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 Post subject: Infrared TI - Need Help
PostPosted: Wed 27 Jan, 2010 5:04 pm 
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Hi, i am trying to make the infrared module of ben ryves, but i have a problem, my calculator recept the signal but don't emmite anything .. Have i make a mistake when i have choose my IR led ? i haven't find any SFH484 or SFH485 so i have take this one :

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=267-8425&x=34&y=12



and i have a (stupid) question, why must we use asm80 ? why the calculator can't recieve and send with linkGet() and linkSend() in TI basic ?


Sorry for my english, i'm french .. if you have questions or if you haven't understand something, tell me.


Thanks for your answer ! And great job ben ryves !


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PostPosted: Wed 27 Jan, 2010 7:45 pm 
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Welcome to MaxCoderz!

The HIR8811 appears to be similar enough to an SFH484/485 to work.

If you look at the IR LED using a digital camera, does it flicker when the software claims to be sending something (substituting a regular LED in its place should show the same if you don't have access to a digital camera).

Not all IR signals work with the software, unfortunately. If you have access to a Sony device, I recommend trying the Sony-specific software as an experiment.

The TI uses a specific protocol to exchange data using its link port. This protocol is not suitable for directly transmitting over IR, though a microcontroller can be used to act as an adaptor (e.g. IR Link). IR signals can be generated in software using a simple IR LED and demodulator, but the software has to do all of the work and be specially designed with this in mind.


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PostPosted: Wed 27 Jan, 2010 9:07 pm 
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Thank you very much for your express response :!:

For my test i have use my PS2 telecommand and i have use your software, and i arrive to create layout, it receive the signal and it recognise it, but i have a problem to send.

I have film with my camera but it does not flicker, and i have try with a normal led and it does not work too. I have verify the polarity of the led on my circuit.


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PostPosted: Wed 27 Jan, 2010 10:13 pm 
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Which calculator model are you using? I wonder if different models have slightly different I/O port hardware (I use an old black TI-83+). The I/O lines on the link port are open-collector, so will float when deactivated and can be held to 0V by writing a 1 to the port; I'm surprised that you can't seem to get anything out of yours. The ports themselves seem to be pretty resilient; I used a home-made serial cable for years with mine that output 10V into the port (whoops) and people plug headphones/speakers directly into the ports for sound programs without problems. I assume you can still send/receive programs to the calculator, implying that the port still works?

If you directly connect the LED between the link port lines (the cathode to the outside/shield and the anode to the ring) with no other hardware the program might still work, just with a much shorter range (you may need to stand right up close to the thing you're trying to control). You could use the camera/LED test as before.

If it still doesn't work, and you have some way of building a buffer between the calculator and the LED (e.g. a 555 Schmitt trigger) you could try that; a pull-up resistor (say 10K) between the input to the 555 and +5V may be required, and the output of the 555 is inverted so the LED should be connected between this output and 0V via a 330R resistor or similar.


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