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Thread: CS42448 with Teensy 4.0 vs Teensy 3.2 Pin Compatibility

  1. #1

    CS42448 with Teensy 4.0 vs Teensy 3.2 Pin Compatibility

    Hi, I am working on an audio project using teensy that needs several channels of high fidelity i/o. In the past I've used the Teensy 3.2/3.6 with the CS42448 codec, having reverse engineered the following example board to include the relevant sections on my own PCBs: https://oshpark.com/shared_projects/2Yj6rFaW

    For this project I'd like to use the 4.0 because of its increased processing power. When looking up whether the 4.0 is compatible with the CS42448 codec, I saw that there is a new example board for the 4.0 series: https://hackaday.io/project/2984-tee...-for-teensy-4x.

    Unfortunately these pages don't appear to include schematic information, so at first glance its hard to tell whether anything meaningful has changed for my application. I wanted to ask whether the pinout of codec connections has changed, or whether the 4.0 is pin for pin compatible with the older codec board. Figured it would be more expedient to ask those that had designed the board than to rehash the process of reverse engineering, only to find they were exactly the same.

  2. #2
    Senior Member+ MichaelMeissner's Avatar
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    The I2S pins in Teensy 4.x completely changed compared to the Teensy 3.2.

    In addition on the Teensy 3.2 two of the SPI pins needed to be relocated. On the Teensy 4.x, you use the standard SPI pins.

    I posted this reply about pin differences comparing the Teensy 3.x to Teensy 4.x in terms of the audio shield:

  3. #3
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    Also, there is no need for reverse engineering, the printed cards, the teensy schematic, and the audio shield schematic on the website show the I2S pins.. not sure what you're doing...

  4. #4
    Quote Originally Posted by Frank B View Post
    Also, there is no need for reverse engineering, the printed cards, the teensy schematic, and the audio shield schematic on the website show the I2S pins.. not sure what you're doing...
    This codec uses TDM, not I2S. Not as well documented.

  5. #5
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    Aren't that the same pins? (did not check that now.. )

  6. #6
    Quote Originally Posted by MichaelMeissner View Post
    The I2S pins in Teensy 4.x completely changed compared to the Teensy 3.2.

    In addition on the Teensy 3.2 two of the SPI pins needed to be relocated. On the Teensy 4.x, you use the standard SPI pins.

    I posted this reply about pin differences comparing the Teensy 3.x to Teensy 4.x in terms of the audio shield:
    This post is not about the audio shield. It is about a specific TDM based codec board. Please see the links I included.

  7. #7
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    From the Audio GUI help (another source..)
    TDM:
    Hardware

    TDM has been tested with this CS42448 Board for Teensy 3.x and this CS42448 Board for Teensy 4.x and this ADAU1966A Board for Teensy 4.x.

    T3.x
    Pin
    T4.x
    Pin
    Signal Direction
    9 21 BCLK Output, 11.3 MHz
    11 23 MCLK Output, 22.6 MHz
    22 7 TX Output, 11.3 Mbit/sec
    23 20 WS Output
    Audio from master mode TDM may be used in the same project as ADC, DAC and PWM signals, because all remain in sync to Teensy's timing

    Examples
    I2S:

    The I2S signals are used in "master" mode, where Teensy creates all 3 clock signals and controls all data timing.
    T3.x
    Pin
    T4.x
    Pin
    Signal Direction
    9 21 BCLK Output
    11 23 MCLK Output
    22 7 TX Output
    23 20 LRCLK Output
    The differences must be pretty well hidden

    Edit: The difference is in the timing and number of bits. They both use the inbuilt I2S hardware. So, the pins are identical (as shown above). The main difference is just software.
    Edit: You can take a look at the sourcecode, too (again easier than reverse engeneering boards) - its inside the audo library folder.
    Last edited by Frank B; 08-23-2021 at 01:58 PM.

  8. #8
    Senior Member houtson's Avatar
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    @grinch - there is also a schematic of the Teensy 4 board here put there by another user along with kicad files, it may be useful.
    cheers, Paul

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