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Forum: µC & Digital Electronics AVR Assembler: Debugging IR Remote Control Transmitter


von Johannes F. (jofe)


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Hello,

I'm trying to develop a simple infrared remote-control transmitter, 
using an ATmega88A, assembler and the NEC modulation (please see 
https://www.mikrocontroller.net/articles/IRMP_-_english#NEC_+_extended_NEC 
for details on that).

My program isn't working correctly yet – after testing with a receiver 
failed, I connected a red LED to the output which produced the result 
that can be seen in the attached video: the LED blinks, but the 
transmission stretches out for circa one second, which is far too long – 
an NEC transmission should take about 60 ms.

I initially suspected wrong timer settings, but couldn't find any error. 
After reading through my code again and again, I decided to post it here 
in the hope that someone might have a look at it and maybe find the 
problem.

Thank you in advance for any help.

Best regards

– Johannes

von Lothar M. (Company: Titel) (lkmiller) (Moderator)


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Johannes F. wrote:
> I connected a red LED to the output which produced the result
A flashing LED is way too little to debug a serial interface. You should 
connect a oscilloscope instead. Because with that you can determine the 
real pulse times and check it against the mentioned 
https://www.mikrocontroller.net/articles/IRMP_-_english#NEC_+_extended_NEC 
and find out the factor your timing is wrong.

When its "fairly ecacxt" the factor 8 you shuld check the correct 
setting of the clkdiv8 fuse in your AVR.

: Edited by Moderator
von Johannes F. (jofe)


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Lothar M. wrote:
> You should connect a oscilloscope instead.

Yes, that's true of course, but unfortunately I don't have a DSO at the 
moment.

Lothar M. wrote:
> When its "fairly ecacxt" the factor 8 you shuld check the correct
> setting of the clkdiv8 fuse in your AVR.

I already checked that; it's not programmed (i.e. value 1).
I used the UART successfully with the same hardware directly before I 
flashed the current program, so the clock frequency has to be correct.

von S. L. (sldt)


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(Wilhelm M. - are you watching?)

Well now how about that?:
1
 ldi   temp0, 1<<WGM12  ; CTC mode
2
 xout  TCCR1A, temp0

WGM12 resides in TCCR1B.

von Johannes F. (jofe)


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S. L. wrote:
> WGM12 resides in TCCR1B.

Oh yes, that was a mistake – thank you!

I corrected that and, in addition, another error (forgot to clear the 
COM0A0 bit of TCCR0A in the ir_carrierOff macro, which caused the LED 
not to be switched off at the end of every other transmission).

Now, it works perfectly.

Again, S. L., thanks for your help!

Have a nice evening,
– Johannes

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