TPDD
Tandy Portable Disk Drive
There were two versions of the Tandy Portable Disk Drive, "26-3808 Tandy Portable Disk Drive" or "TPDD1", and "26-3814 Tandy Portable Disk Drive 2" or "TPDD2". Both were very similar. The original TPDD1 is a re-branded Brother FB-100.
Common features of both versions
- Size, shape, weight
- Batteris: 4 x AA
- Wall power: 5.5mm x 2.1mm, 6vdc, center negative, 400ma (Tandy 26-3804)
- Media: 3.5" DD, aka "720K" diskettes (not HD 1.44M)
- Drive is single-sided. The disks may be single or double-sided, but the drive only uses one side.
Documentation
Tandy Portable Disk Drive
100K
Tandy Portable Disk Drive 2
200K, in the form of 2 100K banks
3rd party extensions
Parts
Belt
Standard size code: FRW-8.5
Search "FRW 8.5 belt" on Google or ebay
Cable
The "RS-232C" interface to the TPDD is actually 5v TTL (0v to +5v), while RS-232 serial ports use -12v to +12v. So the cable isn't just a cable, it has electronics inside the DB25 plug to convert the signal levels between TTL and RS-232.
Pinout
+------------------------------------------------+ | | | | | RS-232C | | ___ | | +--+ +--+ +-----+ | | | 7 5 3 1 | | (o) | | | | 8 6 4 2 | | | | | +---------+ +-----+ | +------------------------------------------------+
- 1 GND
- 2 CTS
- 3 DTR
- 4 RTS
- 5 DSR
- 6 TXD
- 7 RXD
- 8 EB+ (External Battery +4.8 to +6v)
KiCAD source for schematic & pcb to build a cable
- Assembly:
- Solder all components to pcb per the render pics.
- Pull the two un-soldered pins from the top of the socket and discard.
- Cut the 9-pin plug off the serial cable. Strip the outer sheath back 1 to 2 inches. Strip each wire 1/8".
- Put 2 to 3 inches of 1/2" diameter heat shrink on the serial cable. (don't shrink yet)
- Identify which color wires go to which pins on the DB25 plug.
- Find pin 2 on the db25
- Find which color wire goes to pin 2 using a DMM continuity tester
- Repeat for all the numbered holes on the PCB: 2,3,4,5,6,7,20
- Cut any left-over wires short right at the cable sheath.
- Solder the wires to their matching numbered holes, with the wires on the top side (without the transistors).
- Put some hot-glue on the top side of the pcb in the "dog bone", press the end of the cable into the glue, and secure to the pcb with a zip-tie.
- Add some hot-glue around the soldered wires where they meet the pcb to immobilize them.
- Slide the heat-shrink up over the pcb and shrink.
Software
For "Model T"s
The normal way to use a TPDD is to install a TPDD_client on a "Model T" such as TRS-80 Model 100 or NEC PC-8201a.
Several such clients have been made. The drive came with a utility disk and a functional dos called "floppy" which supports only the TRS-80 Model 100, 102, or 200.
Others have been made by 3rd parties that provided more features or smaller ram footprint or more flexible installation/usage, and run on all the other Model T's from Kyotronic, NEC and Olivetti besides the Tandy models.
Various special purpose utility programs have been written by users as well.
For PCs
TPDD used standard double density 720k 3.5" disks, but used a format that is incompatible with modern pc drive controllers.
Normal MS-DOS formatted disks are written with MFM encoding, while the TPDD used FM encoding.
Even using special software to read non-standard formats, you can't make a normal drive & drive controller read or write FM.
To read or write a TPDD disk from a modern machine, you need a working TPDD drive and the special RS232-to-TTL level-shifting serial cable that came with it, and a "TPDD Client" software to talk to the drive over the serial connection the same way the M100 does.
There are several TPDD clients for more modern machines, although most of these are themselves also no longer modern.
For example Lap-Desk and PDD.exe are both 16-bit DOS programs that don't work on Windows. (But DO work in dosbox on linux/freebsd/osx)
One thing that is usable today is TpddTool.py, a TPDD Client utility written in Python.
Others
The TANDY WP-2 has support for using a TPDD built in to it's firmware.
There are TPDD Client apps for Cambridge Z88 to use a TPDD.
Related
There are also several TPDD_Emulators, which are programs that don't *use* a TPDD, but they emulate *being* a TPDD, so a Model 100, 102, 200, WP-2, NEC PC-8201, PC-8201a, PC-8300, Kyotronic KC-85, Olivetti M-10, Cambridge Z88, can save and retieve files on a modern computer using the TPDD protocol.
There are also a few hardware devices that emulate a TPDD.
One was called a NADSBOX, which is no longer available.
Another is a combination of 3 diy projects:
http://github.com/bkw777/PDDuino
http://github.com/bkw777/MounT
http://github.com/bkw777/BCR_Breakout