I am looking for some help

Question

I am newer to DIY electronics and I am working on a project. I have a project that I am building and I am stuck on this one part. I have an Adafruit Mono 2.5W Class D Audio Amplifier - PAM8302 and I want to bring teh Speaker out to another board that will have a Speaker and headphone jack on it. I want to wire it so when the headphones are plugged in the speaker is off and the sound comes through the headphones but when unplugged the sound comes out the speaker. Below is a basic mock up of what I want and I am just stuck on how to accomplish it.

I have tried to Google the answer but have had no luck. Orange dots are the thru hole solder points for each component any help will be appreciated.

genebren · Answer

Jacob, The connections are really quite simple. The diagram below is how it should work. Keep in mind that the pin-out on the headphone jack will need to match the part that you are using. Good luck, Gene

genebren · Answer

Jacob, Not quite sure that I know what you are trying to do here. Best I can tell, Vin and Gnd are your power supply connections (2.5V to 5.5V), SD is used to turn the amp 'on' (Vin) or 'off' (gnd). A+ and A- are your inputs (differential, if single-ended use A+ and tie A- to gnd. How this relates to the USB Test Pads is where I am getting lost. Gene

shabaz · Answer

Hi Jacob, It's not possible in the way you mention, without additional hardware (a USB sound card effectively). Otherwise GPIO can be used. If you don't want to use GPIO connections, then a USB sound card is needed. If you do eventually decide to use GPIO, see here for the circuit you need (in additional to the amplifier which you have already got). https://learn.adafruit.com/introducing-the-raspberry-pi-zero/audio-outputs Or you could connect a digital audio card to the GPIO pins. But it uses GPIO pins.

shabaz · Answer

Hi Jacob, You originally stated that all GPIO pins were in use, is the question now if some are actually free? If so, it is really better if you check (good learning experience). The way to do it is to either find the circuit diagram of this gameboy project if you can, or visually inspect the circuit board if you have purchased it, to see which of the GPIO pins are in use. You could also use a multimeter to probe pins if you really don't wish to find the circuit diagram or if it is not available (if you don't have a multimeter, it is highly recommended). If the GPIO pins are just soldered but really are not going anywhere, then those GPIO pins are free. However, as you can see from the adafruit audio link sent earlier, the audio available on the GPIO pins are on _specific_ pins. You can't interchange. So you'd need to see if those specific pins are free and unused on that gameboy project board. And as mentioned, all you have is an audio amplifier. It can't directly connect to GPIO pins anyway, even if the GPIO pins are free. You need to also assemble the small circuit described on the adafruit page (a total of 4 resistors and 4 capacitors).

ifish · Answer

Hi Jacob,

I think your misinterpreting that table as only GPIO0-27 are available by way of the 40 pin header, its a bit confusing but there are two ways of referencing the pins on the 40 pin header. If you look at the schematic symbol you have posted each pin has a pin number and a description associated to it, pin 40 is in fact GPIO 21.

Which if we look at your table you have linked to isn't capable of being used for PWM

After looking the link you posted I get the feeling the guy used a USB audio device rather then the IO, but if you don't need two sets of triggers you could use GPIO 18 (pin 12) and wire you amplifier to this pin and ground. You'll need to make some software modification, according to Step 7 of the projects setup (https://github.com/32teeth/Gameboy-Zero-Kickstarter/blob/master/INSTALL.md ) you have to edit the control setup anyways. You'll want to free up gpio 18, so delete the following two lines from the config file

A 18 # Left shoulder button

OR

change

A 18 # Left shoulder button

to

A 21 # Left shoulder button

but doing this will require you to lift the tact switch from being connected to GPIO_18 and run a wire from the tact switch to the GPIO_21.

Hope this helps

Chris

I am looking for some help

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