Guys, I have been really busy. Broken car, lots of work, etc.
Jharvey, I have not reviewed your schematic recently. If I remember from looking at it previously, there were hall sensors on drivers and such which are all good, but add components and complexity that most of us will not want/need. Most of this is not 'developing the circuits', but developing the firmware to run cars. The rest of the circuits are well understood and well tested. I vote we creatively re-purpose simple circuits that are used elsewhere in the field. I have nothing against an alternate to the LM1815, but suggest its use as it is well known and has been used for years on VRs with no issues in the Saab ECUs I am familiar with.
Low current drives should all be 2n2222 or equivalent and should be able to be used as I or O. Most should have a readily available 5V pullup on B and C. I am not against using fets here, either, but I have experience with 2n2222 and BS170 (fets). Also if a 12V pullup is needed, it should be able to be done with a jumper wire. I am not against soldering this across as it will be only on a few outputs (tach, drivers for external control devices) that will need 12V vs 5V. All hall sensors must be used with 5V reference. Using a noisy 12V reference for these is just not a good idea. An alternate tested suggestion would be to use a chip for this which provided 4 outputs at a time. One is a CA3236 which is used in Saab trionic ECUs to trigger the ignition, 4 outputs. I have not found a data sheet on this one, though, and it appears hard to find. A multi I/O chip with similar to 2n2222 or BS170 capability would be a plus as board consumption would be reduced.
The one thing that has been discussed but not fully agreed upon is the injector drivers. I know that there are many MS units running vnd5n07 directly off the micro pin (without fet driver). Based on this experience, I am willing to go with this for initial boards. Personally, I feel it is 'better' to have fet drivers and that is why I am running them on my install. I have not verified any of this, but can look closely at my Saab ECU and see how it is driven. It uses MTD3055s for injector control.
http://www.datasheetcatalog.org/datashe ... 55VL-D.PDF. I will check tonight to see if these are driven by FET drivers, but they are also logic level FETS and avalanche rated, so they may also be driven directly by the micro. If so, I would endorse this direction as it minimizes parts and these are dead reliable.
Lets start a requirements list and make sure we hit these or strike them from the list.
Requirements:
1) Power supply
2) 6 analog inputs (CLT, MAT, TPS, MAP, TP, Batt)
3) 6 injector outputs
4) 6 low current ign outputs *no high level coil drivers on board, these should be separate*
5) Separate ground plane for digital, analog and high current
6) Separate battery sense 12V line which is not used to power any of the ECU components
7) Grounding to be done by low impedance cable (large size) to the block for each ground plane. (These can be jumpered together at the board at your own peril.)
8) No LowZ injector drivers on the board. If you want to put in a header to drive Jean's boards, I am fine with this as there may be people trying to run FreeEMS to develop it with LowZ injectors
9) Extra high and low current drivers which can be used as either I or O, have 5V digital nearby for pull up. 12V pullup does not need to be as easy to get, but could be used in the case of certain I or O.
10) no current sensing needed on board as part of layout. KISS
Any more Requirements?
Gearhead