[AudioI] Audio Injector Isolated GPIO Pin Use

[Matt Flax]

For those who come across this thread and can't see the image below, the following pins are routed to the GPIO header on the soundcard's breakout :

 

GPIO : 4, 14, 15, 11

 


 

 
On 29/9/21 11:02 am, Matt Flax via People wrote:
 
 

hi Jonathan,

 

Nice work !

 

The following pins are routed to the GPIO header (mute_logic is a buffered version of GPIO11) :

 
If you want to use some of these pins, you can do it in a few ways. One idea is to short the 40 pin header's pins together. You'll notice the white round circles around these pins on the spare header.
 
Another way to do it is to take them off the GPIO header if you can access it (GPIO11 is not really usable here without the correct alsa mixer settings ).
 

 
 
Matt
 
 

 
 
On 26/9/21 3:31 pm, Jonathan wrote:
 
 
Hi All,
 
 
I did some more investigation. It looks like the UART TX and RX pins on the Audio Injector Isolated are not connected to anything and do not connect to the passthrough header.
 
 
Pin 11 on the Pi header, GPIO17 connects to one input of an AND gate and the output connects to GPIO17 on the GPIO header. The other input of the AND gate connects to a digital isolation IC and to the LMUTE pin of the output header. On the RCA breakout board, LMUTE doesn't seem to be connected to anything, but I'm not sure on that. With black solder mask, the traces are hard to see. If it is floating, a HIGH should make it to that input of the AND gate and a HIGH should make it to the output.
 
 Pin 7 in the Pi header, GPIO4, directly connects to GPIO4 on the GPIO header.
 
 Matt,
 
 
Am I correct with this? I'd like to use GPIO17 and GPIO4 in my application, as well as have the UART TX and RX on the passthrough header. Here is the schematic I drew up:
 

 
 
 
 Thanks.
 

 Jonathan
 
 
 
 On 9/25/21, Jonathan <emuman100 at gmail.com <mailto:emuman100 at gmail.com> > wrote:
 
 > Hello All,
 
 >
 
 > I did some investigation and it looks like one of the GPIO pins that is
 
 > utilized is GPIO17 to trigger the muting relay on the audio output on the
 
 > RCA breakout board.
 
 >
 
 > For my application, I will only be utilizing the audio input, so
 
 > functionality of output muting isn't really needed. The issue is that I
 
 > already utilize GPIO17. I can easily unsolder the GPIO pin header on the
 
 > RCA breakout, but how can I free up GPIO17 in Raspbian then when I enable
 
 > the driver?
 
 >
 
 > Also, are there any other GPIOs that might be utilized on the Audio
 
 > Injector Isolated? I utilize GPIO4, 17, 24, 27, and the console port in my
 
 > application.
 
 >
 
 > Thank you.
 
 >
 
 > Jonathan
 
 >
 
 >
 
 >
 
 >
 
 > On 9/23/21, Jonathan <emuman100 at gmail.com> wrote:
 
 >
 
 >> Hello,
 
 >
 
 >>
 
 >
 
 >> Does the Audio Injector Isolated make use of any GPIO pins on the Pi

 
 >
 
 >> other than the I2C and I2S lines? If so, which ones does it use?

 
 >
 
 >>
 
 >
 
 >> Also, can I simply solder a header to the unpopulated passthrough
 
 >
 
 >> header and have direct access to the GPIO pins? I use a total of 4

 
 >
 
 >> GPIO pins in my project.
 
 >
 
 >>
 
 >
 
 >> Thanks.
 
 >
 
 >>
 
 >
 
 >> Jonathan
 
 >
 
 >>
 
 >
 
 
 

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