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Note: The EFI332 project is defunct, and these pages are no longer being actively maintained.

Other Info

Two Layer Design

Four Layer Design

Board Layout Sketches
Actual Board Scans
Common Assembly Questions
Semiconductor Datasheets
Case Construction Sketch

Ignition and Injector Driver Boards

The Current 4-Layer Board

This page describes the current version of the Electronic Fuel Injection (EFI) control board under development by Bruce Bowling and Al Grippo. This board, denoted as the "4-layer EFI" board (mainly because the circuit board consists of 4 layers: one power, one ground, and two signal), is the current incarnation of the efi332 project. This board consists of the following sections:

Embedded Controller

The CPU section is based on a Motorola 68332 microcontroller, and is similar to the CPU board section of the EFI332 board (designed by Rod Baram). This microntroller contains on-board analog-to-digital converters and a sophisticated Time Processor Unit. The CPU section uses flash and non-volatile SRAM memory devices for program and data. This section is the heart of the 4-layer EFI board.

Sensor Input

The Sensor section consists of the analog and digital circuitry required to condition the various input measurement devices, which include:
- Air Temperature
- Engine Coolant
- Manifold Air Temperature
- Barometric Pressure
- Throttle Position
- Battery Voltage
In addition, there are several spare A/D channels available for user applications.

Fuel Injector Output

This section provides the line drivers for an off-board fuel injector power board. The timing for the injection pulses are generated by the TPU section of the CPU. There are eight separate drive lines which can serve one or more injectors each.

Spark Ignition Output

This section provides the drive circuitry to trigger an off-board ignition driver board. The calculations of trigger events and dwell is performed by the TPU in the CPU section. There are two signals associated with this section - one which is the trigger for the ignition event, and another which serves as a sync reset which denotes cylinder number one (this is used by the ignition driver board).

Power Supply

The power supply section provides the required voltage regulation for the semiconductor devices. In addition, this section provides protection from abberations on the vehicle's electrical system, including noise spikes, polarity reversals, and brownouts, as well as filtering noise which are always present in an operating vehicle environment.


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Schematic Diagrams

CPU Section
Input Section
Output Section
Serial Communications Section

Board Layout Scans

Overall Board Layout
CPU Section
Analog to Digital Conversion
Crankshaft / Camshaft Conditioning
Power Section
Octal Serial Output Driver
BDM/Serial Communications
Configuration DIP switch
Input/Output Connector
Stepper Motor Drive (New)

Actual Board Scans

Scan of Lower Front of Board - Processor Area
This area of the board shows what parts are needed to test the operation of the CPU section. Above the processor socket area is the crystal and associated components, like the resistor packs (click here to see a close-up). To the right of the socket area is a decopuling capacitor (the holes for this component can be a little tight - be sure to use the smallest form factor possible). Below the processor area and to the right is the power supply section and serial driver chip - assembly is straightforward (click here to see a close-up). To the left of this is a DIP switch, a few diodes, and a resistor pak. Not shown but directly above the processor socket is the SRAM and Flash socket areas - each have a decoupling capacitor directly to the right. Also, the top Flash part has a tantalum capacitor and resistor.

The board assembler has a choice on which side of the board to place three specific capacitors. These components are right in the middle of the processor socket. Al was able to use small components and place them on the topside of the board, underneath the processor socket. The monstorous capacitors that I had forced me to mount two of them on the backside of the board and one under the socket. It really does not matter which side of the board the components are mounted.

Scan of Lower Rear of Board - Processor Area
There are a few surface-mount capacitors which are mounted on the back of the board around the processor (click here to see a close-up). To mount the SMD components, I first tinned the pads with solder, then I laid the component down and then tipped each side with the soldering iron to secure, finally I went over the component with more solder. The SMD components are the most tricky - once you get these mounted up, the rest of the board is easy...

Scan of Rear of Board - Lower Region
Here you can see the two capacitors in the middle of the processor socket area - the third cap is mounted on the top side under the processor. You can also see that I need to de-flux the board.

Scan of Front of Board - Most of Board
Here is the board with the all sockets installed. In addition, several integrated circuits are also installed, including the A/D converter chips in the upper right, and all of the associated components. Be sure to look closely at the assembly drawings for the A/D channels - there are several spare channels which are tied to ground via. jumper wires (to reduce channel crosstalk noise). When one needs to use a spare A/D channel, snip the jumper and put in a suitable resistor/cap combination for the application.

Scan of Back of Board - Most of Board
Here you can see the other surface-mount capacitors mounted over the A/D section (to the right middle of the picture, just to the left of the 37-pin socket). It might make sense to mount these early on, when you mount the other SMD components.

Scan of Front of Board - Board Under Test
Here is a picture of the entire board, connected to a laptop computer via. a commercial BDM cable. The wire that is soldered to the power supply section is only temporary (for quick testing) - the +12 volt vehicle power is presented via. the right-hand DB37 connector in the final application. The only things not on this board is the stepper motor chip (which is the new circuit using the UDN2916B) and the 2N2222A transitor/base resistor in the lower-left of the board.

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Common Assembly Questions

Scavenged from posts to the list:

Q1. The PDF schematics don't show a pullup on the RESET line that I     can see, but it is there on the hand drawn schematics from Bruce/Al.     The value is very hard to read. I guessed and put a 10k and it seems     to work fine. Does value really matter? This one is particularly     important since without it, the BDM won't even work correctly.

A1) 10k will work fine.

Q2) In my parts kit and on Bruces parts list, there is a Reset supervisor.     Where does this go on the board? It's not on the PDF schematic or     the hand drawn one that I can see.

A2) It is on the hand-drawn picture, under the "BDM/Serial Comminications"     link:


    Its the MCP120-475DI part.

Q3) There a few components missing on the PDF schematic which are on     the hand drawn schematic. The are two fairly important caps which go     underneath the processor for the PLL. These caps can make or break a     board. Trust me - we have had problems with Motorola PLLs that even     Motorola didn't even have a straight up answer for.

A3) Use the hand-drawn pictures for assembly. And these caps *are*     show-stoppers indeed!

Q4) A while back Bruce said "Be sure to put the rubber spacer over the CPU     socket BEFORE you solder the socket to the board. If you fail to     do this, then throw the board in the trash, because it is next to     impossible to remove the socket."  when it came to making the 4     layer board.

A4) This plastic piece, which is only pushed halfway on the socket pins,     is used to keep the pins from being bent during shipping, AND is     used as an insulator for the socket - just push the plastic piece     flush with the socket. You can see how the pins bend all which ways     under the socket and this piece keeps this insulated from the board.     Since there is a soldermask on these boards if one forgets the spacer     the board *may* still work, but it will be by luck only.

Q5) Does the flash (am29f010) have to be 70 ns or could I use 90 ns     parts ??  I have lookt though the 332 datasheet without finding an     answer (I have some 90 ns laying around I would like to use)

A5) 90ns will work, but you will have to increase wait-states.

Q6) Charles' BDM board notes say that pin 1 of the small connector is     on the left when facing the connector.  It appears to be the same     on the 4-layer board, i.e on the left when facing the connector.     Is this correct?

A6) Al *always* uses a square pad to indicate pin 1 on sockets, plugs,     etc, and the hand drawings also will always show a square pad for     pin #1.

Q7) the diy-efi site is missing the files octser.jpg and step.jpg.  I was     able to find step.jpg at Al Grippo's page but not octser.jpg either.     Can someone make these available please?  The assembly of the output     section should be simple but is not obvious without these diagrams.

A7) First, there was a bug in the 4-layer page in my HTML (Bruce left off     a ") which made some of the links not appear, specifically the     octal serial and buffer scans.  This is fixed now. Also, the octal     serial page also shows the OLD stepper motor chip. Remember that the     stepper motor chip was replaced with a newer chip, and this layout     scan is on a separate link page (the "Stepper Motor New" link).     The WWW site has a warning about this.

    Also, the WWW page is now at http://www.diy-efi.org/~bbowling   -     Bruce updated this page only. Do not use the old sura1.jlab.org link     anymore.

Q8) What is the function and normal positions of the DIP switch block?

A8) Only one switch contact (the far left one) is used, which is used     by the software to see if either a laptop (running the mainpc.exe     monitor program) or if a LCD/button box (used as a passenger     compartment monitor - this device is a 2x20 line LCD and a serial     backpack encased in a small box) is connected to the serial port.

Q9) From the schematic, the stepper chip has a 3 pin header/jumper     nearby.  My parts kit did not include any headers or jumpers.     Was this an omission?  If it is supposed to be there what is its     function and what is the normal position of the jumper?

A9) The jumpers are used for different operating modes of the stepper     motor chip (like PWM current limiting control, etc). The position     of the jumper is really dependent on your end IAC motor. One thing I     strongly suggest is to download the datasheet for the stepper motor     chip - the functions of the jumpers will become clear. There are     also jjumper blocks around the LM1815 chips to allow either VR or     digital signals.  Once again, look at the datasheet for the different     operating modes.

Q10) Where do the 1 ohm, 1 watt resistors go?  I have not come across      them in the sketches or schematics.

A10) Around the new stepper motor chip, which you will see on the      now-fixed WWW site.  This value affects the operation of the      current-limit, and you may want to adjust its value - see the      datasheet to understand this better.

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Semiconductor Datasheets

DS1245Y-70 Battery-backed SRAM modules
AM29F010 Flash
UDN2916B Stepper Motor Driver
MAX232A RS-232 Driver
MC145051P A/D Converter
MC33298 Octal Serial Driver
LM1815 Variable Reluctance Sensor Amplifier

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Note: The following information is for educational purpose only - no liability is assumed by either Bruce Bowling or Al Grippo for implementation of the EFI system in whole or in part.

Bruce A. Bowling - bbowling@earthlink.net
Al C. Grippo - grippo@jlab.org
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2-Layer CPU Board Design v0.4

EFI332 v0.4 was the first CPU board designed for the EFI332 group. It is a two layer PCB, with support for 2 29f010 flash memory chips and 256K of SRAM. It has been superceded by the 4 layer board designed by Bruce Bowling and Al Grippo.


Parts list:


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Ignition and Injector Driver Boards

To be populated with files and info on the two driver board designs out there




For problems or questions regarding this collection of webpages contact bowtievette@aol.com.

Thanks to Bowling & Grippo for their financial support of this site!