|Remote Control for This Board|
NEC Infrared Protocol
16 bits for the address (address + inverse) require 27ms to transmit time .and the 16 bits for the command (command + inverse) also require 27ms to transmit time.
because (address + address inverse) or (command+command inverse) will always contain 8 ‘0’s and 8 ‘1’s so (8 * 1.125ms) + (8 * 2.25ms) == 27 ms .
according to this total time required to transmit the frame is (9ms +4.5ms +27ms+27ms) = 67.5 ms.
Extended NEC protocol (not used in this demonstration)
If the key on the remote controller is kept depressed, a repeat code will be issued, typically around 40ms after the pulse burst that signified the end of the message. A repeat code will continue to be sent out at 108ms intervals, until the key is finally released. The repeat code consists of the following, in order:
A 9ms leading pulse burst
A 2.25ms space
A 562.5µs pulse burst to mark the end of the space (and hence end of the transmitted repeat code).
the figures give blow show the timing of repeat codes
if user keeps the key depressed the repeat codes keep coming
Decoding NEC Protocol with microcontroller
Decoding NEC is really easy ,there are certainly various methods to do, some examples i have see n used polling method in which the firmware keep polling the input pin of microcontroller which connects to IR sensor , other method is to user interrupt ,in this demonstration we will be using the interrupt method as this one is better, we will be using interrupt on change.