Edis Ignition/Software Module - VEMS wiki www.vems.hu

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

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

static inline void edis_saw(void)
{
	uint16_t t, saw_length;
	edis_saw_high();
	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;
	else
		saw_length = MAX_SAW_LEN - t;

	event_insert(etime.now + saw_length, EDIS_STOP_SAW);
}

This shows the power of GenBoard:

edis_saw_high(); is a simple port-action (it can be specified compiletime if SAW is wired inverted or not, so it's 3 lines in fact)
The sawlength calculation is basicly one line, a 16*8 multiplication (this had been split to be calculated from userspace - not interrupt - and sawlength stored in the dwell variable. Also, multispark capability was added (configurable).
the if condition takes care if the user configures too high ignitionadvance (edis max is 57 (??) degree, while msavr ignition table defaults to 1/4 degree ignition advance from 0..64 degrees.)
the event_insert() uses the EventQueue to schedule an event, which will call edis_saw_low() a specified time (saw_length * 4 usec) later

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

NAPA ONLINE lists:

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]