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Thread: Question about minimal required pin hookups between Teensy 4.0 and audio adapter

  1. #1
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    Question about minimal required pin hookups between Teensy 4.0 and audio adapter

    Hey guys, I'm working on an audio project with a bunch of inputs and just wanted to make sure my research was correct on which pins I'll need to connect to make this function. I don't need to use the SD card or anything, I just need to use the output audio jack to play sounds generated from Audio Library code.

    From this thread:

    https://forum.pjrc.com/threads/57167...-0-I2S-Support

    I assumed that I'd only need to hook up the following pins: 23(MCLK1), 21(BCLK1), 20(LRCLK1), 7(OUT1A), 8(IN1). Will connecting these suffice in playing basic synthesized sounds from the T4's running code through the audio jack of the Audio Adapter?

    Sorry for my bombardment of super noob posts on this forum, but I do hope one day to be a contributing member of this community! You guys are all so great and helpful.

    Thanks!

  2. #2
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by bigtony View Post
    Hey guys, I'm working on an audio project with a bunch of inputs and just wanted to make sure my research was correct on which pins I'll need to connect to make this function. I don't need to use the SD card or anything, I just need to use the output audio jack to play sounds generated from Audio Library code.

    From this thread:

    https://forum.pjrc.com/threads/57167...-0-I2S-Support

    I assumed that I'd only need to hook up the following pins: 23(MCLK1), 21(BCLK1), 20(LRCLK1), 7(OUT1A), 8(IN1). Will connecting these suffice in playing basic synthesized sounds from the T4's running code through the audio jack of the Audio Adapter?

    Sorry for my bombardment of super noob posts on this forum, but I do hope one day to be a contributing member of this community! You guys are all so great and helpful.

    Thanks!
    No, you need a few more:
    • Ground pin between VIN and 3.3v. While there are two ground pins, previous discussion has mentioned that this ground pin is needed for the adapter to process sound. If you were using the SD drive, you would need to hook up the other ground pin (next to pin 0). This is due to the designs of the previous Audio Adapters for the Teensy 3.x processors;
    • 3.3v pin next to that;
    • Pin 19 (SCL0). You need to use I2C (pins 19 and 18) to control the SGTL5000;
    • Pin 18 (SDA0);
    • Pin 15 -- you don't need to connect this pin unless you want to connect a potentiometer to the 3 pins on the adapter for volume or other purposes.
    • Pins 13, 12, 11, 10, 6, and ground next to pin 0 -- since you don't plan to use the SD card or to solder flash memory onto the board, you don't need to connect these pins.

  3. #3
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    Quote Originally Posted by MichaelMeissner View Post
    No, you need a few more:
    • I don't think you need to hook up the VIN pin;
    • Ground pin between VIN and 3.3v. While there are two ground pins, previous discussion has mentioned that this ground pin is needed for the adapter to process sound. If you were using the SD drive, you would need to hook up the other ground pin (next to pin 0). This is due to the designs of the previous Audio Adapters for the Teensy 3.x processors;
    • 3.3v pin next to that;
    • 19 (SCL0). You need to use I2C (pins 19 and 18) to control the SGTL5000;
    • 18 (SDA0);
    • 15 -- you don't need to connect this pin unless you want to connect a potentiometer to the 3 pins on the adapter for volume or other purposes.
    • 13, 12, 11, 10, 6, and ground next to pin 0 -- since you don't plan to use the SD card or to solder flash memory onto the board, you don't need to connect these pins.
    Thanks for the help. So along with 23,21,20,8, and 7 I'll also need GND(between 3.3 and Vin), 3.3V, 18, 19. Awesome, thanks.

  4. #4
    Senior Member+ defragster's Avatar
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    This page pjrc.com/store/teensy3_audio.html has good summary detail. The GND pin by pin 0 is essential to complete the circuit thingies. The AGND is also connected.

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    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by defragster View Post
    This page pjrc.com/store/teensy3_audio.html has good summary detail. The GND pin by pin 0 is essential to complete the circuit thingies. The AGND is also connected.
    Yeah, it is probably a good idea to connect both ground pins. I thought there was a recent post by somebody asking why the SD card didn't work if you only connected the ground pin between VIN and 3.3v. IIRC, he said it worked fine for the audio stuff.

    In the Teensy 3.x where the two ground pins are different, you need to connect the digital ground pin next to pin 0 to the SD/flash SPI ports and to connect the analog ground pin between VIN/3.3v to the audio stuff. I would imagine when Paul designed the revision D board, he didn't bother changing that.

  6. #6
    Senior Member+ defragster's Avatar
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    Quote Originally Posted by MichaelMeissner View Post
    Yeah, it is probably a good idea to connect both ground pins. I thought there was a recent post by somebody asking why the SD card didn't work if you only connected the ground pin between VIN and 3.3v. IIRC, he said it worked fine for the audio stuff.

    In the Teensy 3.x where the two ground pins are different, you need to connect the digital ground pin next to pin 0 to the SD/flash SPI ports and to connect the analog ground pin between VIN/3.3v to the audio stuff. I would imagine when Paul designed the revision D board, he didn't bother changing that.
    Yeah - that PJRC page with schematics shows they both have some connection - and looking at the PCB's in hand shows them to be wired off. Not having the right GND indeed nixes SD usage - and the 3.3V without GND is just potential for trouble abusing other pins to make a circuit.

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