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Thread: Teensy 3.5 vs 3.6

  1. #1

    Teensy 3.5 vs 3.6

    Hi All,

    Just a very quick question. Could I confirm that the Teensy 3.5 actually has 2 more analog pins than the 3.6 does. There are two pins labelled A25 and A26 on the 3.5 but this is labelled usb host header on the 3.6 and the analog pins do not exist.

    The reason I ask is just that my circuit board layout is quite tight and it would be advantageous to me to use A26 on the board. Currently I am using a 3.6 but could use a 3.5. I just wondered if the pins do exist on the 3.6 and are just not labelled on the diagram as the IDE accepts A26 on a T3.6.

  2. #2
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by Steevo25 View Post
    Hi All,

    Just a very quick question. Could I confirm that the Teensy 3.5 actually has 2 more analog pins than the 3.6 does. There are two pins labelled A25 and A26 on the 3.5 but this is labelled usb host header on the 3.6 and the analog pins do not exist.

    The reason I ask is just that my circuit board layout is quite tight and it would be advantageous to me to use A26 on the board. Currently I am using a 3.6 but could use a 3.5. I just wondered if the pins do exist on the 3.6 and are just not labelled on the diagram as the IDE accepts A26 on a T3.6.
    With the Teensy with the USB adapter pointing to the left, on the bottom 5 inner pins (between the outer pins 1-7):

    On the Teensy 3.6, these 5 pins are for the USB host support (a second USB where the Teensy 3.6 is the master, not a client):
    • First pin is 5V for the USB connection;
    • Second pin is D- for the USB connection;
    • Third pin is D+ for the USB connection;
    • Fourth and Fifth pins are ground.


    On the Teensy 3.5, these pins provide A26 and A25 analog input pins:
    • The first pin is not connected;
    • The second pin is A26;
    • The third pin is A25;
    • The fourth and fifth pins are ground (I believe USB has the concept of normal ground and 'earth' ground).


    The same PCB is used for both the 3.6 and 3.5 processors, which means, the 3.5 PCB is not accurate for these 5 pins.

    I assume you are also using A23/A24 (pads underneath the 3.5/3.6) and A10/A11 (through hole pins on the other side of the Teensy (next to pins 21-23).

  3. #3
    Basically, I need an additional analog pin that is not on the standard breadboard layout pins. I cannot use A10/A11 because a track on the circuit board runs along where they are so would be a total pain to re-design it. I don’t want to use any of the pads because the Teensy clips in and clips out as I am using stackable headers on the board so don’t really want to have to solder wires on there. I guess you could solder physical pins to those pads but getting it accurate and strong so it can clip in and out would be difficult.

    That only leaves the A25/A26 pins where there is space on the circuit board and they are physical pins.

  4. #4
    When you say not accurate, do you mean the readings will not be accurate when using those analog pins, or the fact that the pins do not line up exactly with the normal pins.

  5. #5
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by Steevo25 View Post
    When you say not accurate, do you mean the readings will not be accurate when using those analog pins, or the fact that the pins do not line up exactly with the normal pins.
    By not accurate, I mean that the PCB has markings for the 3.6 (i.e. ground, ground, D+, D-, 5v). It does not have markings for the 3.5 (i.e. you just have to know that the 2 pins are A25 and A26, and not D+/D-).

    Note however, that these 5 pins are not lined up so that you could connect to them with a standard 0.1" prototype board. So if you are designing something like a PCB that the 3.5 attaches to, you have to move the connection holes over. The solder pads are lined up in 0.1" (2.54mm) rows, and you could use something like a prototype board that does not join pins together to attach them.

    If you wanted to access those bottom pads (for A23 and A24), you could use this little castlelated board designed by R. Larkin that brings out pins 40-53 to 3 rows on the back (though note, you might loose access to the micro SD card if your solder connections are too high. While I ordered a set, I've never actually used it:


    While it is likely too big for your project, Daniel Gilbert (i.e. Talldog on tindie and loglow here) has two boards that brings out all of the pins from underneath the 3.5/3.6 (his PCB also only mentions the 3.6 pinout):

  6. #6
    Thank you for all of that. Those breakout boards look really useful. They would have been really useful for some other projects I did.

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