Step 2

Part 1 - Understanding

All new devices by pioneer electronics are connected by a bus-system. This is becaue you kneed only one system remote and one remote-receiver in order to control a complete hifi-deck. For example, the amplifier receives a signal for the tape-deck and gives it on the bus. The tape deck listens on that bus and executes the remote command.

The bus is realized in a very simple way: all devices are connected to each other by a two-wire-cable, one is for the SR, the other for digital audio. The ground is taken from audio-ground. All devices are connected parallel to the bus, which is risen to 5V by an active SR-Receiver (such as an amplifier). For sending information, the sending unit pulls it down to 0V several times. The duration of the downtimes contains the coded information.

If you want to send data, you just have to connect the bus to ground. You can get the bus from the SR-out of the last device, or you can take it on the sr-input of your receiver.

The protocol is explained very quickly:

• The sending device pulls down the bus for 9ms, lets it raise for 4ms, for initializing the transfer.
• The next thing is an 8-bit-package, called the device-id. A zero is represented by 0,7ms lo, followed by 0.35ms hi, a one is represented by 0,7ms lo, followed by 1,4ms hi. The device-id tells, which device should listen to the following command. A list of the most important devices is given in the table below, a detailed list is in the source code.
• Next 8-bit-package is the first byte negotiated, for error detection.
• The third byte is the command which is to be executed, e.g. play, stop or pause or whatever. Again, the most important are in the table below, complete list in source.
• Now, as the second byte, the third one negotiated.
• Commands may be repeated at 10 Hz maximum, for example, if you want to step 15 tracks up, or want to pull the volume up.

A list of device-ids:

A1	Tape
A2	CD-Player
A4	Tuner
A5	Amplifier
A8	Laserdisc-Player
AB	Video-Recorder

The most important commands:

17	Play
18	Pause
16	Stop
10	Forward
11	Backward
1C	Power

Part 2 - The Hardware

As written above, you just need a piece of hardware, which connects the bus to ground. If you wand to control devices, which are not connected to an active sr-receiver, you can pull up the bus to 5V. If your PC-ground is not connected to the ground of your hifi-equipment, eg. via a soundcard, you will have to connect the masses. On the other hand, you should NOT connect them twice, if you have a something like a soundcard. Otherwise, you would create a mass-loop which would result in a 50Hz-line-noise.

For controlling such a device i reccomend the parallel port, because it is easy to control, and because it operates on the same voltage levels.

For the "short-circuit" we take a transistor, emmiter to ground, collector to the bus, base over resistors to DB0 and Ground. You could take a BC546. If thats not available, take anything else wich can switch about 200mA and has a working point about 5V.

You get the following schematic:

Fig.1:The schematic

SR is the inner pole of the connector. Pay attention that you DO NOT use the outer one as ground. It is for digital data transmission, if you need a grounding, take it from a cinch-connector.

If you do not know the pins of the parallel port, here are the important ones:

Pin	Signal
2	D0
3	D1
18-25	GND

As you can see, I misuse DB1 for raising the bus. If this results in errors, change the program to hold DB1 on 0.

If you didn't understand a single word of the above, but you can't continue your live without having such a cool control, send me a mail. I can solder a complete interface for you, for the price of the hardware, and perhaps a beer or two ;)

Part 3 - The Software

Now for the software. This one is not easy, because you need exact timing of down to 0,35ms. The dos-software uses loops, it makes n additions, and hopes, that the cpu needs the same time for each one. This results in a few consequences:

1. Yu have to tune n for each and every computer you want the tool to run on.
2. In multitasking environments as windows or dr, you can't even expect that the PC behaves the same all of the time, you will have to adjust n every time anonther progarm is launched in background.

The linux software comes without such problems: if you have enabled "enhanced rtc-support" in your kernel, you can have timing up to a resolution of 1/8000 sec. But even Linux is not realtime-enabled, so you may have to fine-tune some vars. Further more, you need to have root-privileges for setting the RTC to such a high resolution.

The software is available in different versions:

• Source code for a Turbo Pascal unit (Usendsr.pas)
• A ready-compiled Dos-Tool with nice menu (pioct-dos.zip)
• A package for linux (pioct.tgz)

The Linux-Doku is the best, so download the linux-package even when you wand to use the dos-package.

And now: have fun soldering, and sorry very much for my bad "inglisch".