error: 'feedback_instruction' was not declared in this scope

Arduino: 1.6.8 (Windows 10), Board: "Arduino/Genuino Uno"

E:\FSM_0412_USART\FSM_0412_USART.ino: In function 'void loop()':

FSM_0412_USART:217: error: 'feedback_instruction' was not declared in this scope

feedback_instruction(inst_in); // copy the sensors instructions into instruction_in array so that they can be treated by the FSM

^

exit status 1
'feedback_instruction' was not declared in this scope

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

That looks like an error all right. Now how did you reach that error ... is please post your code by copying it, then pasting the code between 'code tags'. You probably have not created a function called 'feedback_instruction' correctly.

Instructions.

Please, you must show us your complete sketch. Attach your code using the </> icon on the left side of the posting menu.
Put your sketch between the code tags:
[code] Your code goes here. [/code]

.