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First please abandon this JUNK hardware!!!!!!!!!!

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  • #16
    The SOM takes the place of the phone to run the java. A cortex M0 daughter micro would run the motors and servos.

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    • #17
      Arm Cortec M0 is a core, it doesn't define a suitable technology for this purpose. Most microcontrollers that use this core are unsuitable for this application for a couple reasons, one being that few implement a real PWM peripheral that is good for motor control, the other is that most have really crappy compilers that generate unreliable opcode.

      The exception is Microchip variants using this core. They make the best microcontrollers for this type of application, IMHO. (low-cost motor control) I tried a ton of different families of products, and was appalled how bad the compilers are for almost all of them. (they generate code that compiles, but the timing is all over the place.) For example, a loop in one branch of code might execute in 2 uS, in a separate branch the same loop takes 3 uS. This will never be noticed if you are designing a controller for a washing machine, but kills the ability to use it when you are bit-banging a 250K waveform while taking multiple polls to filter noise.

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      • #18
        Originally posted by 11343_Mentor View Post
        Arm Cortec M0 is a core, it doesn't define a suitable technology for this purpose. Most microcontrollers that use this core are unsuitable for this application for a couple reasons, one being that few implement a real PWM peripheral that is good for motor control, the other is that most have really crappy compilers that generate unreliable opcode.

        The exception is Microchip variants using this core. They make the best microcontrollers for this type of application, IMHO. (low-cost motor control) I tried a ton of different families of products, and was appalled how bad the compilers are for almost all of them. (they generate code that compiles, but the timing is all over the place.) For example, a loop in one branch of code might execute in 2 uS, in a separate branch the same loop takes 3 uS. This will never be noticed if you are designing a controller for a washing machine, but kills the ability to use it when you are bit-banging a 250K waveform while taking multiple polls to filter noise.
        To clarify the above statement, I wanted to emphasize that when I said that I tried out a ton of different families of products, I meant to say by other companies, not by Microchip. The Microchip compilers are outstanding, they generate very compact, reliable, repeatable code.

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        • #19
          Originally posted by 11343_Mentor View Post
          ... I am having trouble understanding why virtually every discussion about PID motor control forgets about acceleration, because I have never seen it implemented, and it is clear that REV didn't implement it in the Run Using Encoder functions.

          This also applies to sensing. The legal sensors for FTC have a great amount of noise and variability, like most sensors without some built in smoothing or integration function. What I would love to do is to take multiple sequential samples, throw out the outliers, then average them for the best result. This doesn't work in the current environment as the loop time can be anywhere from a few milliseconds to hundreds of milliseconds. This would a trivial function for a basic microcontroller.
          Acceleration & deceleration is implemented in the Roboteq controllers, as well as torque modes and mixed modes. Also, Roboteq loop time is 1 ms or less.

          I suggest we continue this discussion in the thread that ejschuh has created in the Coaches and Mentors sub-forum. Students are most welcome to join the discussion.

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          • #20
            This too is my 4th year of struggling with phone issues. I volunteered to be a coach so that I could mentor youth in the design/engineering process. I have spent the bulk of my time as coach staring into black boxes wondering what random offerings of resets and power-ups will appease the gods. I empathize with ejschuh concerning the time suck this has become. I don't mind taking time away from my family and personal life to be with kids, but not to dive down de-bugging rabbit holes.

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