MSX REMOTE CONTROL

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By NYYRIKKI

Enlighted (5595)

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31-10-2015, 17:13

I got yet another strange idea: Plug the IR led to your sound output and use SCC or MoonSound to create the carrier. Easy? Hell no, but it just might be doable. I didn't do all the math though.

By NYYRIKKI

Enlighted (5595)

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31-10-2015, 18:43

enribar: I did the math for SCC and it seems to backup my idea. Remember that there is also this "Deformation register" in #98E0 where you can set a frequency multiplier. You probably need to aim to about 38KHz. The analog filtering of sound signal may anyway affect the end result as 38KHz is about double that you can hear. How ever at least in theory you should be then able to send the commands to your DVD player simply by beating up/down the volume register. TIP: You can usually see the IR light, if you point your digital camera / phone camera to the led.

By ricbit

Champion (438)

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31-10-2015, 21:09

What about drawing a pattern on the screen and plugging the led on the video output? There's no audio frequency limiting there.

By enribar

Paragon (1073)

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01-11-2015, 01:28

So... thankyou for your suggestions :-)
I don't know anything about remote controlling with LED, IR, formats, differences between new and old DVDs, etc.
So I ask: are DVD players remote controlled by sound or by infrared?
Are 38KHz sounds like infrared?
Instead of SCC, can I achieve those frequence with the tape REC output cable connected to a speaker?

By NYYRIKKI

Enlighted (5595)

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01-11-2015, 05:14

ricbit wrote:

What about drawing a pattern on the screen and plugging the led on the video output? There's no audio frequency limiting there.

I have not investigated using of video output at all, but I think the fact that you can't alter left/right border of the MSX screen makes this already impossible. I also think that if enribar wants to do something like laserdisk game, then he needs the video output for other purposes.

enribar wrote:

I don't know anything about remote controlling with LED, IR, formats, differences between new and old DVDs, etc.
So I ask: are DVD players remote controlled by sound or by infrared?
Are 38KHz sounds like infrared?

No, usually DVD players are controlled trough infrared. Infrared led operates at about 320GHz frequency range, but you don't need to worry about that as it is enough to power the led to get the IR light on. The communication it self is pretty close to what is used on MSX to store data to cassette player although carrier frequency is much higher (typically 35-40KHz) and data rate is typically much lower (only few bytes / second)

There are dozens of manufacturers of DVD players and they have dozens of models, so there is no universal solution to your problem. How ever most of them work with 38KHz carrier wave.

Quote:

Instead of SCC, can I achieve those frequence with the tape REC output cable connected to a speaker?

I did not calculate anything, but I think that getting out something like 38KHz is possible with OTIR or OUTI, but my head hurts even when I'm thinking about modulating that.

If I would be you, I would start with following plan:

- I would buy a kit something like this
- I would connect the LED to sound output (maybe with some small resistor in series to protect the led & output)
- I would try to play a sound and see if I can see a light with a camera
- I would connect the receiver to joystick port (+5v=pin 5, GND=pin 9, data ie. trigger1=pin 6)
- I would initialize SCC wavetable with square wave
- I would try to get the SCC to play a correct carrier frequency and monitor if I get reaction on joystick trigger

If I could get everything working until this point, I would write a routine that:

- Samples data from joystick trigger, converts it to volume and writes it to write buffer
- takes data from read buffer and writes it to SCC volume address
- Makes a little delay
- Repeats enough many times.
(This way the actual sampling rate is not important as both recording & playing is done at same speed)

Then I would disable SCC page from memory, press a key from remote and run the program. Then I would enable SCC page again, swap the write buffer and read buffer addresses and see if the DVD player reacts for running the program.

As you can see there are very many IF-words in this plan and it is pretty general, so I can't tell that this is the correct way to proceed, but it was a general idea that I was thingking of.

By enribar

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01-11-2015, 14:47

Great and creative idea! But very difficult (for me) to realize.
I though it was more simple, for example, as first step connect the msx to the keyboard of a universal dvd RC.
Prices of new URC are quite low in internet.
Another idea: a cartridge with IR and FPGA reprogrammable with new codes, with the aim to handle more and more dvd models.
This also is theory, I cannot realize it and where to start, maybe asking in some electronic fan forums?
There are also Apps that allow to control TVs with smartphones,

By NYYRIKKI

Enlighted (5595)

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01-11-2015, 16:21

I miserably fail to understand, how you consider building address decoding logic, 8255 or other kind of PPIs, URC + endless amount of jump wires + other needed stuff as more easy solution than connecting 5 wires + writing pretty straight forward code from a plan... For me the designing of FPGA chip with similar MSX interface + maybe some sort of CPU + program to handle the tasks + memory to store the codes, programming the chip and connecting it to MSX sounds even more ridiculous. Sure, if your skills are that heavily on the FPGA hardware design, then go ahead, but I'm afraid that you are going to waste a lot of time fighting with your design. To be honest I can't think of any more complex ways of doing such a simple basic task.

Please even consider something ready made... Like ie. ATTINY-85... You don't have to design the microcontroller, you can make it MIRC compatible and if you like, there are ready made IR protocol libraries that you just have to select from. You only need to design some minimal transfer protocol to upload your remote codes. On the good side the whole design will be so small that it can be mounted inside MSX joystick connector and you don't need to spend days or weeks on building, designing, simulating and debugging.

By sp4

Master (214)

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03-11-2015, 00:21

enribar wrote:

So... thankyou for your suggestions :-)
I don't know anything about remote controlling with LED, IR, formats, differences between new and old DVDs, etc.
So I ask: are DVD players remote controlled by sound or by infrared?
Are 38KHz sounds like infrared?
Instead of SCC, can I achieve those frequence with the tape REC output cable connected to a speaker?

No Enribar, 38KHz sound it's noto like an infrared: infrared are a different kind of thing than a ultrasounds.
I hope of to has been clear. Doesn't it?
The infrared is a kind of light and the ultrasound in a kind of sound over 20KHz of frequency.

By RetroTechie

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03-11-2015, 14:32

Funny (or too bad) how this thread got hijacked.. Radio-controlled robots are way cooler than TV/DVD remotes, mucho kudoz there, usuario_msx2! Cool

But on the topic of IR remotes,

NYYRIKKI wrote:

Please even consider something ready made... Like ie. ATTINY-85... You don't have to design the microcontroller, you can make it MIRC compatible and if you like, there are ready made IR protocol libraries that you just have to select from. You only need to design some minimal transfer protocol to upload your remote codes.

That's already over-engineering it. All you need is an IR-led, capacitor, transistor, and a few resistors. An IR receiving IC (that integrates IR sensor, amplifier and filter) at the cost of a few peanuts, if you want to receive or analyse protocols as well (typical example). Wired up directly to joystick connector or (equally suited for those MSX'es that have it) the printer port.

MSX'es Z80 can generate required signals (or decode what's incoming) fine by itself. No need for Arduino or similar in between, that's just making things more complex/difficult to program than necessary.

IR communication is much like serial / MIDI / tape storage etc, Z80 code snippets to do it measure in a few dozen or (at most) hundreds of bytes. IIRC, most DVD/TV remotes use a carrier frequency of ~36 KHz (like still popular RC-5 protocol). There's a few different carrier frequencies, but many many different protocols and no common standard for the meaning of transmitted codes. So any IR software that supports various brands will have a # of 'drivers' for each brand/protocol/model. But like said, most drivers can be very small.

So controlling your DVD or TV using your MSX is quite simple. The fun is more in analysing protocols. That is: say your TV/remote uses a protocol that has 6 bits for a command (= 64 commands), but sends only 20 of those. What do the other 44 codes do? Or IR communication between 2 MSX'es...

By NYYRIKKI

Enlighted (5595)

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04-11-2015, 02:28

@usuario_msx2 Indeed your robot is very cool, sorry for hijacking, but I hope all remote controlling fits under the subject.

@RetroTechie I think you forgot the oscillator although you can build that with few transistors as well, but maybe easier is to use 555 or similar... Anyway what you describe is pretty much what MIRC is... I think it is a bit matter of taste, if you want to write few lines of code and use 1x micro controller or if you want to do the same with components. If you want to be able to adjust the carrier or something like that, then maybe micro controller approach is better... On most of the cases it is not very important if the carrier is +- few kHz off. It mostly affects the distance the led needs to be from receiver.

How ever with MIRC type of solution the software needed is pretty much same as I described with SCC... Just forget the init and replace "volume" with trigger 2 or so. -> You still need to write the looping part of the program.

@enribar Can you describe what is the "very difficult" part? Maybe we can find a way around that.

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