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Thread: Teensy2 power consumption

  1. #1

    Teensy2 power consumption

    Hello all-

    I'm attempting to baseline the power usage of my setup before I start monkeying with sleeping and disabling stuff, and I'm getting really odd results. I'm using a T2 at 3v3 with the MCP supply from PJRC. I recently got a microUSB breakout board from Sparkfun, so now I'm feeding everything through that and using a cut miniUSB cable to talk to the T2.

    I have breakouts from Adafruit for their 128x32 OLED and their Ultimate GPS attached that I've measured before with my craptacular Horrible Freight DMM. I remeasured them today and they're at the expected values: the display ~3-5mA, gps ~25mA.

    But when I finally put my DMM on the T2, I got ~85mA?!

    I'm stumped, and I've probably done something really stupid. Can any of you Teensy experts see anything wrong with my setup? I've attached a photo of the breadboarding.

    Thanks,
    Z

    P.S. I had to create a new account to post this since the forum server doesn't appear to be sending out reset emails, perhaps the mailserver needs a swift kick in the ass?

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  2. #2
    Screwing around with this more, with the microUSB power removed, if I connect my DMM across the cut red miniUSB wire (i.e. the T2 is now being powered through its own miniUSB connection), I get 10mA, which is much better!

    For a data only USB cable, should I cut the ground in the cable as well? Is that what I'm seeing?

    Thanks,
    Z

  3. #3
    Senior Member PaulStoffregen's Avatar
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    Have you measured just the current to the OLED module?

    OLED looks awesome, but it doesn't have a very good reputation for low power usage.

  4. #4
    Sorry Paul, the email notifications aren't working for me, so I missed your reply.

    I too was baffled, so I disconnected everything from the T2 and loaded your power sketch. I was able to replicate your findings, and it turns out that in my sketch, even though I'd disabled the UART explicitly, it wasn't getting shutdown, so I had to toss in a "Serial.end()", which wasn't obvious to me at the time.

    Thank you for the feedback, I appreciate it!
    Z

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