See EdisIgnition/FaQ for how to connect EDIS module to GenBoard

See firmware/edis.c to see how edis support is implemented in GenBoard

Here is an [online version]

static inline void edis_saw(void)
	uint16_t t, saw_length;
	t = mult16_8(410, engine.ignadv)>>8;	// 410 comes from: 25.6*16
 define MAX_SAW_LEN (1536/4)
 define MIN_SAW_LEN (20/4)
	if((MAX_SAW_LEN - MIN_SAW_LEN) < t)
		saw_length = MIN_SAW_LEN;
		saw_length = MAX_SAW_LEN - t;

	event_insert(etime.now + saw_length, EDIS_STOP_SAW);

This shows the power of GenBoard:

It's called from the interrupt, which happens at the falling edge of PIP.

It's that simple.

Kenny Bauman kennybauman at yahoo.com writes:

The ford EDIS is a standalone microprosessor based ignition. It handles all timing calculations and trigger wheel processing internally. MS AVR only has to deal with a SAW and PIP signal to make the EDIS setup work.

What happens is the EDIS sends out a PIP signal that will tell MS AVR it needs a SAW in return. The length of this SAW signal tells EDIS what timing is desired.

If EDIS looses the SAW signal it defaults to 10 deg timing as a base value. Nice as a built in limp home mode.

Makes a nice setup as it is proven and hardened for the underhood environment.

Regarding the 36-1 trigger wheel. This has to be a Crank trigger not a cam trigger. You can use a cam trigger, but it needs to be 36-1 and 36-1 on the same wheel for a total of 72-2 teeth. The missing teeth would be 180 degs apart. This is for EDIS.

So what I "think" is needed is a interrupt (or event que) every time EDIS sends the PIP signal. Go to the lookup table get the timing value stored, do the math and then send a timed pulse back to EDIS as the SAW signal. That's it. EDIS takes care of all the hard stuff.

SAW (microseconds) = 1536 - (25.6 * Commanded_degrees)

You can go to: http://www.bgsoflex.com/mjl/mjl_edis_summary.html

to see more about the relationship of PIP and SAW.

Here are some AC Delco part numbers for the EDIS-4 module and the coil. The US model vehicle is: '93 Escort LX w/1.9L 116CID L4 MFI (J) engine.

EDIS Module - AC Delco F1945

Coil AC - Delco F510


Echlin Ignition Ignition Control Module ECHTP500

I haven't found a part number for the VR pickup and then there is the toothed wheel.

Some more trigger wheel info-

James Murray at james@nscc.info has part numbers and excellent pictures here.

[North America]


And this may be of interest to some test bench work or engine retrofit.

[Zip file of GM sprag data]

Jay James

Another good intro:


Note, that the postion of VRS pickup sensor in relation to TDC of cylinder 1 is not the same for all EDIS modules:

Cylinders Degrees BTDC

EDIS4 90

EDIS6 60

EDIS8 50

[[Manual: Detailed.Output.EDIS.Install]]

Jim Hearne

[[Manual: Detailed.Output.EDIS.Install]]

Dave Haynes

[[Manual: Detailed.Output.EDIS.Install]]

See also: IgnitionPage IonSense

[[Manual: Detailed.Output.EDIS.Install]]