Audio Adapter Board without Teensy

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jayalfredprufrock

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I recently bought a few of the Audio Adapter boards to have a breakout for the SGTL5000. I'm having trouble talking to it at all and can't seem to even sniff out the I2C address using my bus pirate. I've tried powering it by both 3V and 5V as well as with pull-ups enabled and disabled on the bus pirate. Is there some reason why using the Adapter Board without a Teensy wouldn't work? Any advice would be greatly appreciated. Thanks
 
This definitely falls under the heading of 'any advice' and I'll duck after writing it in case you throw something at the screen:

If your time is worth even a teensy amount of money per hour, wouldn't it make sense to get the Audio Adapter Board working first in its designed configuration so you'd have something to probe, compare against, etc?
 
In retrospect sure, but all I wanted was a breakout for the SGTL5000 and literally that doesn't exist save for a $250 evaluation module. Since I have no experience with the Teensy, I was hoping somebody could simply clarify whether there is a special step or power requirement to use an adapter board without the Teensy itself. Sorry to waste anybody's time.
 
Well, the other possible issue is if you applied 5 volts. That would kill the whole board. It needed 3.3V power.

If you have one that for sure hasn't ever been exposed to 5V, use that one.
 
To get it talking by I2C, you only need to connect 4 wires:

3.3V
SCL
SDA
GND

SDA & SCL have 2.2K pullup resistors to 3.3V, so you don't need to add resistors.

teensy3_audio_pins.png


Edit: The 7 bit I2C address is 0x0A, because the ADDR pin is wired low. Make sure you're talk to address 0x0A.
 
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Thanks for the assistance Paul. I tried 3.3V first without pull-ups and triple-checked my pins with the pinout you've attached. Who knows why it didn't work then, but I subsequently tried 5V so it looks like I might not get to the bottom of this just yet...Regardless, next time I'll just order one with a teensy :) Still, I'm not exactly new to this stuff so I can't imagine why I struggled to get it to work the first time around. Thanks again for your help
 
teensyaudio.JPG

I just noticed the bottom of my board looks a little different than the one shown on your product page. Is this an older revision or something, and if so, did it have any pinout differences? Thanks again for your help.
 
That's the new version. The pinout is identical. You can find both schematics and an explanation of the differences on the web page.

Any audio board that's had 5V applied to the 3.3V pin may be dead. The SGTL5000 chip is rated for 3.6V max. Unpleasant news, but at least not as unpleasant as wasting more time trying to get a damaged board working.

Earlier I said no other connections were needed.... but now that I look at this again, I'm not so sure. It might be unresponsive without a clock applied to the MCLK pin. The Teensy Audio Library turns on that clock early in the I2S object's constructor. I just looked at the SGTL5000 datasheet again, and indeed there's this note at the bottom of page 9:

1. The SGTL5000 has an internal reset that is deasserted 8 SYS_MCLK cycles after all power rails have been brought up. After this time,
communication can start.
Click to expand...

It's been such a long time since I first brought this chip up, and so much work has happened on the DSP stuff in the library since, that I pretty much forgot the chip requires a clock. It probably won't respond at all on the I2C bus without the clock. I'm pretty sure it will talk without BCLK or LRCLK, but I've never tested that. Those clocks are always active whenever Teensy uses the SGTL5000.
 
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This turned out to be exactly the issue. Once I configured a proper MCLK I was able to communicate over I2C without issue. Luckily I didn't fry any boards after all. Thanks for pointing me in the right direction Paul.
 
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