Apple Trackball
| ADB trackballs | |
|---|---|
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|
| Kensington Turbo Mouse ADB, a third-party trackball | |
| Manufacturer | Apple (built into portables); Kensington and other third parties (external) |
| Type | Pointing device (trackball) |
| Interface | Apple Desktop Bus |
| Compatible | ADB-equipped Macintosh computers |
An ADB trackball is a trackball that works as the pointing device on the Apple Desktop Bus. Apple's own trackballs were built into its portable computers. The Macintosh Portable has one in place of a mouse, and the PowerBook 140 and 170 have a 30 mm trackball centred below the keyboard.[1][2] External ADB trackballs for desktop Macintosh computers came from third parties, such as Kensington's Turbo Mouse ADB (pictured). To the Macintosh, any trackball on the bus is the pointing device, the same as a mouse.[3]
The Macintosh Portable trackball
[edit | edit source]Apple describes the Macintosh Portable's low-power trackball as working "something like an upside-down mouse". It is electrically compatible with ADB but uses a few pins of a large shared connector in place of the 4-pin mini-DIN. That connector is mechanically the same as the keyboard's, so the trackball can be installed on either side of the machine.[1]
| Pin | Signal | Function |
|---|---|---|
| 1 | GND3 | Chassis ground |
| 2–26 | n.c. | Not connected |
| 27 | GND2 | ADB signal ground |
| 28 | +5 V | 5-volt power supply |
| 29 | ADB.DATA | Bidirectional serial data |
| 30–33 | n.c. | Not connected |
| 34 | GND | Ground |
Only pins 1, 27, 28, 29 and 34 are connected.[1]
The trackball's default device handler ID is $0001 and its address is the same as a mouse's. Moving the top of the ball to the right moves the cursor right, and moving it downwards moves the cursor down. It has one button, which works as the mouse button. The Power Manager IC removes power from the trackball when the computer sleeps and restores it on wake, and the trackball is designed to be working within 80 ms of power being applied.[1]
Apple warns that every input device on the Macintosh Portable's ADB must be a low-power version. Keyboards and mouse devices from other Macintosh models are not usable on it, and connecting them "could cause an unacceptable decrease in the +5 volt supply voltage and result in improper operation".[1] That applies equally to a desktop ADB trackball.
ADB rules that apply to any trackball
[edit | edit source]Apple's ADB specification binds third-party trackballs as it does Apple's own devices:[4]
- The default address for relative-position devices, mouse or trackball, is $03.
- In Apple's standard mouse, register 0 holds the button state in bit 15 (0 = pressed), Y movement in bits 14-8 and X movement in bits 6-0, with bit 7 always 1.
- A device must answer a Talk command within 260 µs. When the bus is idle the transceiver repeats the last Talk command every 11 ms.
- All devices on the bus together may draw no more than 500 mA from the +5 V supply.
- Cables should be no longer than 5 m, with capacitance no more than 100 pF per metre, and Apple does not recommend daisy-chaining more than three devices on one port.
- Do not unplug and reattach an ADB device while the computer is running.
Multi-button and programmable trackballs use a different device handler ID and the maker's own driver software. Some of that software asks the user for the ADB ID numbers of the keyboard and pointing device; on every Macintosh they are 2 and 3.[3]
Maintenance and faults
[edit | edit source]The mechanism of an opto-mechanical trackball is the mouse mechanism turned over. In Apple's mouse a rubber-coated steel ball turns two capstans, each connected to a slotted interrupter wheel, one for X and one for Y, and the mouse reports square-wave signals as the wheels turn.[4] Cleaning follows the same pattern as for a mouse; see Apple Desktop Bus Mouse.
If a trackball is not recognised:
- Connect it alone, with nothing else on the bus.
- Check +5 V between pins 3 and 4 of the computer's ADB port, and that pin 1 (ADB data) idles high through the 470 Ω pull-up on the logic board.[4]
- Add up the load on the bus against the 500 mA limit.[4]
- Check the cable for continuity on all four conductors while flexing it at the strain relief.
On a Macintosh Portable, a trackball that is dead for a moment after the machine wakes is within Apple's design; one that stays dead is not.[1]
See also
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Apple Computer, Guide to the Macintosh Family Hardware, second edition, Addison-Wesley, 1990, Chapter 8 "Apple Desktop Bus", pp. 303-304, "Macintosh Portable low-power trackball" and Table 8-5. Hosted as File:Apple Guide to the Macintosh Family Hardware 2nd Edition 1990.pdf.
- ↑ Apple Computer, Macintosh PowerBook 140 and Macintosh PowerBook 170 Developer Note, 1991, Chapter 1 "The Hardware", p. 3: "built-in 3.0-mm travel keyboard with centered pointing device (30-mm trackball)". Hosted as File:Macintosh PowerBook 140 and 170 Developer Note 1991.pdf.
- ↑ 3.0 3.1 Apple Computer, Tech Info Library article 17771, "Macintosh Apple Desktop Bus Device ID Numbers", 17 May 1995: the primary pointing device, "whether it is a mouse, a trackball, or a trackpad", is ADB device 3. Hosted in File:Apple Tech Info Library ADB keyboard and mouse articles.pdf, PDF p. 21.
- ↑ 4.0 4.1 4.2 4.3 Guide to the Macintosh Family Hardware, 2nd ed., Chapter 8: p. 290 (do not unplug and reattach a device while the computer is running), p. 291 (Table 8-1, connector pinout and 470 Ω pull-up), p. 295 (500 mA total, 5 m cable, 100 pF per metre, no more than three devices per port), p. 300 (mouse mechanism), p. 301 (Table 8-4, register 0 of the Apple Standard Mouse), pp. 314-316 (11 ms repeat of the last Talk command; 260 µs response), pp. 322-324 (Table 8-16 default addresses, $03 for relative devices; Table 8-17 reserved device handler IDs). Hosted as File:Apple Guide to the Macintosh Family Hardware 2nd Edition 1990.pdf.