VID/YAG update

Good Morning.

I am still testing the changes I made the other day in regard to the bug I reported. However, I also decided I better get some of code changes entered to support peak&hold type injectors. Of course this compounds the testing effort. However, it is interesting how fixing a bug leads to other improvements in the program. It is of course, still one step forward, 1 1/2 steps back. most of the time.

The Windows host configuration dialog now allows the user to select whether the VID responds to negative going or positive going fuel injector pulse information. In most cases, the vehicle's ECU pulls the injector to ground.-- so the VID's default for this, is negative going. In some cases, however, (I understand that some) ECUs pull the fuel injector up toward battery voltage.
This change, handles that contingency.

Both the VID and Windows host program also now allows the user (me) to enter values for the high and low limits for the injector input comparator. Again, in most cases both values would simply be set to mid-range and forgotten. However, in peak and hold cases, the values entered would be more like 1 and 15. This effectively, allows the VID to alter the input switching threshold from about 2 volt (for the negative going edge) up to about ( 10 volts actual) volts for the positive going edge. (Internally, the actual injector voltage level is scaled down into a range of about 1-3.3 volts to comply with CPU voltage reference constrains.) I believe this would allow the device to accurately profile the two step pulse width of the peak and hold type fuel.injectors.


In this shot, the blue trace represents the CPU controlled reference voltage--ranging from about 3 up to about 10 volts. The blue line illustrates the falling edge of the injector input--ranging from 12 down to about 0 volts. Notice how the blue trace changes from low state to high state following the transition of the injector trace. I don't have a trace of what an actual peak&hold injector would look like (in real life). However, an educated guess is, that once the ECU pulls the injector line to hard ground, unless the comparator reference voltage is immediately switched to a much higher level, the output pulse width (seen by the CPU) will be truncated when the ECU relaxes its hold on the injector--and not, when the injector is switched off. Therefore, in my application, the reference voltage moves up to above the "hold level" of the injector, and waits for the ECU to switch the injector--fully OFF...i.e. returning to 12 volts. In this fashion, the entire pulse width of the peak and hold injector is captured.

The design of the injector front end is trying to make it possible for the card to be adapted to almost any vehicle situation. I plan to make it very easy to change resistor and capacitor values in the field. This should--- make it flexible enough for most technical types to get this thing working with a minimum of fuss.