created separate function for hex to char

Dependencies:   SDFileSystem ds3231 eeprom_Nikita mbed testUniGraphic_150217

Fork of SS_SensePOC2P0_11Dec2017_USERPID by rashmi v

Revision:
0:c47fb0c1bbf6
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Tue Dec 27 10:30:48 2016 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/9baf128c2fab
\ No newline at end of file