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Topic: Using IR Toy for 455khz (Read 5148 times) previous topic - next topic

Using IR Toy for 455khz

Good day all,

I am definitely not an expert in IR electronics, so I have a few questions I hope someone could answer for me. The thing is that I would like to purchase an “USB Infrared Toy v2” as I would like to be able to control my computer with a Bang & Olufsen Beo4 remote control. As you may know, Bang & Olufsen uses 455 khz for their system and the Infrared Toy is designed for 38 khz. My question is therefore:

- Can I installed an additional infrared demodulator (receiver) designed for 455 khz in the IRRX-socket in the “breakout area” of the PCB?
- Do I need to change the firmware of the IC for doing this?

Further, as I also would like to send IR signals from the computer to the TV and other stuff on both 38 khz and 455 khz, I have the following question:

- Can you send all frequencies with the installed IR transmitter?
- Can I install an additional IR transmitter in the IRTX-socket in the “breakout” area on the PCB?
- Does above two things require any changes in the firmware of the IC?

I hope someone would spend a few minutes helping me out here. Any help is highly appreciated!

Re: Using IR Toy for 455khz

Reply #1
here is a related question, for our friend the search engine.. and Ian =P
-  The break out is pointed to the side, can an additional IRRX with optional receive frequency piggy back the original?

Quote
- Do I need to change the firmware of the IC for doing this?
Yes you would need firmware changes, and maybe some hardware hacking as well. I'm unsure of the interplay between the two demodulators, but I think they can share the bus if they are both active low and reject the off frequency signals as they should. The 455k might be handled by the raw ir mode? However the sampling rates are around 10kHz in the fastest current modes.

I've been using the toy firmware for some baseline code, so i know abit about it's timers.
In the HardwareProfile.h
T1_OFFSET and H,L ... TMR1 = 65430 = 0xFF96 ~= 113.2kHz, this is the equivilent ~4times sampling speed of 10kHz
T2_RXsampleperiod() TC2CON = 0, PR2 = 106 gives 113.2kHz
t2_rxsampleperiod is the timer for SUMP mode. Your hacking might start here.

Quote
- Can you send all frequencies with the installed IR transmitter?
- Can I install an additional IR transmitter in the IRTX-socket in the “breakout” area on the PCB?
- Does above two things require any changes in the firmware of the IC?

[s:]The TX times are dictated by the hardware, the transmit transistor ...[/s:] http://www.fairchildsemi.com/ds/BC/BC818.pdf
T1 is rated for 100MHz.
R5 Disconnects T1, isolating the IRTX if needed.
I'm sorry I have no insight to the transmit timers for you, it likely uses timer1 detailed above.

Re: Using IR Toy for 455khz

Reply #2
Quote
- Can I installed an additional infrared demodulator (receiver) designed for 455 khz in the IRRX-socket in the “breakout area” of the PCB?
- Do I need to change the firmware of the IC for doing this?

You will need a 455khz demodulator for sure. You could tap into the IRRX and attach a second demodulator, watch the pinout because it is not designed for that. You may be better off removing the old demodulator, though I have never tried it, electrically it won't hurt anything to have two (they are open collector outputs).

I'm not sure about the firmware. Short answer - probably not. Longer answer - if the protocol isn't anything fancy, the existing firmware should be able to measure it. If the encoded signal is too short/fast, the timers might not be able to keep up. You can encode more data on a 455khz carrier than a 38khz carrier. Currently we measure in 23.333us increments.

Quote
Further, as I also would like to send IR signals from the computer to the TV and other stuff on both 38 khz and 455 khz, I have the following question:

- Can you send all frequencies with the installed IR transmitter?
- Can I install an additional IR transmitter in the IRTX-socket in the “breakout” area on the PCB?
- Does above two things require any changes in the firmware of the IC?

The transmitter is moduled by a hardware PWM that can do a range of frequencies. Check this page to see how to calculate the settings for 455khz, these can be sent to the IR TOy by applications on the PC:
http://dangerousprototypes.com/docs/USB ... .280x06.29
http://dangerousprototypes.com/docs/Raw ... _frequency

The IRTX is the raw PWM out, it doesn't ahve enough power for a transmitter. You'd need to add a transmitting circuit like the one used with the existing IR LED.

We currently transmit in 23.33uS chunks. As long as the signal isn't too fast for the timer, it probably needs no changes.
Got a question? Please ask in the forum for the fastest answers.

Re: Using IR Toy for 455khz

Reply #3
Hey Guys,

Thank you very much for the swift reply. I will look into this, study and most likely revert with further questions. :)


Cheers,

Jeppe

Re: Using IR Toy for 455khz

Reply #4
Hi Jeppe

Did you have any luck with the 455khz and remote control with beo4?

Re: Using IR Toy for 455khz

Reply #5
It should work fine if you have a 455 receiver. Even though the frequency is crazy high, the pulse/space lengths are pretty similar to that of normal remotes.