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General Purpose Input/Output Board Hardware

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This is the general assembly and troubleshooting guide for the GPIO board from Bowling and Grippo. If you are looking for application related advice/instructions, see:

The general purpose input/output (GPIO) board is an expansion board for MegaSquirt-II™ and related controllers. It provides a number (up to 25) of additional inputs and outputs for MegaSquirt-II. The additional I/O lines are communicated over a CAN (controller area network) which allows communication between the GPIO and MegaSquirt-II™. This allows there to be just two wires connecting the MegaSquirt-II™ and the GPIO, while still sending any number of I/O signals.

The 'features' of GPIO are:

The serial connector is NOT the primary connection to the system, most communications (everything other than re-flash) will typically be done over CAN to the main board, including configuration and datalogging.

Unlike MegaSquirt® EFI Controller, the GPIO Board does not use a DB9 connector for serial communications. Instead it uses a 2.5 mm (aka. 3/32") sub-miniature stereo jack, of the same spec used for the Innovate LC-1 wide band controller:

This cable is supplied with production GPIO units, but not beta units. If you have a beta GPIO board, or if you have lost your cable, you can build it from Digi-Key parts. To build this cable (if you don't already have one):

Solder the leads from the 2.5mm stereo plug cable {Digi-Key CP-254CS-ND} to the DB9 connector {Digi-Key 4109FE-ND}. The wires are soldered to the pins as follows:

Wire ColorDB9 Pin
Yellowno connection

Note the the pins are numbered on the face of the DB9 (they are imprinted in the plastic), and the pins go straight-through to the solder cups. See the illustration below for clarification.

You can make your own serial cable, the illustrations below might help.

This was done because the serial connection is used much less frequently with the GPIO board than with MegaSquirt® EFI Controller, and it allows the serial connection to be sealed.

Optionally, the serial connections can be brought out through the weather sealed Ampseal connector. There are pads labeled Tx and Rx adjacent the serial plug location on the PCB.

The connections are:

©2006, 2012 Al Grippo and Bruce Bowling and Lance Gardiner - All rights reserved. MegaSquirt® and MicroSquirt® are registered trademarks.