Discussion in "8051 Discussion Forum" started by    Sharad chandra    Oct 27, 2007.
Sat Oct 27 2007, 02:25 AM
Respected Ajay Sir,

My self Sharad Chandra Sharma ,sir I have read the RC5 IR remote switch source code from 8051projects.net it is an excellent effort yet I m confused by two type problem both are inlisted below . Please try to solve it I will be very thankful to you.

I am unable to understand the concept that------How can microcontroller 8051 READ the received data( RC5 bits ) by using the software time delay.

In the software program of Phillips RC5 decoding (an 8-switch control asm code) , I have great confusion in “reading the IR bits along with the time delay” .I have explain my problem in details under problem 2.


Sir under the ‘main’ label after giving the 3.024ms a delay is given for AGC bits, after then the IR data is moved to carry bit (for reading the flip bit ) and further stored in FLIP location.

Under ‘fadd’ label the first 1.728ms delay is given then IR is moved to carry bit and further rotated into Accumulator , and DJNZ COUNT,fadd loop runs .

Sir my question is that way do you not given the delay for ‘FLIP bit or TOGGLE bit’ also under the ‘fcmd’ label initially 1.728ms delay is given and then command bit is readed way !
Or in other words we an say that
….moving the ‘flip bit’ into carry bit and further stored in FLIP location , DOSEN’T need time delay.

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Sat Oct 27 2007, 06:44 AM
Ok simple answers to your problems...
read the working of RC-5 Protocol here...

regarding your second problem whose answer lies in the above website itself.. You must understand that all the bits are spaced at 1.728mS away from each other.. and after the detection of first AGC bit.. i am giving delay till flip bit because we know that AGC bits are constant 1,1. So giving a delay of 3.024mS take straight to the center of Flip bit.
moving data from one location to other location need few microseconds. of course i have taken care of that...

I want you to please go through the documentation of IR in the link given above so that you can get a better picture. I am sure it will help you answer your doubts. If you still feel any problem.. feel free to ask me..

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