'I send literal 'FF' for 255'
Besides Octal, Hex is the next step up from just sending Binary! Not sure I really understand where the connection is missed? BCD - Binary Coded Decimal?
There are many excellent tutorials within the MDBT42Q web page:
Short of that I used our old friend Google with the 'site:' keyword qualifier:
Google: how to send an array of data over ble
and an example that was posted in the forum with corresponding source code:
re: 'without having to decode ASCII characeters (sic) in the iphone app'
Consider sending an encoded Json packet? Base64 encoding?
As a suggestion, post both sides of the communication as it exists now, so that we may better understand where the current thinking is.