jams: Curious in Colorado

jams
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Re: Curious in Colorado

Post by jams » Mon Jan 15, 2018 1:02 am

mrburnette wrote:
Mon Jan 15, 2018 12:26 am
zmemw16 wrote:
Mon Jan 15, 2018 12:06 am
maybe the first few of google with 'controlling emc for older cars' might suggest some other avenues ?
srp
Faraday shielding is perfect if the shield is perfect, but "perfect" does not occur in deployment. I have done some work with an experimental aircraft with a Rotax engine. Faraday shielding and aggressive bypassing has been shown to work adequately.

Google search for best practices...

For the aircraft, I selected the AVR Mega at 5.0 Volts.

Ray
Your experience with the Rotax engine is helpful to know, and the google search link is a better compilation on the issue than I've pulled together in one place. Thanks.

It might be that the non AEC-Q100 rated MCUs and others would perform fine in the auto engine compartment environment with the shielding, but it would be seen as a "weak point" of the design in terms of being a commercial product. If I was doing this for some of my other, non-commercial, work (such as putting instruments on unmanned aircraft for climate research), then I'd certainly look into that option.

Digi-Key still has a supply of a QFN-package version of the AEC-Q100 ATMega328P but they're no longer stocking the TQFP package I'd been using, and the aftermarket parts manufacturer I'm working with doesn't want to get locked into using a microcontroller series that has been discontinued. I modified my board to accept the QFN, and I'm trying to convince them that it would be years (if ever) before they sold enough of the ECUs to use up the existing supply of QFN versions, but they're not buying that argument.

Jim

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mrburnette
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Re: Curious in Colorado

Post by mrburnette » Mon Jan 15, 2018 1:10 am

it seems like the noise isn't affecting the incoming or outgoing signals but instead hammers the ECU directly.
Actually, devices like the thermocouple are differential voltage and the impedance is very, very low. As long as the cold-junction and the transconductance amplifier IC are properly mounted inside the Faraday box, there should be no issues.

Other cabling to senders such as a 910 Ohm water/oil temperature sensor are more critical and need to be well shielded (or twisted pair) and must be properly terminated and high quality bypass capacitors should be utilized. Remember, with these analog senders, a resistor bridge (voltage divider) will provide connection to the analog input which should typically appear to be around 10K to the uC.

dannyf
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Re: Curious in Colorado

Post by dannyf » Mon Jan 15, 2018 5:13 pm

my automotive ECU board.
I think if you take a modern ECU, often made by Renesas, Freescale, Bosch or Infineon, etc., you will find that they are much more powerful than your typical 8-bitter. Obviously, you can have different sorts of ECU boards with different sorts of capabilities but going with a generic 8-bit for an ECU can be challenging.

with that said, you probably want to start a more powerful chip. Among the 8-bitters you mentioned, the AVRs are more powerful than the STM8 and far more powerful thank your typical PICs. So staying with an AVR Arduino isn't a bad choice.

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Re: Curious in Colorado

Post by mrburnette » Mon Jan 15, 2018 7:04 pm

dannyf wrote:
Mon Jan 15, 2018 5:13 pm
<...>
... you will find that they are much more powerful than your typical 8-bitter. Obviously, you can have different sorts of ECU boards with different sorts of capabilities but going with a generic 8-bit for an ECU can be challenging.
<...>
The Op's original intent was stated
I used that 328p in a replacement electronic control unit that I've designed for some older collector-type cars. Unfortunately, I haven't been able to find any other automotive-rated MCU that are 100% compatible with the Arduino IDE.
He really is not creating a modern ECU, rather is working on rather old automotive systems that look nothing like what we have had since say 1996. As such, 5 Volt and 8-bit was working for him. The post came up because the uC he has chosen is no longer available in automotive spec. (one of his requirements.)

So, without rethinking the requirements (which includes the Arduino environment), the Op is struggling to find just the right uC for a replacement without throwing away all of the already written code.

At least that is my understanding of the issues. ... but, I could be off-base on this one.

Ray

jams
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Re: Curious in Colorado

Post by jams » Mon Jan 15, 2018 7:51 pm

So, without rethinking the requirements (which includes the Arduino environment), the Op is struggling to find just the right uC for a replacement without throwing away all of the already written code.

At least that is my understanding of the issues. ... but, I could be off-base on this one.

Ray
Yes, that's exactly right. I do very much appreciate the input and suggestions folks have offered though.

Jim

jams
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Re: Curious in Colorado

Post by jams » Mon Jan 15, 2018 8:05 pm

dannyf wrote:
Mon Jan 15, 2018 5:13 pm
my automotive ECU board.
I think if you take a modern ECU, often made by Renesas, Freescale, Bosch or Infineon, etc., you will find that they are much more powerful than your typical 8-bitter. Obviously, you can have different sorts of ECU boards with different sorts of capabilities but going with a generic 8-bit for an ECU can be challenging.

with that said, you probably want to start a more powerful chip. Among the 8-bitters you mentioned, the AVRs are more powerful than the STM8 and far more powerful thank your typical PICs. So staying with an AVR Arduino isn't a bad choice.
Fortunately, the work that this ECU needs to do is pretty simple - reads a thermocouple input then triggers a couple of switches and sends an output voltage signal. It replaces an old 1970's-technology electronics box that's hard to find. The one in my car failed, so I decided to see if I could make a replacement. I'd been working solely with off-the-shelf Arduino boards (Pro Micro, Mini, etc.) for other projects, but wanted to learn how to design and build custom circuitry, so this seemed like a good project for that.

I've added a couple of bells and whistles such as sending out diagnostics data and internal data logging in eeprom, but the code still fits pretty easily on the ATMega328P. From the STM8A's specs, it looks like it should be able to handle the job but I certainly could be wrong. I'd looked into PICs a bit, but the STM8 seemed better. All that being said though, if I could find a suitable AEC-Q100 rated 32-bit MCU with Arduino support, I'd probably switch to it to avoid getting stuck with an older and perhaps less supported processor.

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Re: Curious in Colorado

Post by mrburnette » Mon Jan 15, 2018 8:45 pm

Just thinking...
There is possibly another solution.
Paul @PJRC.com has spent years working on the competitive Teensy line of boards, most around the NXP/Freescale products. His core code is open sourced as are the libraries and many of his concepts have been retrofitted into the Arduino.cc official line.

You "may" be able to source the ARM chip version of Teensy in AEC-Q100 grade... light research suggests that the MAC5xxxx series is Automotive grade.
Freescale aims to make automotive development easier with the introduction
of the MAC5xxxx 32-bit ARM-based family of MCUs. Leveraging the Kinetis
and i.MX portfolios, our MAC5xxxx automotive MCUs integrate Cortex-A and
Cortex-M cores to deliver the right balance of real-time processing and application
performance. This family of MCUs includes a broad set of documentation,
hardware and software tools, as well as application notes to help speed
development and reduce design costs.

Teensy's core is in my opinion at-least/more compatible that STM32duino and much more than the STM32S core with is just becoming useful.

For example, Paul's Teensy LC is shown here: https://www.pjrc.com/teensy/teensyLC.html#specs
and uses the MKL26Z64VFT4 uC. The trick would be to determine the same instruction set in the MAC5xxxx product category. Likely a Freescale representative could be contacted to validate your research.
PDF Warning ... Freescale Embedded Solutions


Ray

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Re: Curious in Colorado

Post by dannyf » Mon Jan 15, 2018 11:12 pm

From the STM8A's specs, it looks like it should be able to handle the job but I certainly could be wrong.
of the three mcus mentioned earlier, PIC is the least capable (from a processing power perspective), but most resistant to interference, given that it is built on older processes.

if your AVR survived the job, your STM8 should be OK. and if getting the automotive rating is that important to you, STM8A sounds like a nice choice.

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