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Postby Ken76 » Sun Sep 10, 2017 9:13 pm

Cheers guys,

I'm quite new to the raspberry scene and still learning but I am planning to install a Raspberry Pi zero wireless together with a 2.8 capasitive touchscreen(adafruit) and a Justboom amp zero hat in a "pimp my radio-project". I need some qualified advice from someone who knows what they are doing so to speak.
Would this be a problem when stacking these units with regard to the GPIO-pins?
Would it be possible to back power the screen from the Justboom amp (which already back powers the RPi) or should I use a separate power for the screen?


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Postby Dave » Mon Sep 11, 2017 10:50 am

Hmm, this might not work...

The Adafruit touch screen - ... uchscreen/ - Uses:

I2C (GPIO02/Pin 3 and GPIO03/Pin 5)
SPI (GIPO10/Pin 19, GPIO09/Pin 21, GPIO11/Pin 23 and GPIO08/Pin 24)
GPIO24/Pin 18
GPIO25/Pin 22

And the JustBOOM amp uses these pins -

As you can see GPIO24 is required by both boards. This is used to control the volume on the AMP, but I'm not sure what it's used for on the screen.

They also share the I2C pins, which shouldn't be a problem as long as they have different hardware addresses.


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Postby Ken76 » Wed Sep 13, 2017 9:18 am

Hi Dave!

Thank you for responding and sorry for my late reply.

I read that the I2C pins could be used by several boards but how can I be sure of this? (except from testing that is)

The GPIO24 represents a problem... I do want to use the rotary encoder. Is it possible to rearrange the pins for this in the SW? (I'm planning to use Max2play for my setup) This would probably give me some unwanted problems when upgrading the SW I guess...?

Do you have any recommendations for a similar small setup? I can fit a 2.8" and possible 3.5" touchscreen and it would be nice if it was capacitive.



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Postby BMS Doug » Thu Sep 14, 2017 12:55 pm

It looks like the Adafruit touchscreen uses GPIO 24 as the interrupt pin for the touchscreen controller.

It looks like all of the Waveshare touchscreens use GPIO 24 as well,

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Postby Ken76 » Fri Sep 15, 2017 8:38 am


Thank you for giving me some insight. It seems like I have to find another solution, then... That's a pity since it would be a sweet setup for my Tivoli radios. In fact it would be a terrific solution for most rebuilds/modifications to smaller equipment that doesn't have the space for a larger touchscreen that uses the dsi Interface. Someone, a bit more knowledgeable than me and preferably the makers, should look into this and come up with a good idea.


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