TPDD

Overview

There were two versions of the Tandy Portable Disk Drive. Both were very similar. The drive is a 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.

Tandy Portable Disk Drive

100K

TPDD bootstrap procedure

TPDD Operation Manual

Command Reference

Software Manual

Tandy Portable Disk Drive 2

200K in the form of 2 100K banks (still only uses one side of the disk)

TPDD-2 bootstrap procedure

TPDD-2 Operation Manual

Parts

Belt

Standard size code: FRW-8.5

Search "FRW 8.5 belt" on Google or ebay

Cable

M100SIG/Lib-09-PERIFERALS/TPDD.DO

Pinouts

+------------------------------------------------+
|                                                |
|                                                |
|                 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 NC

Rick Shear has taken a new and very careful look at a real cable, and the Marty Goodman doc, and has probably identified the "msyery" components that Marty Goodman talks about. This is probably the most electrically accurate cable.

https://rsmicro.wordpress.com/2018/08/26/tpdd-cable/

https://rsmicro.wordpress.com/2018/09/08/built-tpdd-cable-comparison-to-oem/

https://oshpark.com/shared_projects/vntX40yC

https://www.digikey.com/short/pm9h87

Pictures of my own cables built usibg Rick's pcb

• It is quite a pain in the neck crimping the tiny individual dupont connector pins. You will also need a pin crimper that fits AWG28 wires/pins like a good old Radio Shack 276-1595, or generic "SN-28B" sold by several different manufacurers, just pick any. They can be less than $15 on ebay

• The numbers 1 to 8 on the silk-screen on the pcb DO correspond to the numbers on the TPDD connector in the diagram above and the Marty Goodman doc. So that is how you can tell which pin on the pcb is supposed to go to which position on the dupont connector. Just match up the numbers from the pcb silkscreen with the positions in the diagram above. One of the pictures in the google photos album above also shows both connectors side by side with all wires connected and all colors and all positions visible, so you can also use that picture to just look at the colors of the wires on both sides.

Software

For PCs

TPDD used double density 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. Most of these are themselves also no longer modern. For example Lap-Desk and PDD are both 16-bit DOS programs that don't work on Windows.

TpddTool Python TPDD Client

For M100/102/200

The normal way to use a TPDD is to install a "dos" on an M100. Several such dos's have been made. The drive came with a utility disk and a functional dos called "floppy". Others have been made by 3rd parties that provided more features or smaller ram footprint or more flexible installation/usage. There are also various special purpose utility programs aside from dos's.