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Thread: Pins Teensy 3/3.1/3.2/3.3/.....

  1. #1
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    Pins Teensy 3/3.1/3.2/3.3/.....

    Not sure which one I have restarting an old project from 2 years ago. Any pin function changed over it's run I should keep in mind? Anyone have issues with slow scl and sda rise times with your audio board attached? I know the pull up should be 100k or so but I had to use 4.7k and even then I remember having to define a slower clock aground 21 khz to get it to connect. I had to rework the wire header file to go

  2. #2
    Senior Member+ MichaelMeissner's Avatar
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    Cool

    The 3.x series has kept the pins the same for the standard pins, but the Teensy 3.5/3.6 added some new features for pins 0..23. By standard pins I mean:
    • Pins for the first 3 serial UARTs RX/TX pins (Serial1=0/1, Serial2=9/10, Serial3=7/8)
    • Pins for the first I2C bus (18/19)
    • Standard pins for the first SPI bus (11, 12, 13)
    • Alternate pins for the first SPI bus (7, 8, 14)
    • Favored CS pins (10, 9, 23/A9, 22/A8, 15/A1)
    • I2S pins for 3.1 and higher (7, 8, 20/A7, 21/A8, 23/A9)
    • Analog input pins (14/A0 through 23/A9)
    • LED is on pin 13
    • Analog ground is between VIN and 3.3v pins
    • Normal ground is next to pin 0
    • The normal ground, analog ground, 3.3v, VIN, and VUSB pins are in the same position


    The Teensy 4.x series has fewer commonalities between the 3.x series and the 4.x series:
    • Serial1 (0/1)
    • First I2C bus (18/A4, 19/A5)
    • First SPI bus (11, 12, 13)
    • Analog input pins (14/A0 through 23/A9)
    • LED is on pin 13
    • The Teensy 4.x do not have an analog ground, but they put a standard ground pin where the analog ground pin in the 3.x series.
    • The normal ground, 3.3v, VIN, and VUSB pins are in the same position


    But a lot of the other pins are different. If you use an audio shield for example, you need to use the revision C shield for the 3.x Teensys and the revision D shield for the 4.x Teensys, as the I2S pins are different, and the 4.x doesn't have alternate SPI pins.


    I put together this spreadsheet to track what each pin does for each of the Teensy models. I also put together a page on the unofficial wiki to describe the commonality:



    In terms of I2C support, you should only need to add resistors if none of the devices on the I2C provides resistors. Typically, 2.2k is an appropriate resistor for 3.3v systems. You can use 4.7k resistors, but the more resistance you add, the slower the I2C bus can become. The Audio shield does provide 2.2k resistors (both revisions C and D). Many newer devices provide resistors also.
    Last edited by MichaelMeissner; 07-21-2021 at 02:33 PM.

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    Thank you! I have to recreate all my code from 2 -3 years ago, I forgot a lot. I got the I2C scanner working to day now I just have to check if the audio board uses address 40 for anything as it showed up in the scan and the documents for the chip I am trying to talk to says it should be on 80. I found an assembly mistake that might have been causing my slow rise times. Maybe I will do better this time!

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    Senior Member+ MichaelMeissner's Avatar
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    FWIW, the audio adapter uses I2C addresses 0x0A/10 (SGTL5000) and 0x1A/26 (WM8731).

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    EDIT: found the headers...

    Thanks again. Do you happen to know where I can find the Audio.h file on windows 10? I searched the drive and it did not find it.
    I have a copy from Paul's github but I would like to know where its located locally.
    Last edited by DaQue; 07-22-2021 at 02:22 AM.

  6. #6
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by DaQue View Post
    EDIT: found the headers...

    Thanks again. Do you happen to know where I can find the Audio.h file on windows 10? I searched the drive and it did not find it.
    I have a copy from Paul's github but I would like to know where its located locally.
    Nope, I only run Linux. Under Linux, if you go to the installation directory, it is in:
    • ./hardware/teensy/avr/libraries/Audio/Audio.h

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    It has the same directory path on Windows.

    Pete

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