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Thread: DIY LTCC or similar system for LT1s

  1. #271
    Fuel Injected!
    Join Date
    Jan 2012
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    Poland
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    I see your point with the DIY-friendly side of Arduino, and probably can agree. You are also right not to make this topic a discussion about pros and cons of different IDEs, so I won't. I just couldn't have helped myself to make that point. :)
    I'll work on your code to move more work on precompiler and clean up the lookups when I'll find some spare time.

  2. #272
    Fuel Injected! spfautsch's Avatar
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    Apr 2015
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    170
    Just so I'm understanding, you're saying you can build precompiler directives that will perform the function of the populate routines so users can edit the following macro definitions / constants and end up with a custom dwell table?

    Code:
    #define DWELL_TGT 4.5       // dwell target in milliseconds - edit to your liking (using 4.5ms for standard ls2 coils)
    #define CRANK_DWELL_TGT 3.2 // dwell target for cranking / startup
    
    #define VOLT_COMP_8 2.4     // adds / subtracts from dwell target at given input voltage
    #define VOLT_COMP_9 1.5
    #define VOLT_COMP_10 0.9
    #define VOLT_COMP_11 0.4
    #define VOLT_COMP_13 -0.2
    #define VOLT_COMP_14 -0.4
    #define VOLT_COMP_15 -0.7
    #define VOLT_COMP_16 -0.9
    #define VOLT_COMP_17 -1.0
    Or are you talking about making the tables statically initialized variables like the RPM table?

    Code:
    int rpmReference[RPM_DIVS] = { 25, 50, 75, 100, 125, 150, 175, 200, // the rpm reference
      400, 600, 800, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, 
      3000, 3200, 3400, 3600, 3800, 4000, 4400, 4800, 5200, 5600, 6000, 6400, 6800 };
    Also, I'm always a proponent of optimizing code but flash and memory resources aren't in short supply at this point.

    Code:
    Sketch uses 9816 bytes (31%) of program storage space. Maximum is 30720 bytes.
    Global variables use 1013 bytes (49%) of dynamic memory, leaving 1035 bytes for local variables. Maximum is 2048 bytes.
    Lastly, I don't see a point in trying to run this on a lesser mcu. This isn't a project focused on profitability, so saving a dollar or two on the mcu only to limit what can be added in the future seems counter productive. One of the reasons I developed a fondness for the adafruit clones is because they developed a bootloader mod that allows no-wait program startup while maintaining the ability to flash the chip over uart hands-off. This is important - I want the user to be able to update the firmware easily in the same way they can tune flash based PCMs. I also want it to be easily customizable, even if that means something as trivial as the end user printing their name or VIN # to uart on startup.

    Latest changes tested and uploaded. Link to github repo is in my signature.

  3. #273
    Fuel Injected! spfautsch's Avatar
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    Apr 2015
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    170
    Partial schematic interfacing to an Arduino compatible device. Sorry for the bunching on the input side, I'm still learning how to use this drawing soft.

    Wire colors on the input side are only confirmed on the Y chassis code. Others may use different colors.

    diy-ltcc-boarduino-1.0-partial.jpg

    The LED + limiting resistor on pin 13 are usually present on all Arduino-like devices so I didn't number them. My ultimate goal is to develop a complete schematic and turn that into a single plane PCB with the Atmega (28 pin dip) directly onboard instead of using the Arduino device as a "daughter board". If that works out maybe we can arrange a group buy for a large quantity.

    I'm hoping it's obvious, but just to be safe the the ancillary output circuitry on pin 4 (coil #1) needs to be duplicated for the other 7 cylinders.

    Edit: R3 and R4 (the famous impedance matching network) is an approximation of potentiometer measurements from this post that produced ~4.29 volts on the EST line's diagnostic ADC channel. Testing and possible fine-tuning may be required (I can't find a 5.6k resistor in my substantial collection of "stuff").


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