/maple/board/board.h
index caebcc7..5a09286 100644
--- a/STM32F1/variants/maple/board/board.h
+++ b/STM32F1/variants/maple/board/board.h
@@ -34,7 +34,7 @@
 #define _BOARD_MAPLE_H_
 
 /* 72 MHz -> 72 cycles per microsecond. */
-#define CYCLES_PER_MICROSECOND  72
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 
 /* Roger clark
 
diff --git a/STM32F1/variants/maple_mini/board/board.h b/STM32F1/variants/maple_mini/board/board.h
index 10bcb5a..9064807 100644
--- a/STM32F1/variants/maple_mini/board/board.h
+++ b/STM32F1/variants/maple_mini/board/board.h
@@ -36,7 +36,7 @@
 #ifndef _BOARD_MAPLE_MINI_H_
 #define _BOARD_MAPLE_MINI_H_
 
-#define CYCLES_PER_MICROSECOND    72
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 #define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 
 #define BOARD_NR_USARTS           3
diff --git a/STM32F1/variants/microduino/board/board.h b/STM32F1/variants/microduino/board/board.h
index 2a1295f..0c06363 100644
--- a/STM32F1/variants/microduino/board/board.h
+++ b/STM32F1/variants/microduino/board/board.h
@@ -37,7 +37,7 @@
 #ifndef _BOARD_MICRODUINO_STM32_H_
 #define _BOARD_MICRODUINO_STM32_H_
 
-#define CYCLES_PER_MICROSECOND    72
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 #define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 
 /* Roger Clark. 
diff --git a/STM32F1/variants/nucleo_f103rb/board/board.h b/STM32F1/variants/nucleo_f103rb/board/board.h
index 02f46d9..b27862d 100644
--- a/STM32F1/variants/nucleo_f103rb/board/board.h
+++ b/STM32F1/variants/nucleo_f103rb/board/board.h
@@ -33,7 +33,7 @@
 #ifndef _BOARD_MAPLE_H_
 #define _BOARD_MAPLE_H_
 #define _BOARD_NUCLEOF103RB_ 1 // hack for HardwareSerial.cpp for a new order of serials
-#define CYCLES_PER_MICROSECOND  72
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
 #define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 
 /* Roger clark. Removed defines for LED pin and Button pin as they are not Arduino API defines */
diff --git a/STM32F3/variants/discovery_f3/board/board.h b/STM32F3/variants/discovery_f3/board/board.h
index 179dede..6b04a8b 100644
--- a/STM32F3/variants/discovery_f3/board/board.h
+++ b/STM32F3/variants/discovery_f3/board/board.h
@@ -38,8 +38,8 @@
 
 #include <libmaple/stm32.h>
 
-#define CYCLES_PER_MICROSECOND    72
-#define SYSTICK_RELOAD_VAL     71999 /* takes a cycle to reload */
+#define CYCLES_PER_MICROSECOND	(F_CPU / 1000000U)
+#define SYSTICK_RELOAD_VAL     (F_CPU/1000) - 1 /* takes a cycle to reload */
 
 enum {
 		PC13, PC14, PC15,