Audio Shield Headphone to PC (MacBook) Stereo Mic input

[Davidelvig]

I'd like to connect the headphone output from my teensy audio shield to my Mac for viewing the signals in Audacity.
My macbook pro has the single audio jack, supporting the mixed headphone/mic plug (4 contacts instead of three).
Any guidance on:
- the plug type I should use
- any level/impedance issues I'll have? (note, I grok 'level', but not 'impedance')

When I use my iPhone headphones (with mic), I get audio input on the right channel only, so:
Is there a solution that gets both left and right from the Audio Shield headphone jack to the PC input (to show as stereo input in Audacity)


Thanks

 

[Davidelvig]

OK, never mind...
I plugged in the USB Audio output object, changes the USB Type in Arduino\Tools to Serial + MIDI+Audio, and I get a stereo input on the mac.
Wonderful!
Cheap two-channel oscilloscope!

I do need to put the PROGRAM MODE button on the teensy to upload sketches now.
Arduino 1.6.9
Teensyduino 1.2.9
Do I need an update?

 

[PaulStoffregen]

This will be fixed in 1.31-beta3.

 

[Davidelvig]

Thanks!

Any reason to be afraid of Mac OS Sierra?
I had serial port trouble with the upgrade to El Capitan

Also... and issues going to the latest Arduino ?

 

[PaulStoffregen]

Any reason to be afraid of Mac OS Sierra?

Sierra seems to work fine, as long as you have Arduino 1.6.12. Earlier Arduino versions don't work on Sierra. For 1.6.12, you'll need the latest beta Teensyduino.

So far, no version of Mac OSX has worked well with USB audio. It's a sample rate adapting bug on the Mac side. Details here:

https://github.com/PaulStoffregen/cores/blob/master/teensy3/usb_audio.cpp#L39

https://forum.pjrc.com/threads/34855-Distorted-audio-when-using-USB-input-on-Teensy-3-1

 

[Frank B]

@Paul is there no way to use i2s as trigger for dac/adc (of course, only if i2s is enabled)? perhaps via the LRCLK-pin ?
It would make so many things so much more easy..

 

[PaulStoffregen]

@Paul is there no way to use i2s as trigger for dac/adc (of course, only if i2s is enabled)? perhaps via the LRCLK-pin ?

Could try using pin change interrupts to trigger DMA to the DAC registers, instead of the PDB. Dunno if that'll really work, but seems like it might be possible.

For stereo, you'd need to trigger on both edges, so there could be race condition at startup as to which edge becomes the left and which is the right. Might be other thorny issues I'm not imaging at this moment?