[Efi332] H/W - S/W Question about triggering MSD type ignition box

[Paul Helmuth]

All (all three of you),

I have be swapping some email with Jeff to get some idea of where each of us were in the development process. Development that is, of projects similar to the original EFI-332 project, but based on the MPC555 chip (and in particular on the Phytec SBC - though I am not utilizing any resources that aren't directly on the MPC555).

Per my exchanges with Jeff, I'm posting this query to the list.

I am pretty close to doing some "ignition trigger only" testing, but would like to check a few things with some of you that have more experience than I.

1) I have set up individual TPU channels with the PSP12 function to generate the timing pulse for each of the cylinders. I have set them up in the Angle-time mode. This seems most appropriate since the external trigger isn't controlling the "dwell", just providing a timing signal. I'm reasonably confident of this, but if I'm wrong, please set me straight.

2) In order to provide the timing signal to the external ignition box (in my case a Crane Fireball system), I need to ground one of the wires going in to the control box. Since I have one TPU pin for each cylinder and I want to use the high signal from each of them to "energize" the base of a transistor (in order to "switch on" a connection to ground) - do I need to "isolate" the individual TPU pin outputs (like running them through an OR gate, or putting diodes in between each pin and the transistor base) or can they all be directly connected to the transistor base? My first concern is any potential damage to the TPU channel pins. Secondly, I wonder if having all of them common would effectively "pull down" the high signal that each of them will be generating in sequence.?.?

Thanks,
Paul
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