Building the Brains for a Budget Racer: Jaguar A7 #42

[Fred]

https://mobile.twitter.com/FredCookeNZ/ ... 0879196160

[m2cupcar]

I did the InjIN-cpu jumpers wrong (covered ports) - didn't view your pics until after. Not so much impatience as taking advantage of some available time. Got carried away installing leads last night, only to realize I should have limited that to ground/power leads THEN powered to observe the benchtest firmware run. Leads left to install: IGN-12V, Ignition-1, Ignition-2, and Injectors 1-4.

[m2cupcar]

Configuration details:

• Ports T4-7 connected to corresponding Injector-IN ports
• JP3, JP4, JP5 injector jumpers installed
• INJ1-GND and INJ2-GND leads connected
• INJ4-GND jumped to OUPUT-GND
• HSD-FP jumped for stock Miata fuel pump relay trigger
• LSD2/PK4 jumped for coolant fan activation using stock Miata fan relay
• Installed 1K 1/4w resistors at R16, R17, R18, R19 and R20/R23 left vacant, connected RPM0- to RPM0-Shield and RPM1- to RPM1-Shield for stock Miata CAS
• Jumped JP1 to 12v for stock Miata coils

[Fred]

Great progress :-)

You need that ign-12v hooked up to see the LEDs glowing with bench test. All those flying yellow wires on mine are grounds and 12v and 5v to allow bench test with just USB connected.

Don't worry about the jumpers covering the holes, you van access enough of them as is. No big deal.

[m2cupcar]

Pulled some wires from a scrap harness so power should come soon. And a graphic:

[m2cupcar]

I need troubleshooting direction/tips. I finally got the the IGN-12v lead soldered on the board, did a flux scrub, hooked up all the grounds and then applied power to all 12v inputs. Immediately LEDs @ INJ1, INJ2, INJ3 went ON/OFF, RPM LEDs went ON and then the CEL LED. I've started examining the injector area of the board with the assumption the issue might be there since the LED at INJ4 did not come on.



full rez photo: http://fe3miata.com/GRM/images/16_0729_JAGA7-back.jpg

video of power applied, LED sequence/action, and then removed: https://youtu.be/aO5Sr5KLgvk

[Fred]

Looks mostly healthy.

1) Not sure why it flashes twice, possibly the way you turn on the power causes it to reset as it comes on?

2) RPM inputs, if held to ground, shouldn't be on, IIRC. Maybe I don't, though. In either case you should be able to touch the wire to ground to make them go off. Given they're pulled up, I'm likely right.

3) I looked over what I could see between CPU and LED and couldn't see anything wrong. One of the LEDs that is working is sitting way up off the board, but the rest looks OK. Some possibilities:

• Input wire could be open/disconnected, or a trace broken/scratched or something
• Input wire could be shorted somewhere (if so, not good! the current limit resistor is at the FET, so the connection before needs to be clean.)
• LED connectivity from FET to 12v feed could be broken.
• LED could be installed backward
• FET could be DOA (dead on arrival)
• CPU pin for this FET could be solder bridged or somehow dry/disconnected.

etc.

Basically trace the subcircuit from CPU pin all the way to the LED stuff, and ensure everyhing looks good. If so, power it up and measure some voltages on different parts. If you put it in SM mode you should be able to control that pin by feeding 5V in through a 1k resistor as the CPU will be in input mode.

Worst case, the CPU has a dead pin, you can just run semi sequential on the car.

If the FET is somehow dead, throw another bridge jumper in, and reroute to the next FET, ignoring this one.

Not sure what else to say.

How's the car itself coming along? Are you going to steal 40th place out from under my lack of Volvo efforts with a Miata? :-D I hope so/not.

[Fred]

On second thoughts, if that firmware is BenchTest you should not get any primes at all.

If it's some car config, then maybe that CPU output is configured as ignition?

What happens if you send it a bench test sequence? An error back saying "I'm not bench test" or lots of flashing lights?

Current link for bench test (will 404 one day): http://builds.freeems.org/firmware/dev/ ... est.s19.gz

[m2cupcar]

INJ1 and INJ5 LEDs were elevated from the board. INJ1 was a bitch and when I finally got it seated it wouldn't work. So I pulled it and got another functioning (tested) LED in it's place. All the INJ LEDs are tested as working.

I installed the ignition jumper at JP1 and 12v that I forgot. Put both RPM inputs to ground and powered up the board. Diode D2 immediately went up in smoke.

I did try to run the benchtest from EMSstudio and it returned the "I'm not benchtest" error.

In hindsight I should have first confirmed the firmware or installed the benchtest fw after powering it up. Then run the benchtest command from EMSstudio. Lesson learned.

I've ordered a new zener diode for D2 from digi-key and hope to receive and install it this week. At that point I should be back at the state where the video was taken on first power-up. I can check the INJ4 LED for action, then attempt to load the benchtest firmware and run that function from EMSstudio.

re: "the car" - The car lacks completion of surge tank and assembly of the fuel system (beer keg, surge tank, external pump) aside from the completion of this A7. Of course that stuff is in Steve's hands since the car is at his shop in Tampa.

[Fred]

No diode should be blowing up here.

If you're saying D2 is a zener, then that's probably across the CPU power supply as a sort of last resort, will be interesting to see if it saved you from a CPU replacement.

I don't understand how, oh, wait. The three holes in a row, you connected the 12v to the middle one, right? If you bridged the outer two that could explain what happened.

But if you did, without current limiting and low input voltage on your supply, quite a bit of stuff may be toast. If you did, not sure what to say, but 3 way jumpers are pretty typically like that, eg HSD/FP/LSD jumper.

Possible casualties (probable if zener went open before you pulled the plug):

• CPU - you know the story here
• Max9926 VR/Hall IC - This one's difficult to fix but also pretty tough
• Comms isolator chip - Easy to test and solder
• MAP/AAP sensors - easy to fix

Less likely to have died:

• Ignition ICs - likely OK
• Regulator - probably OI
• Traces between 12v in, jumper and D2 (please visual these from end to end) - hoping these are OK
• FETs - likely OK
• High side IC - not sure

How quickly did you kill it?

Was the diode still functioning post smoke? Maybe it saved you?

With the jumper checked/fixed and/or removed does it power up OK? Do anything? Can you load firmware to it to test the other ICs?

The fact it was pulsing outputs and responding with that error implies that the fourth channel was likely working fine and that it was just software/config that meant it wasn't behaving "consistently" (consistent with the software, it probably was).

Sorry this happened! Sounds like you have a little time before you're a road block, though.

I demand a picture of that jumper, even if it's privately under NDA :-D