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Thread: Teensy 3.2/3.5 pin compatibility

  1. #1

    Teensy 3.2/3.5 pin compatibility

    I'm trying to use the Teensy 3.5 pinout & footprint for either the 3.2 or 3.5 on a PC board. I presume (maybe wrongly) that the pin functionality can be programmed the same meaning software written for the 3.2 can use the same pins with the 3.5. I suspect that is why the 3.5/3.6 pins 1 through 28 are reserved in the same order as the 3.2 for upgrading purposes. However, I noticed for example that pins 3 & 4 on the 3.5 can be used for a CAN bus as opposed to the 3.2 with serial Tx & Rx. I wouldn't think that should matter as to usage though. Is that correct?

  2. #2
    Senior Member+ Theremingenieur's Avatar
    Join Date
    Feb 2014
    Colmar, France
    Pin compatibility exists basically and especially for these functions which are traditionally bound to specific pins since the earliest Arduino days. That means that you’ll almost always find at least the same functions on the same pin, when going from a smaller T3.x to a bigger T3.y. Sometimes, the bigger/newer T3 will give additional alternative functions on the same pin.
    Concerning pins 3 and 4, they are CAN0 RX and TX pins on both, the T3.2 and the T3.5. It,s just that the designations on the pin layout cards are slightly different but meaning the same. In case of a doubt, you might always check the respective processor reference manuals where the pin multiplexing is exhaustively listed in chapter 10.

  3. #3
    Thanks much! I just wanted make sure as I have written software for the PJRC Audio Shield and ILI9341 Touch display using the T3.2 and now using it to the T3.5.

  4. #4
    Senior Member+ MichaelMeissner's Avatar
    Join Date
    Nov 2012
    Ayer Massachussetts
    I put together a google document that goes overboard in terms of compatibility:

    Note, there is a sheet with Teensy 4 compatibility stuff, that may not be accurate either with the current beta board or what Paul is proposing will be a more final board.

    Besides the can stuff, some other differences pop out in the first 28 pins:
    • The 3.5 does not have touch support, while the 3.2 does have it;
    • The 3.5 supports single precision floating point in hardware, the 3.2 implements it via software emulation. Both boards will use software emulator for double precision floating point;
    • Pin 2 is a PWM bit in the 3.5;
    • The 3.5 has a second i2c port on pins 3 &4;
    • The location of the back pins is in a different place with the 3.2 and 3.5. The DAC output (digital to analog: A14) on the 3.2 pin has been replaced with a reset pin. On the 3.5 (and 3.6) a pair of DACs was added (A20/A21) in the new set of pins.
    • If you wanted to use the real time clock on the 3.2, you would need to solder in a 32.768 kHz oscillator on the board, while the 3.5 uses a built-in oscillator. In both cases, you would need to connect the Vbat pin to the positive terminal of a 3v coin battery and the ground pin to the negative terminal if you want the system to keep the time when it is powered off.

    Unfortunately, it looks like the forth coming Teensy 4 will have some areas where there is less compatibility. But obviously you will need to wait until it is officially announced (or play along and read the thread about the T4, noting that things can change radically between now and the official product).

    But as Theremingenieur says, for ultimate compatibility, you need to do a deep dive between the two reference documents.

    Quote Originally Posted by jshooks View Post
    Thanks much! I just wanted make sure as I have written software for the PJRC Audio Shield and ILI9341 Touch display using the T3.2 and now using it to the T3.5.
    That should work fine.

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