--- a/main/Kconfig.projbuild	Sat Nov 23 19:10:05 2019 +0100
+++ b/main/Kconfig.projbuild	Sat Nov 23 21:43:14 2019 +0100
@@ -33,11 +33,12 @@
             help
                 Port number for I2C Master device.
 
-        config I2C_MASTER_FREQUENCY
-            int "Master Frequency"
-            default 100000
-            help
-                I2C Speed of Master device.
+	config I2C_MASTER_FREQUENCY
+           int "Master Frequency"
+	   range 100000 400000
+           default 100000
+           help
+               I2C Speed of Master device in Hz.
 
     endmenu