Help need to implement IR communication b/w two microcntroller 89s52

I do not have any idea how to invert the bits..?

say2paul you can use "CPL" instruction in asm and in C you know the complement instruction



Arun

sorry I am newbie

Can you please explain with C example..!

think you would have to invert the bits before it gets to the rx pin,else with the start and stop bits of the frame inverted,the controller will not be able to make out the serial frame.

sashijoseph

Dear Sashi, Can you please explain it in detail. I do not have any idea how to invert the bits..?

say2paul

Hi Paul,
For an asynchronous transmission the data byte is sanwiched between a start bit and one or two stop bits.This constitutes a serial frame.
The start bit is always 0 and stop bit(s) are always 1.
Now,the tsop presents a low output when it receives a burst of ir ie with an input 1,it's output is 0.
Similarly when it's input is 0 ie no ir,it's output is high.

So when it receives the start bit it's output turns 1,instead of 0.This is read by the Rx pin which cannot decipher it as a start bit and hence the frame is not recognised.

Thus you are required to invert the output of the tsop before it reaces the Rx pin and not in software.
You could use a transistor inverter.