CC2640 Configure EXT CLK in ccfg.c

Hi

What you have to do is :

#define SET_CCFG_MODE_CONF_SCLK_LF_OPTION            0x1          // External LF clock

and then set this one to the corresponding DIO number

#define SET_CCFG_EXT_LF_CLK_DIO                         0x01                        // DIO number if using external LF clock

and if your CLK frequency is different than 32.768kHz, then you have to compensate this by setting this field 

#define SET_CCFG_EXT_LF_CLK_RTC_INCREMENT               0x800000   // RTC increment representing the external LF clock frequency

You can find all the information you need here:

C:/ti/tirtos_simplelink_2_13_00_06/products/cc26xxware_2_21_01_15600/doc/register_descriptions/CPU_MMAP/CCFG.html#EXT_LF_CLK

However, instead of directly modifying ccfg.c, it's recommended to copy the whole ccfg.c into ccfg_appBLE.c and modify from there.(this is stated in the ccfg_appBLE.c)