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Introduction to the MicroSquirt® Module EFI controller

MicroSquirt® encapsulates pretty much everything that MegaSquirt® has to offer, in a board the size of a business card. It would be nice to have this package for a true DIY setup…

For real engine experimenters, the MicroSquirt® PCB is offered in a module format - The MicroSquirt® Module. Retailing for $249 (as of this writing), the MicroSquirt® Module is intended to be used to plugged into other boards, to let others add things like:

There are some potential add-on circuits for the MicroSquirt® Module described here.

The MicroSquirt® Module has exactly same circuits as MicroSquirt® (except ignition drivers, which are logic-level output only). Module is only 2.4 inches wide by 3.5 inches long – credit-card sized! The Ampseal 35-pin connector is replaced with a 0.1” header, with two rows of 25 pins (25x2). All input and output connections are present on this header.

You can find the MicroSquirt® Module schematics here:

MicroSquirt® Module J2 25x2 Header Pin-out:

1, 2+12V Battery
4Serial Rx
6Serial Tx
14VR In2(+)
16Spare ADC2/MAF Pin
17Spare ADC1
19Opto In(+)
21Opto In(-)
22Fuel Pump
23VR In1(+)
24, 26, 28, 30, 32INJ1
25VR In (-)
29Tach Out
31Serial Ground
33Sensor Ground
35, 37, 39, 41, 43, 49Power Ground
34, 36, 38, 40, 42INJ2
44, 46IGN2
48, 50IGN1

Example 25x2 receptacle header – Tyco/Amp 7-534206-5
Matching 25x2 pin header – Tyco/Amp 9-146254-0-25

MicroSquirt® Module J1 5x2 Header Pin-out:

Additional processor I/O brought out on J1 5x2 header (J1):

3, 5Ground
4Alternate INJ1
6Alternate INJ2
8Alternate CAM
10IAC enable

Also available for the MicroSquirt® Module is a standard adapter board, the "MicroSquirt® Utility Board" that connects the 25x2 header to terminal strips to allow a very compact, easy to connect package for the module:


This board mounts to the mounting holes in the module, using stand-offs:


  1. The female 25x2 receptacle goes on the processor side of the MicroSquirt® Module (the side with all the SMT components on it).
  2. The header for the utility board has 26 pins (2x13 headers). To line up the pins, the extra pair of pins goes to the 'GND Pwr' 4 position terminal block/'proto' end of the board assembly, so the connections are correct and the board mounting holes line up.

MegaSquirt® and MicroSquirt® controllers are experimental devices intended for educational purposes.
MegaSquirt® and MicroSquirt® controllers are not for sale or use on pollution controlled vehicles. Check the laws that apply in your locality to determine if using a MegaSquirt® or MicroSquirt® controller is legal for your application.
©2009, 2011 Bruce Bowling and Al Grippo. All rights reserved. MegaSquirt® and MicroSquirt® are registered trademarks. This document is solely for the support of MegaSquirt® boards from Bowling and Grippo.