Unilink

The Sony Unilink System

A technical overview
presented as a one-act play in a not-quite-Shakespearian Style (21st century translation provided at the end)

Dramatis Personae:
Metrulio, a musician
Antius, a tradesman

scene: a carriagehouse

Antius is present at opening, attending to small labours in the
carriagehouse

Enter Metrulio carrying a parcel under his arm

Metrulio: Well met, Antius! How are thee to this fine morrow?

Antius: In quite good humour, my friend. What doth thou tarry with in thine arms?

Metrulio: Thou art a keen observer. Come and behold this exceedingly excellent system I have purchased for my carriage yet this very day.

Antius: A new Head Unit, do I declare, Metrulio!

Metrulio: Aye, aye.

Antius: And how canst though afford it, thy scurvy dog? Art thou not still in debt unto me for 30 ducats from out visit to the tavern a week prior? Dost thou shill me?

Metrulio: Nay, nay, in truth I do not, for I am good for it all. I did hence purchase this for a very pittance of a sum for t'was an open box clearance item -- I would be less than a man should I have not leapt on this opportunity as though a tiger on prey.

Antius: Not so much a tiger a a wee thrice-bred feline.

Metrulio: Curb thy noisome verbiage and join thee in my regalia! This shall compliment us both, for I shall be freed from the bondage of using a Cassette Tape Adapter to get my music from my Mp3 Player outword twixt mine speakers!

Antius: Though dost expect me to believe, nay accept, that you didst afford a Stereo with Auxiliary in on a meager income such as yours?

Metrulio: No credit is given to mine actions, little brother? Cease thy pander and view these, and then salt thine hat and eat it.

Metrulio unpacks the head unit and shows the rear side to Antius.

Metrulio: Art thou the town jester, or canst though see these two dulcet darlings labeled so elegantly as "Bus In Left" and "Bus In Right"; Never was such poetry issued from the lips of man nor machine..

Metrulio swans about in a euphoric state for a moment.

Antius: Metrulio.

Metrulio: ...

Antius: Metrulio, I say, Metrulio.

Metrulio halts abruptly.

Metrulio: I am present, you strumpet. Speak thy mind or shut thy beak.

Antius: Art thou a fool?

Metrulio: Art thou a fiddlers elbow?

Antius: I say, art thou a fool, you great pillock?

Metrulio: I should say not, yet I will still cause thee great pain for it!

Antius: Thou art still a fool, and a penniless fool hence.

Metrulio: Is there a point to thy ends here, or dost thou simply delight in the hearing of thine own words?

Antius: Fucketh thee.

Metrulio: I shall run thee through, knave!

Metrulio draws his sword half from scabboard in a menacing fashion.

Antius: Let thine hand thy manhood leave be, and I shall explain why though art a torpid potatoe.

Metrulio: I shall run thee through! See if I don't!

Antius: Give calm to thyself, lest thy do shat theeself.

Metrulio looks flusted.

Antius: didst thou actually think in thy infantile mind that thou wouldst pur'chase a fly stereo with Auxiliary inputs for thy meager wage? Nay, this is a Sony so surely though hast be much deceived.

Metrulio: Strewth! How now?

Antius: Bring thine eyes hither.

Antius takes head unit, points to a spot on the rear for Metrulio to
see.

Antius: This is a Sony Unilink port and is the key to thine eventual woes, like a storm on the horizon.

Metrulio: I see not how. Pray, what is a Unlink port, friend?

Antius: The port itself is a simple 8 pin DIN connector that is found on many Sony stereo systems, amplifiers and other electronics. It is a multidrop serial bus used for controlling devices and retrieving data from them. It is used to daisychain multiple devices together simultaneously -- thou can have up to 7 CD changers in one bus!

Metrulio: So 'tis a remote control system, eh?

Antius: Moreso then that; not only does it control, it also returns data and polls devices on the bus.

Antius moves closer to Metrulio.

Antius: You see, unless a device is connected to the Unlink bus, the Aux In lines in the head unit will not accept input; So without a special XA-300 Auxiliary Activator, though art mightily screw'ed.

Metrulio: Nay! I am not as thick as a stunted Frenchmen! I can simply built a pigtail and jumper the sense lines on the connector! I am still victorious!

Antius: Aye, ye may think that, and thee would be correct is this weren't a Sony deck.

Metrulio: Indulge me?

Antius: Not without a stiff drink and a blindfold.

Metrulio: Nay, thou clodpoll! Indulge me as to why mine brilliant scheme won't work.

Antius: Ah. Well, the head unit does not detect devices based on a close circuit and sense pins. Instead, the devices on the bus must announce themselves using the S-Link protocol.

Metrulio: The devices on the bus must be intelligent! That's.. That's..

Antius and Metrulio: (Together) EVIL!

Metrulio: Wait. This protocol as you say cannot be to complex, canst it?

Antius: Nay, S-link is not too demented. Not half as thee.

Metrulio: So, could one not talk to Wozniak the Geek and get him to build a mystical device to emulate a Unilink device?

Antius: Jumping ahead of me thou are. There is the 'Gnunlink' project with has code and schematics for making an Auxiliary input activator using a PIC microcontroller -- All thou'est needs is a few rudimentary parts, a PIC chip with 8 I/O lines and a PIC programmerer.

Metrulio: I mayest still come out on top.

Antius: For once.

Antius looks pensive.

Antius: But if thou canst hack together a box, thou cast still putchase an XA-300 Auxiliary adapter from Sony for $100, or the Slink-e third-party activator for $250.

Metrulio: The non-Sony is more expensive?

Antius: Aye; like the Gnunilink device, it not only activates the aux inputs, but also allows signals to be sent to and intercepted from the head unit allowing your Mp3 title to be displayed on the LCD of the deck in they carriage.

Metrulio: Most excellent. Tell me more about the connector itself.

Antius: As I said before, it is an 8-pin DIN style connector, though only 7 pins are used; they are Reset, SIRCS (for remote control host commands), Clock (for signal timing, about 8mHz), Data, Bus On, Constant +12v for memory and the necessary common ground wire.

Metrulio: The plug itself looks like private knowledge? How doest I obtain a unilink plug to use in the Gnunilink project?

Antius: Though can either talk to a Sony representative and get one directly from them, or the easier way is to get a Unilink extension cable and use the male end of it to built your box.

Metrulio: I am not fucked. Huzzah.

Antius: Huzzah. Though doest still owe me 30 ducats, though.

Metrulio: Gaze upon my extended middle finger.

Metrulio gives Antius the finger.

Metrulio exunt.

Fin.

In English.

Unilink is a stereo peripheral connection system developed by Sony and used in some car audio systems (and to a lesser extent home systems) from Sony, Kenwood, Denon and a few others.

Physically it is a round DIN style connector with 8 pins (with 7 pins actually used), looking a lot like an ADB connector. One end of a cable is plugged into the Unilink port on the "Host" unit (i.e. stereo), and the other end is plugged into another device. That device will usually have another downstream port to plug into another device so you can have up to 7 devices all controlled from the Host. This can be 7 CD Changers, MD Players, VCRs or any combination of anything that has a Unilink interface.

The audio itself is handled via a separate audio connection usually called "Bus Left/Right" which sends the audio signals from the devices on the chain to the upstream back to the head unit, this means that any head unit that has a Unilink port will have Bus Audio In ports in the form of two RCA connectors.

One would assume that because it has audio in connectors, it can just accept audio right out of the box; this is not so. The audio inputs themselves are not activated unless there is something plugged into the Unilink port on the unit; And don't think you can just make a pigtail jumper to make it think there is something, either -- it won't turn on those ports unless it's a valid Unilink device.

This is because Unilink devices use the S-Bus protocol to communicate with each other; when the stuff is turned on the head unit polls all the devices on the chain and only accepts audio if if it gets a valid response in the protocol it understands.

There are ways around this; the first is to use a Sony XA-700 Auxiliary Activator; it is a Unilink device with two RCA inputs and nothing else. You plug it in to the Unilink bus, then plug your device into it and then you can input audio from any source; the downside it it retails for $99 USD.

Two non-Sony options are the Slink-e for $250 and a Gnunilink device for the cost of parts. The Slink-e is an Aux activator that also talks to the bus in a way that you can make text show up on the Head units display using serial data from a computer. The Gnunilink system is a set of code and schematics to make your own Activator using a PIC chip and some Free code, but requires PIC programming hardware and a Unilink connector (which you can get by buying a Unilink extention cable and cutting off the end you want).

The connector itself is an 8-pin (7 used) deal. Their functions are not too complex: Reset, SIRCS (S-Link Interface Remote Control System, for remote control host commands), Clock (for signal timing, about 8mHz, not the time of day), Data, Bus On, Constant +12v for memory preservation and a common ground.