FPGA in ECU

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kb1gtt
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Re: FPGA in ECU

Post by kb1gtt » Sun Jan 12, 2020 10:22 pm

We are currently doing a bunch of clock cycles in the STM32 to decode the crank wheel and update the timer(s). Would we get less watts from the STM32 if that is not done by an STM32? Or are those clock cycles still consuming energy just not producing results? I think the watts are simply transferred from the STM32 to the FPGA. I guess build and test is the only real way to know if the total watts balance has gone up, down or stay the same. It sounds like we do not expect an increase that would warrant additional thermal management needs.

About SMPS, I was thinking we are currently commonly using a chip which includes CAN, VR interface, AEQ friendly power supply, and a bunch of features like that. The MicroSemi chip has many of those features, but I did not see the power supply. I wonder if it's practical to put in some logic to allow for a regulator. Could we some how put in some logic to allow the FPGA to function as the SMPS, or is that not practical? AKA can we create something that will actually boot, then increase the efficiency with a SMPS once the FPGA has been loaded.
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Rhinoman
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Re: FPGA in ECU

Post by Rhinoman » Mon Jan 13, 2020 1:07 pm

The STM will still consume the same power if the processing is done by the core unless you put it to sleep the programme counter will still be running and stepping through addresses. The power consumed by the FPGA will depend on how much logic is actually switching. For an engine timer you would usually have one high resolution timer and a bunch of input capture/output compare modules. The GTM is a good example of a configurable engine timer, but its complex and it would probabl;y be easier to port the RusEFI code to a processor with a GTM.
I think part of the issue here is the perceived lack of accuracy. I haven't looked at the rusEFI code for a long time but if I remember correctly it uses the input capture/output compare modules to trigger interrupts and the clock capture and pin toggling is performed manually in the interrupt. No OEM ECU runs that way, but maybe there is an issue in synchronising the timers that prevents a conventional IC/OC method.

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