Which MS do I want?
09-27-2010, 04:45 PM
#41
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The pretty pictures say things like "Good engine ground", however I can't find any discussion anywhere of which pins on which connector are which ground. Nothing tells me "The injector drivers go to ground through pins x, y and z of connector A, while the medium-current relay drivers go to ground through pins x and y of connector B. All analog grounds are isolated to pin x on connector C. A polyfuse conjoins ground planes X and Y at such-and-such point, and may be removed if you experience noise-coupling into the analog sensors."
I also see absolutely no mention of injector grounding on the "Fuel System" page, and no discussion of the underlying hardware in the "Ignition System" page. The one thing I do see here is that "for 99% of installs you should set Spark Output to "Going high (inverted)" with absolutely no discussion of what this actually means, or the fact that, in reality, the "Inverted" setting is NON INVERTED.
I also see absolutely no mention of injector grounding on the "Fuel System" page, and no discussion of the underlying hardware in the "Ignition System" page. The one thing I do see here is that "for 99% of installs you should set Spark Output to "Going high (inverted)" with absolutely no discussion of what this actually means, or the fact that, in reality, the "Inverted" setting is NON INVERTED.
In fact, I only just now realized something (Depending on how much "not like" the sequencer the MS3X isn't.) They could have avoided the need for any software foolishness in the bootloader (and achieved a properly Fail Safe configuration" by pulling those lines (between the CPU and the 74ACT541) weakly to ground rather than weakly to +5. The MC9S12 can source just as much IO current as it can sink, so that would have left the circuit "inverted" but prevented the outputs from going high when the CPU was not in control of them.
The inverted vs non-inverted output terminology goes back to when the LED-style outputs were "normal" and connecting to VB921 or other IGBTs were "inverted." I've already discussed changing the naming there with James to make more sense.
Ken
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09-27-2010, 05:40 PM
#43
Boost Pope
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If you are not using the MS3X, and instead wiring your ignition drivers off the outer LEDs on the 3.0 / 3.57 board, and you're using my "improved" (double-inverting) output driver, then you will set spark out to "Inverted" (which is non-inverted) just like you would with an MS1 or MS2.
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09-27-2010, 05:59 PM
#44
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Going back to the VB921 design, a positive voltage applied to the "input" terminal of the 921 from the CPU causes the 921 to turn "on", which allows current to flow through the coil.
In such an environment, one must set "Spark Out Inverted" to "Yes."
Do you have any recollection of what the rationale behind that nomenclature was? To me, the word "inverted" would imply something other than the "normal" method of operation, which even back then was for the CPU to raise one of its output pins high when it wishes for the coil to operate. From the CPU's point of view, "high" = coil on, and "low" = coil off. And yet that is what got called "inverted".
In other words, my "improved" spark driver works precisely the same way as the very first ignition-capable Megasquirts did. And yet in both systems, "inverted" means that the ignition coil follows the state of the CPU output pin controlling it, rather than being inverse of it.
I've never understood why the nomenclature was written that way. It only makes sense if the "inverted" vs. "non-inverted" nomenclature wasn't coined until people started using the LED circuits to drive wasted-spark coils with on-board igniters, in which case (assuming the "standard" circuit) the "non-inverted" nomenclature makes sense, not from the point of view of the CPU, but from the point of view of the inverting output driver.
But as you said, the term supposedly predates this.
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09-28-2010, 09:42 AM
#45
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I've never understood why the nomenclature was written that way. It only makes sense if the "inverted" vs. "non-inverted" nomenclature wasn't coined until people started using the LED circuits to drive wasted-spark coils with on-board igniters, in which case (assuming the "standard" circuit) the "non-inverted" nomenclature makes sense, not from the point of view of the CPU, but from the point of view of the inverting output driver.
But as you said, the term supposedly predates this.
But as you said, the term supposedly predates this.
It is a bit strange that this same confusion carries over into MS2. The reason is a little different there - the original (pre-CANBUS) MS2 design had a small transistor on the spark output that was dropped from later versions.
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