[info] Frankenso - ECU shield compatible with OEM case / official

Hardware inside and outside of the ECU
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Re: Frankenso - ECU shield compatible with OEM case

Post by AndreyB »

Or is it a mistake that we do not separate GNDs on the board?

For example http://rusefi.com/wiki/index.php?title=Vehicle:Mazda_Miata_2003 schematics clearly has a separate sensor GND pin 4O (BLK/RED)

Not sure where it's coming from but 3A is designated as "Injector GND" for whatever reason and 3B is PCM GND.
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Re: Frankenso - ECU shield compatible with OEM case

Post by AndreyB »

http://rusefi.com/wiki/index.php?title=Vehicle:Honda_Accord_1995 actually has two signal grounds - one just for MAP, another one for other sensors

A23 and A24 are power grounds while A26 is logic ground. Looks like a there of OEM ECUs using at least three different grounds. Why?
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Re: Frankenso - ECU shield compatible with OEM case

Post by kb1gtt »

On this wiki page, http://rusefi.com/wiki/index.php?title=Manual:Hardware:PCB_design_rules I posted the below.

https://www.maximintegrated.com/en/app-notes/index.mvp/id/5450

The below explains when you want to separate ground and when you do not. Basically if you have high current's which are going to cause the GND voltage to lift, you want to galvanically isolate your power from your analog. Or if you have DC high voltage which won't follow the traces on the signal layer, and the high voltage exceeds the ratings of the analog signals. Frankenso does not have either of those situations. We separated analog and digital signals, in such a way that we don't have cross coupling issues.

Any anyone post articles that talk about why you would separate grounds? I see very few reasons to consider separating grounds, and many articles that are suggest they should be one ground and that you should ground flood your unused areas on the signal planes.
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Re: Frankenso - ECU shield compatible with OEM case

Post by Rhinoman »

russian wrote:http://rusefi.com/wiki/index.php?title=Vehicle:Honda_Accord_1995 actually has two signal grounds - one just for MAP, another one for other sensors
A23 and A24 are power grounds while A26 is logic ground. Looks like a there of OEM ECUs using at least three different grounds. Why?
Externally the wiring is kept separate to avoid high switching currents introducing noise, internally they are often connected to the same ground plane or there are separate sensor and power grounds. Some ECUs also implement a separate ground 'island' for the processor and some a separate power supply for the injectors. There is no one correct solution, each manufacturer has its own preferred method.
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Re: Frankenso - ECU shield compatible with OEM case

Post by kb1gtt »

I don't know the exact circuits you reference, but I do know that some times ASIC's push the limits of cheap, and they can not keep the low frequency currents separate from the analog circuits with out increasing the size and cost of the ASIC. So they instead rely on PCB cuts to steer the low frequency current loops away from the analog circuits.

For me I layout things paying very close attention to the current loops. I've always been able to get the current loops to separate properly such that I don't get analog issues. Any design that has ground plane separations will cause me to raise an eye. For those designs I would like to learn why the designer thinks they need a separation. I would generally expect a design does not need separations.
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Re: Frankenso - ECU shield compatible with OEM case

Post by AndreyB »

Code: Select all

135)                  CANH silkscreen is pointing at the wrong pin, should be moved to the next pin
140)                  D1006 "alt diode for D1004" app note needs to get back to power supply page
141)                  add an app note regarding not having separate injector/analog/else GND on Frankenso
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Re: Frankenso - ECU shield compatible with OEM case

Post by stefanst »

Rhinoman wrote:
russian wrote:http://rusefi.com/wiki/index.php?title=Vehicle:Honda_Accord_1995 actually has two signal grounds - one just for MAP, another one for other sensors
A23 and A24 are power grounds while A26 is logic ground. Looks like a there of OEM ECUs using at least three different grounds. Why?
Externally the wiring is kept separate to avoid high switching currents introducing noise, internally they are often connected to the same ground plane or there are separate sensor and power grounds. Some ECUs also implement a separate ground 'island' for the processor and some a separate power supply for the injectors. There is no one correct solution, each manufacturer has its own preferred method.
To clarify some more:
There's grounds going OUT from the ECU, such as the grounds for the sensors and then there's grounds coming into the ECU.
If all GNDs are connected inside the ECU, then any high current going through the ground-supply for the ECU will pull the ground plane of the ECU up to some degree. So now, when an injector fires for example, we have a ground plane at the ECU which is maybe a few hundred millivolts above ground at the battery.
Example: if the ground supply wiring between battery and ECU has 0.1Ohm resistance and an injector draws 1A, the GND plane of the ECU will be 100mV above GND at the battery. Add to that some current for various valve solenoids, injectors firing simultaneously and you can have several hundred mVs of offset.
This would then mess with the readings of the sensors, if they were connected to ground at a different location, let's say at the cylinder head. In this case the ECU would read sensor voltages that are lower than they actually are, because it's comparing to an artificially high voltage.
Feeding the sensors ground from the ECU through separate wires that don't carry any high current allows their ground to float up with the ECU ground. Signal confusion is thus avoided.
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Re: Frankenso - ECU shield compatible with OEM case

Post by kb1gtt »

If your injector, or any other inductive loads have a 0.1 ohm resistance, you are going to have much larger issues than lifting the GND voltage. Even at 0.01 ohms this resistance will start to cause issues. Your injectors are an inductor separated by a resistor (wire and contacts) which is connected to a capacitor (battery). This general topology is commonly called a tank circuit. Tank circuit resonate which causes surge voltages. AKA 12V on an injector which is clamped with a 40V OVP MOSFET will commonly see 300V to 600V at the injector. However the ECU will only see 12V to 40V.

ECU's commonly have separate GND wires because the designer knew that there are current loops and they know that if they twist the signal and GND wire together any portion of the signal that is above about 1kHz will flow in this twisted GND wire, this controls where the current loop is, and prevents the loop from radiating noise and it prevents the loop from hearing noise.
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Re: Frankenso - ECU shield compatible with OEM case

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96) route unused stm32 pins (PD3 PC13 etc) to unused connector pins
What about clutch switch / brade pedal switch, are we allowed to feed these wires right into stm32 since we can use stm32 own pull-up or pull-down if needed? Firmware-vise I am thinking simply reading the pin state every 20ms.
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Re: Frankenso - ECU shield compatible with OEM case

Post by AndreyB »

Also
143) cars like 2003 miata have separate ignition key +12 and main relay +12. We need to separate +12 trace for flyback D15 etc
routed into a separate pin, with an option for jumper into ignition +12
Also I am planning to split http://rusefi.com/wiki/index.php?title=Manual:Hardware_Frankenso_board page soon - I will focus existing page on end-user manual assuming assembled board and separate assembly-related info into a separate page.
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Re: Frankenso - ECU shield compatible with OEM case

Post by kb1gtt »

Technically yes you can run 5V out and get it to return. The STM should have good enough ESD protection so it should work. However if you cross a 12V wire, then bad things happen. At minimum you would want a series resistor, and a pull down resistor, such that a disconnect is seen as a 0V rail.
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Re: Frankenso - ECU shield compatible with OEM case

Post by kb1gtt »

Why does 12V need to be split from ignition vs main relay? I suspect that 12V ignition is used as part of a security feature. Do we need such a security feature? Can the main relay provide enough current? What pin should 12V ignition be put on?
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Re: Frankenso - ECU shield compatible with OEM case

Post by AndreyB »

Ignition key turns ecu on, ecu turns main relay on, if iac flyback diode on frankenso goes to ignition 12v, ecu turns on and stays on forever since iac flyback is feesing the ecu

In order for ecu to go off we need flyback go not into ignition 12 but into main relay 12
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Re: Frankenso - ECU shield compatible with OEM case

Post by kb1gtt »

I'm still confused. I do not see main 12V going to the ECU, and I see both wires from the IAC go to the ECU. I also do not see how the ECU has any knowledge of if the key is on or off. I'm assuming you have this wired in the Frankenso like this.

Race car has kill switch for mains ECU power, which is not shown on 2003 schematic, the kill switch disconnects "always on" 12V power on pin 4AG.
4AG is wired via jumper to 2P and 2Q is wired to low side driver.
Fly back diode is desired as you want IAC to be sluggish in response. So diode is installed with band side of diode on 2P, and non-band side on 2Q.

I may have 2P and 2Q flipped. I'm not sure how you have this wired.

If it's wired as I noted above, it should not self power the 12V. If it is powering 12V I would suspect that your issue is a bad solder joint or something like that. You could get better protection if your jumper was a diode instead of a wire. This would prevent IAC from being able to back feed the 12V.

I fear that if the 12V mains and 12V ignition are separated on the ECU, then you will be requiring harness changes. If you use the 2 diodes, then I believe this can be used on an OEM harness.
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Re: Frankenso - ECU shield compatible with OEM case

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Re: Frankenso - ECU shield compatible with OEM case

Post by kb1gtt »

Still need more information. Is 2P or 2Q the +12V side? How did you get 12V to which ever one is 12V?
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Re: Frankenso - ECU shield compatible with OEM case

Post by kb1gtt »

Per the voice connection, I understand the 03 miata uses 72 pin connector, interface board and a bunch of jumper wires. Also I see in R0.5, we have JP06 which was likely to accommodate this request. See below graphic to help show where you'll find JP06.
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Re: Frankenso - ECU shield compatible with OEM case

Post by AndreyB »

Yes JP06 is the right idea but why are both pads of this jumper show the same network name? And looks like a trace connects pads? And JP06 is not on the schematics? Could it be that JP06 was more of a place to add wives than a way to break this trace? I think we need to make JP06 a real jumper on the schematics which would be connecting or disconnecting things. Also jumper0805 package so that China would assemble with 0805 0R resistor.

Can we also connect that trace to W32 pad #1 (the lower pad of W32, currently not connected to anything else)

Actually it's
122) need a jumper between W2 and D12-D23 - NB2 miata fly-back should be wired into main relay 12v not ignition on 12v
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Re: Frankenso - ECU shield compatible with OEM case

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See page 15 of schematic, or use ctrl-F to find JP06. This misc stuff is on the top page, bottom left zone E1.

I just changed that to a 0R jumper. It was originally shorted together because at that time it was expected that most applications would want it connected to 12V-bat. I have changed that to be an optional jumper from the now 12V-SNUB to 12V-SWITCHED. Also I added the connection to W32. See repo. Does this work now?
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Re: Frankenso - ECU shield compatible with OEM case

Post by AndreyB »

12v_snub is a success!

Can we make keystone 3557 part number more obvious?

Also D15 location on the schematics is pretty evil. Also need a note along side recent question from @ on why IAC wants diode while injectors do not.
143) move D12-D23 schematics to outputs page, add note mentioning that needed for IAC/VVT but not for injectors
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Re: Frankenso - ECU shield compatible with OEM case

Post by kb1gtt »

I personally do not like the schematic. It's very much drawn by me for me while doing the layout. I don't like the flow from an end user stand point.

KeyStone now reads like this rusEFI_LIB:KeyStone_3557

I changed the note to read like the below. But moving that to the output page is less desirable for me. My goal was that we could change the connector on this page, and could move the diodes to different pins as required. Perhaps that's not a value add theory, but I was trying to keep that section of the PCB replaceable, such that we could get rid of the interface PCB's as qty started to increase.
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Re: Frankenso - ECU shield compatible with OEM case

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@ has pointed out that hi-low schematics and silkscreen and wiki are all totally messed up in terms of numbering
144) HL7 & HL8 silkscreen is missing, HL2 silkscreen position wrong
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Re: Frankenso - ECU shield compatible with OEM case

Post by AndreyB »

I'm sorry I have new ideas.

With all this talk of external true RS232 adapter based on MAX232, can we please have some holes on RX and TX traces? Maybe holes in the relevant BT adapter pads? This case header or wires would be soldered more securely.
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Re: Frankenso - ECU shield compatible with OEM case

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148) route NC located next to PD15 to 3.3V battery+ / RTC mod / see http://rusefi.com/forum/viewtopic.php?f=4&t=460
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Re: Frankenso - ECU shield compatible with OEM case

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Something showed up in the mail?!
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Re: Frankenso - ECU shield compatible with OEM case

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Looks tasty!
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Re: Frankenso - ECU shield compatible with OEM case

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That's a sweet looking Frisbee you have there.
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Re: Frankenso - ECU shield compatible with OEM case

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I'm on vacation to the North Pole ...
I will not return ...
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Re: Frankenso - ECU shield compatible with OEM case

Post by mzk »

Rev. 0.5

Not red though. There is INJ-12 track (bottom layer) routed right under the upper right (edge cut) side.
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Re: Frankenso - ECU shield compatible with OEM case

Post by AndreyB »

A screenshot of kicad showing the problem and why exactly is the concurn could be helpful?
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