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Thread: Teensy 3.2 not receiving RX data

  1. #26
    Senior Member Wozzy's Avatar
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    FYI,

    This tiny SD6128 Stepper motor controller can control stepper motors up to 36V and 2.2A with up to 128 microsteps and it works perfectly with a 3.3v input signal.

  2. #27
    Senior Member PaulStoffregen's Avatar
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    Many times before we've seen lengthy threads where someone wouldn't show us photos or real info. Then when a picture finally did get posted, the problem turned out to be something "easy" like a missing ground wire or those breadboards where the power rails are split in the middle.

    No matter how compatible some other device may be, these sorts of "simple" problems come up all the time. Everyone does it. I do it. The difference for experts is we have lots of tools and experience for troubleshooting, and with that experience comes intuition that something which isn't immediately working is most likely just not connected correctly. Without that sort of experience, many people just assume the thing which didn't immediately work must be defective or broken or incompatible, and those assumptions mentally block them from effectively troubleshooting or learning.

    That's why it's so critically important to say exactly what is really being connected, and to show photos or real info about how the wires are really connected.

  3. #28
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    Quote Originally Posted by PaulStoffregen View Post
    If the stepper driver looks like this:...

    Yes, that is the diagram I used to connect the driver. I have 5v to opto, ENA is disconnected. I was not using pinmode input, only output with digital write high and low. This worked fine with the Uno modules. I can see that the 3.3v was not enought to turn the current to the opto coupler.

    Thanks again

  4. #29
    Senior Member PaulStoffregen's Avatar
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    I'm skeptical the problem is merely 3.3V vs 5V signals. Virtually all optocouplers have IR LEDs, so the diode forward voltage is approx 1.25 volts. That diagram shows a 270 ohm resistor. So with 5V you'd get 13.6 mA into the LED. With 3.3V you'd get 7.6 mA.

    Almost all optocouplers work with 7.6 mA into their LED. Yes, it's theoretically possible those particular optocouplers need somewhere between 7.3 to 13.6 mA to work properly, but I believe that is a very unlikely explanation for why this didn't work.

    Something simply not connected properly, or mistakes in the code (or both) are a far more likely scenario.

  5. #30
    Senior Member Wozzy's Avatar
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    artistinfla,

    I just noticed that your code indicates using pins 21, 22, and 23 for the motor control signals.
    Your schematic sketch shows the stepper motor controller hooked up to pins 7, 8, and 9.
    If this is how it's actually hooked up this would definitely cause a problem.

    Could you post a photo of your actual setup?

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