Assembling Serial IDC to DB9 Cable

Applicable for

Iris Carrier Board | Ixora Carrier Board

Article updated at 15 Jul 2022

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Assembling Serial Adapter Cable

In order to connect the RS-232 from the Iris or Ixora carrier boards to a DB9 connector, you must assemble a 10-pin IDC to DB9 adapter. The following steps will guide you through assembling your adapter cable.

You may buy one adapter, paying attention to the standard - usually called DTK or Intel standard. It is available in the Carrier Board Accessory Kit and from many electronic components suppliers, e.g. here.

Bill of Materials

You will need:

10-pin IDC female connector
10 way ribbon cable (>10cm)
DB9/D-sub female connector (preferably a 10-pin IDC to 9-pin D-sub male connector)
Solder wire and soldering iron, depending on your DB9/D-sub connector

Note: you may use another cable type and length, depending on your preference

The image below presents the bill of materials required for the adapter:

Serial adapter BOM

Verify the UART pinout

Verify the pinout of the carrier board pin header and the serial DB9 connector.

IDC pinout

DB9 pinout

Warning: The TX from the IDC header must be connected to the RX from the DB9 connector. The RX from the IDC header must be connected to the TX from the DB9 connector.

Crimp the IDC connector

Crimp the ribbon cable to the IDC connector.

Crimped IDC connector - top view

Crimped IDC connector - bottom view

Note: It might be interesting to define a pattern in this step such as always having the ribbon cable to the left of the even pins of the connector, since the carrier board does not have an IDC header to prevent inverted polarity, but instead only a pin header.

Crimp the DB9 connector

If you have an IDC to DB9 connector, also crimp it paying attention to the pins correspondence.

Crimped IDC to DB9 connector

Beware that you may either:

Invert the Tx and Rx pins, or;
Use a null modem cable/adapter, or;
Use a serial to USB adapter that accepts configurable Tx and Rx pins.

Note: if nothing appears on the serial terminal emulator, consider the hypothesis that Tx and Rx pins may be inverted.

Strip the ribbon cable

If your DB9 connector needs to be soldered, do it only for the Tx, Rx and ground pins. Strip the ribbon cable:

Warning: customers reported issues if all pins are connected, therefore we recommend that you only solder the Tx, Rx and GND as described in the upcoming instructions.