Al Grippo and Bruce Bowling have created on MegaSquirt-II, which is a plug-in daughter card which replaces the MC68HC908GP32 with a MC9S12 processor. MegaSquirt-II is an "intermediate" step from the original V1 and V2.2 MegaSquirt towards UltraMegaSquirt. It is basically a plug-in processor card which has the MC9S12 processor plus support hardware as well as a stepper motor chip, and an ignition module controller.

You simply remove the 68HC908GP32 processor on your existing MegaSquirt and plug in the MegaSquirt-II daughter card and their MegaSquirt is now a MegaSquirt-II - it takes less than a minute to do.

MegaSquirt-II has the following features:

• 24 MHz HCS12 processor (C32 or C64 version),
• Fuel control to 1 µsec (100 times more resolution than MegaSquirt),
• Ignition control (full spark timing advance control, dwell control, etc) for one coil/distributor (7 pin HEI for example) and Ford's EDIS systems,
• On-board stepper motor driver for IAC stepper control (this requires a few jumpers to be added on the MegaSquirt PCB to connect the socket jumpers to the DB37 connector),
• Ford PWM idle valve support,
• Built-in rev limiter, either 'fuel cut' or 'spark retard',
• All tables are now 12×12 in size,
• WBO₂ AFR target table (in AFR units),
• Independent dual-tables for VE and AFR target,
• EGO feedback in wide-band mode is proportional to the difference between the measured AFR and the target AFR, the bigger the difference, the bigger the feedback step,
• Spark advance table can have different rpm and kpa bins than VE and AFR tables,
• 115,200 baud serial interface with MegaTune2.25+,
• CANbus networking *may* be added in next revision of hardware,
• Barometric correction amount and direction configurable in software, and provisions for:
  • barometric correction based on initial MAP reading,
  • independent 2nd barometric MAP sensor for continuous real-time baro correction, or
  • no baro correction.
• TPS values for open loop and flood clear mode are user configurable,
• MAP based open loop can be set as well as TPS,
• Both TPS and MAP based accel enrichment is built into the code, you can configure the ratio of each,
• Blended Alpha-N and speed density is an option,
• 2 spare I/O lines for custom controls. (This is in addition to 4 lines for Idle stepper control if you don't need this, or the Fast idle solenoid then becomes a spare if you do use a stepper motor.)
• Very inexpensive (~$75 US).

The processor is from the Motorola HCS12 family. It has plenty of excess capability and is a 16 bit machine allowing as much timing resolution as anyone can practically use. Since it is in the Motorola family the MegaSquirt embedded code will port over quite easily, however the MegaSquirt-II code has been converted to the C programming language since there is a free GNU cross-compiler for this CPU. This will make it much easier for others to customize the algorithms to meet their needs.

The MegaSquirt-II daughter card plugs in to the existing MegaSquirt processor socket, replacing the MegaSquirt 68HC908 processor.

The reason for this intermediate step is that everyone with an existing MegaSquirt system can pull out their processor and plug in this board and they will have the UltraMegaSquirt code. This will allow people to test the UltraMegaSquirt code on real vehicles while we work out the details of the FPGA routing and switching and multiple I/O that will come with UltraMegaSquirt.

The main differences between MegaSquirt-II and UltraMegaSquirt are that there is:

• Limited flexibility for input and output (same as current MegaSquirt),
• Only 1 NB-O2/WB-O2 channel (no built in WB heater/driver support, WBO2 requires a separate controller),
• No Controller Area Network (CAN), and
• Hardware doesn't support sequential injection.

MegaSquirt-II Features

MegaSquirt-II adds the following enhancements over MegaSquirt:

1) Processor: When MegaSquirt was started almost three years ago, the best bang for the money was the HC08 family (also Atmel and Microchip). In three years, looking at the next step range of processors, the family that stands out is the HC12/HCS12.

2) Existing software: The goal of choosing a processor is to try to keep the current established code operational. With the HC12 family, it is extremely easy to modify existing assembly code for this processor - it amounts to about a two hour effort, without taking advantage of the HC12 architecture. And, if people want to code in C, there is a good GNU GCC toolchain available for writing and modifying code, as well as Metrowerks Codewarrior.

3) 12 x 12 Tuning tables: for Volumetric Efficiency (VE) table, 12 x 12 for Air Fuel Ratio (AFR) table, and 12 x 12 for Spark Advance table. There are separate AFR and VE tables for each injector bank (similar to the dual table code),

4) Stepper motor IAC control: for most common EFI idle control motors, as well as support for MegaSquirt's FIdle valve control and the Ford PWM idle valve.

5) Ignition Control: MegaSquirt-II code has the ability to control ignition (including dwell control). It supports 1 coil/distributor configuration, and the Ford EDIS 'wasted-spark' system.

6) 3 spare I/O lines for custom controls. (This is in addition to 4 lines for Idle stepper control if you don't need this, or the Fast idle solenoid then becomes a spare if you do use a stepper motor.)

7) 115200 baud serial communications rate (vrs. 9600 of MegaSquirt).

How to Buy MegaSquirt-II Hardware

The price for MegaSquirt-II has not been determined yet, but it is expected to be about $75 (US).

The final price will depend on the cost for having the surface mount components soldered on. The printed circuit board is much smaller, but it is a 4 layer board, so that will probably be similar to the MegaSquirt board's cost in large quantities (but much more expensive in small quantities.) The parts themselves are probably cheaper.

MegaSquirt-II is an add-on option for a standard MegaSquirt. To learn more about MegaSquirt, go to the MegaSquirt FAQ and manual. The assembly, testing, and installation of MegaSquirt is covered at those sites. This site deals only with the MegaSquirt-II add-in board.

The MegaSquirt-II can be ordered as:

• a MegaSquirt-II partial kit (which includes the MegaSquirt-II processor daughter card, MegaSquirt PCB, MAP sensor, and FET driver, but not the 68HC908 processor),
• or as a MegaSquirt-II 'upgrade' daughter card to replace the 68HC908 processor in existing MegaSquirts.

There may eventually be just the bare PCB sold for those who feel undaunted about surface mount soldering, but initially only the first 2 options will be sold until we have a good user base and know the system is reliable when soldered professionally.

The ordering page is at:

If you are starting from scratch, in addition to the MegaSquirt-II partial kit, you'll need the Digi-Key BOM of parts, and a case and other small parts (the stimulator is highly recommended). If you already have a working MegaSquirt, you only need the MegaSquirt-II add-in board.

Full installation instructions are at the MegaSquirt-II installation page.

There is also a huge amount of collective experience and knowledge related to the assembly and installation of MegaSquirt/MegaSquirt-II in various vehicles available on the MegaSquirt Forums website.