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How to build a DriveWire serial cable

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Revision as of 23:56, 4 March 2021 by MagicFab (talk | contribs) (Added info from SourceForge cable specs, 4PIN DIN pinout from RS CoCo 3 service manual)
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Home / Hardware - How to build a DriveWire serial cable


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..

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

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

A 4 pin 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 DIN connector to either a 9-pin DB-9 serial connector or a 25-pin DB-25 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

  1. CD - status line
  2. RS-232C IN - serial data input
  3. GND - ground, zero voltage reference
  4. RS-232C OUT - serial data output

Direct USB male RS232 cable converter to 4-Pin DIN male cable

Parts :

  • FTDU USB male RS232 serial adapter (example)
  • Solderable 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 kpbs.

USB male to RS-232 DB9 female serial adapter, DB9 male to 4-Pin DIN male cable

Parts :

  • USB male to DB-9 RS232 male serial adapter (example adapter) - needed for modern PCs which most probably don't have a DB9 serial port
  • DB9 male connector
  • Solderable 4-pin DIN plug (example)
  • 4 conductor cable

This cable may be built based upon the following diagram :

USB to Serial (DB-9) converters range in price from about $10 - $20 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 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