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Thread: How to avoid noise when writing to the microSD?

  1. #26
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    Quote Originally Posted by defragster View Post
    @MorganS: Is the GPS running off the Teensy 3.3V? On a breadboard? It may be a power draw issue? My T_3.6 could power the GPS, I was not using SD card - but I did pull 3.3v from T_3.6 in two spots to feed the power rail on the breadboard to the GPS. Working on same project somebody else was using external power (with common GND) on the GPS as his similar unit was failing to function - so the power draw may be an issue as the SD does draw some current … as it makes noise.

    @paoloboatto - interesting F_CPU speed change helped - what was the F_CPU when it was failing - 180/216/240/256?
    It was the default 180MHz. To further investigate you can also change the SPI clock speed

  2. #27
    Senior Member+ Frank B's Avatar
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    have you tried to add a decoupling capacitor as near as possible to the sd card? something like 50uF.
    don't know if the placement is good (Paul can answer this), but the 3.6 has 3v3 and GND on the row with VBAT, which is near.
    Edit: perhaps with additional 100nF parallel

    editops sorry, saw this was already proposed above.
    Last edited by Frank B; 04-03-2019 at 11:07 AM.

  3. #28
    Junior Member MorganS's Avatar
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    The CPU speed change does sound like a good idea to try. I expect that the SDIO interface on the onboard SD card is tightly linked to CPU speed.

    I'm powering the GPS from the 5V supply, which is coming from USB for testing. Eventually it will be powered from 12V with a Pololu converter providing 5V to the Teensy and GPS.

  4. #29
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    Quote Originally Posted by MorganS View Post
    I'm powering the GPS from the 5V supply, which is coming from USB for testing. Eventually it will be powered from 12V with a Pololu converter providing 5V to the Teensy and GPS.
    obviously all GND is common, right?

  5. #30
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    Quote Originally Posted by MorganS View Post
    The CPU speed change does sound like a good idea to try. I expect that the SDIO interface on the onboard SD card is tightly linked to CPU speed.

    I'm powering the GPS from the 5V supply, which is coming from USB for testing. Eventually it will be powered from 12V with a Pololu converter providing 5V to the Teensy and GPS.
    It's about 2 years I'm using this solution (change CPU speed) on my board with Teensy 3.6 used as a shield, and it works flawlessy, whatever GPS receiver I'm using

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