Synth-DIY Yahoo! Groups Archives

Thread

Best way to read a signal?

2006-03-16 by filipesbp

Hi again,

My objective is to read a Infrared command signal (Airconditioner 
remote command), that is modulated in 38Khz, to later reproduze the 
commands, i've past the signal to TTL and the question is, what is the 
best way to read that signal?

I'm using ATMega128 and a crystal of 15.3Mhz to be 100% with USART.

External Interrupts?
Timer/Counter? 8bit? 16bit? Counter1? Counter2?
I will need to read at least at 76Khz (2x38Khz), right?
My first idea is to use a internal interrupt that occurs at a rate 
bigger 76Khz, and see if the signal is at 1 or 0, is this the best?

Re: [AVR-Chat] Best way to read a signal?

2006-03-16 by Dennis Clark

filipesbp wrote:
> Hi again,
> 
> My objective is to read a Infrared command signal (Airconditioner 
> remote command), that is modulated in 38Khz, to later reproduze the 
> commands, i've past the signal to TTL and the question is, what is the 
> best way to read that signal?
> 
> I'm using ATMega128 and a crystal of 15.3Mhz to be 100% with USART.
> 
> External Interrupts?
> Timer/Counter? 8bit? 16bit? Counter1? Counter2?
> I will need to read at least at 76Khz (2x38Khz), right?
> My first idea is to use a internal interrupt that occurs at a rate 
> bigger 76Khz, and see if the signal is at 1 or 0, is this the best?

Either an external interrupt or better yet, use an pulse/edge capture 
interrupt.

DLC
-- 
---------------------------------------
Dennis Clark    TTT Enterprises
---------------------------------------

Re: [AVR-Chat] Best way to read a signal?

2006-03-16 by kholt@sonic.net

Aren't you using the common 38Khz receiver that has a built-in
demodulator?  That will automatically produce the slow command
 data that can then be easily captured by the micro, by sampling or
edge interrupts.

Show quoted textHide quoted text

> Hi again,
>
> My objective is to read a Infrared command signal (Airconditioner
> remote command), that is modulated in 38Khz, to later reproduze the
> commands, i've past the signal to TTL and the question is, what is the
> best way to read that signal?
>
> I'm using ATMega128 and a crystal of 15.3Mhz to be 100% with USART.
>
> External Interrupts?
> Timer/Counter? 8bit? 16bit? Counter1? Counter2?
> I will need to read at least at 76Khz (2x38Khz), right?
> My first idea is to use a internal interrupt that occurs at a rate
> bigger 76Khz, and see if the signal is at 1 or 0, is this the best?
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>

Re: [AVR-Chat] Best way to read a signal?

2006-03-16 by Filipe Pereira

My first idea is not to use a receiver with built-in demodulator, because i don't now how to reproduce the modulation, and if is a larger modulation start bit or wherever (I'm saying this because i've tried to see a little of the signal in a "Communication Analyzer" and the start and stop bits is different of the middle.
I'm thinking in reproduce the signal already modulated, since is only 1 and 0, i think its easier, or not?

Show quoted textHide quoted text

Aren't you using the common 38Khz receiver that has a built-in
demodulator?  That will automatically produce the slow command
 data that can then be easily captured by the micro, by sampling or
edge interrupts.

Hi again,

My objective is to read a Infrared command signal (Airconditioner
remote command), that is modulated in 38Khz, to later reproduze the
commands, i've past the signal to TTL and the question is, what is the
best way to read that signal?

I'm using ATMega128 and a crystal of 15.3Mhz to be 100% with USART.

External Interrupts?
Timer/Counter? 8bit? 16bit? Counter1? Counter2?
I will need to read at least at 76Khz (2x38Khz), right?
My first idea is to use a internal interrupt that occurs at a rate
bigger 76Khz, and see if the signal is at 1 or 0, is this the best?







Yahoo! Groups Links




 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/AVR-Chat/

<*> To unsubscribe from this group, send an email to:
    AVR-Chat-unsubscribe@yahoogroups.com

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/

Re: [AVR-Chat] Best way to read a signal?

2006-03-16 by kholt@sonic.net

If you can find or figure out the bitstream for each command, then
you won't need to capture into the micro, but just program them
into EEProm.  You can usually find the bitstreams somewhere on-line
or from the manufacturer - at least this is true most TV remotes.
To observe and note the bistreams, attach your scope to the
demodulator output.  Set the transmitter and receiver at a moderate
distance apart, and keep ambient flourescent lighting to a minimum;
as you noted, the pulse widths do vary somewhat depending on
condtions.

Ken

Show quoted textHide quoted text

>              My first idea is not to use a receiver with built-in
> demodulator, because i don't now how to reproduce the
> modulation, and if is a larger modulation start bit or
> wherever (I'm saying this because i've tried to see a little
> of the signal in a "Communication Analyzer" and the start and
> stop bits is different of the middle.
>  I'm thinking in reproduce the signal already modulated, since is only 1
> and 0, i think its easier, or not?
>     Aren't you using the common 38Khz receiver that has a built-in
> demodulator?  That will automatically produce the slow command  data
> that can then be easily captured by the micro, by sampling or edge
> interrupts.             Hi again,  My objective is to read a Infrared
> command signal (Airconditioner remote command), that is modulated in
> 38Khz, to later reproduze the commands, i've past the signal to TTL
> and the question is, what is the best way to read that signal?  I'm
> using ATMega128 and a crystal of 15.3Mhz to be 100% with USART.
> External Interrupts? Timer/Counter? 8bit? 16bit? Counter1? Counter2? I
> will need to read at least at 76Khz (2x38Khz), right? My first idea is
> to use a internal interrupt that occurs at a rate bigger 76Khz, and
> see if the signal is at 1 or 0, is this the best?        Yahoo! Groups
> Links                        Yahoo! Groups Links   To visit your group
> on the web, go to:     http://groups.yahoo.com/group/AVR-Chat/   To
> unsubscribe from this group, send an email to:
> AVR-Chat-unsubscribe@yahoogroups.com   Your use of Yahoo! Groups is
> subject to:     http://docs.yahoo.com/info/terms/
>
>
>         SPONSORED LINKS
>    Atmel avr
> Microcontrollers                                       Intel
> microprocessors
>                  Pic microcontrollers
>          YAHOO! GROUPS LINKS
>      Visit your group "AVR-Chat" on the web.
>      To unsubscribe from this group, send an email to:
>  AVR-Chat-unsubscribe@yahoogroups.com
>      Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
>