How can i attach a Phat Dac if I have a touchscreen already attached? Pi 3


#1

I haev a new raspberry PI, but I’m bit of a noob and dont want to mess up anything. I’m fine doing software stuff, and can solder - but not quite sure how to fit stuff together so everything still works. I dont have / use a hdmi monitor and want the pi to be portable, so I ideally need both, but can’t find anythgin online to help.


#2

if you are referring to the official touchscreen, then there are no complications as it connects to a dedicated interface. If you are looking at a GPIO solution then how it all fits together will depend on your prefered for factor for the end resukt, there are many options, though possibly dictated by the exact choice of TFT.


#3

I bought the touchscreen from Pimoroni, so I’m sure thats the official one - but I must be missing where the dedicated interface is on the raspberry pi 3. I have the official touchscreen red and black wires attached to the GPIO pins +5v and ground, and correctly working. Where does the PhatDac go - you say it has a dedicated interface. Just to confirm, I have a PI3, GPIO attached official screen as described above, setup as it should be and working. I then have a flat phatdac board and a separate 40 pin thing that came with it. There is no information on what to do with the phatdac and thing it came with… what am i missing? When I have the 5v and ground attached from the touchscreen, theres no space on those pins for the phatdac and connector thing with the screen, and I need the screen! Or does/can the phat dac attach to the raspberry pi 3 in a different way and I’m being super thick?

Just checked, the screen is the 7in touchscreen with the stand from the pimoroni shop.


#4

you do not need to connect anything to the GPIO. Well, you can but you can also supply the screen with power via a dedicated PSU, or a split cable like this one:

… if for some reason you REALLY prefer powering up the touchscreen from the GPIO then you can fit the pHAT DAC with a stacking header:


#5

I think I get it. So, I need a different power supply for the screen other than the one that comes with it (i.e. the black and red wires which must connect to the gpio pins, so i get a separate usb splitter) and then put the PhatDac on the 2x20 gpio pins, yes? You say I don’t need to connect anything to the GPIO - but that’s the only place the phatdac can possibly fit on a pi3, right?


#6

right, yes, I meant you don’t have to connect any part of the screen setup to the GPIO… in fact, I think it’s odd the option is even provided (on the ther hand options are good).

A single 2.5A PSU will be beefy enough to power both the screen and Pi using one of the split cable I posted a link to earlier. In theory the older 2A should be OK too, but it depends what you connect to the USB ports (and GPIO).

You can however power the screen and the Pi using a PSU for each however if you find yourself in overcurrent scenarios too often, but it shoudn’t happen on a 2.5A PSU (even with pHAT DAC fitted) and the usual suspect attached to the USB ports (mouse and keyboard).


#7

Got it - all makes sense, many thanks.


#8

a picture being worth a thousand words, here’s how it all fits together using a splitter: