How to build a DriveWire serial cable

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Home / Hardware - How to build a DriveWire serial cable

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General cable information

When connecting a CoCo to a DriveWire 3 or 4 server you will need a particular serial cable. Here are two ways to build such a cable. USB to serial adapters generally work well.

Note : The physical cable connecting the CoCo to the Server is recommended to be no longer than 10 feet in length..

Possible cable combinations

Single, direct USB-A male RS232 cable converter to 4-Pin DIN male cable

Parts :

• FTDU USB-A male RS232 serial adapter (example)
• Solderable male 4-pin DIN plug (example)

To connect this the FTDI cable wires yellow, orange, and black are used :

• Yellow is connected to the DIN pin 4
• Orange is connected to DIN pin 2
• Black is connected to DIN pin 3

This has been tested and worked in GNU/Linux and Windows to 115,200 kbps.

DB-9 or DB-25 female (PC side) to 4-Pin DIN male (CoCo side) cable

Parts :

• DB-9 or DB-25 male connector
• Solderable 4 pin DIN plug (example)
• 4 conductor cable

At a minimum, the serial line shall carry the following four wires:

• Ground
• Vcc
• RD (Receive Data)
• TD (Transmit Data)

A 4 pin male DIN connector shall be on one end of the cable which will mate to the jack on the back of the CoCo marked “Serial I/O”. The other end of the cable shall be either a DB-9 or DB-25 female connector which will mate to an appropriate serial port on the Server.

The following table shows the connections between the CoCo 4 pin male DIN connector to either a 9-pin DB-9 female serial connector or a 25-pin DB-25 female serial connector :

CoCo DIN connector	DB-9	DB-25
Pin 1 (CD)	Pin 3 (TX)	Pin 2 (TX)
Pin 2 (RX)	Pin 3 (TX)	Pin 2 (TX)
Pin 3 (GND)	Pin 5 (GND)	Pin 7 (GND)
Pin 4 (TX)	Pin 2 (RX)	Pin 3 (RX)

Coco DIN connector	Legend
	CD - status line RS-232C IN - serial data input GND - ground, zero voltage reference RS-232C OUT - serial data output

This cable may be built based upon the following diagram :

Optional USB-A male to RS-232 DB9 female serial adapter for modern computers

Note : If you don't have access to an older PC with a serial port with a male DB9 connector, you will need an additional serial converter :

• USB male to DB-9 female RS232 female serial adapter (example adapter)

Such converters range in price from about $10 - $20 (or less from chinese providers, with longer shipping times) and can be purchased from most electronics stores and online. If they don't have it on the shelf, ask someone and they can most likely order it for you. You will still need the cable above as this is just an adapter to be able to connect it to PC's with no DB-9 male serial port.

Alternatively, you can also still purchase an add-on PCI or PCIx serial card. TigerDirect and NewEgg still stock a large selection of these cards. The internal serial cards tend to offer better data transfer rates than the USB to Serial adapters in testing.

Source

• Scott Adams (direct FTDI to 4-Pin DIN cable)
• Tandy Service Manual - Color Computer 3 NTSC/Pal Version - p. 47-48
• Drivewire physical interface requirements - from the [DriveWire Specification https://sourceforge.net/p/drivewireserver/wiki/DriveWire_Specification] (DB9 to 4PN-DIN male)