PHAT DAC Which GPIO are in use


#1

Just received the Phat DAC and want to combine it with outher stuff on a Pi, Pi0 and Pi2 etc so need to know which pins are in use?

Anyone?


Phat DAC + johnny-five
Explorer + Enviro + DAC Combo
#2

Only the I2S pins and 5V/3V3/GND!


#3

Thank you for the reply. So to be clear, the physical pins 3, 5, 27, 28 + (3v from 1 & not 17, 5v from 2 & 4, & GND from all GND pins

What about Pin 12 (GPIO18)?


#4

GPIO18 is the clock and is used!


#5

Jon, not sure your input has been very helpful.

Got the unit working then started running various other elements inc reading a DHT22 signal on GPIO21 - caused the DAC to crash!

So although I’m not even close to being an expert, but it seems to use GPIO21 (Pin 40) too!


#6

yes! i2s is GPIO18-19-20-21, of which all but GPIO20 are used by the pHAT DAC. I hope this helps… check out pinout.xyz for details, there will be a pinout for this hardware up there soon, but in the meantime you can click on the various pins and see what their purpose(s) are!


#7

on a sidetone physical pins 27 and 28 are not in use, a pHAT is not a HAT ;-)

Edit: I think I see where the confusion lies, you took it as the pHAT using i2c when @jon said i2s?


#8

Here’s one of my minimalist soldering job that should illustrate what pins the pHAT DAC uses (the block at right is not necessary in full only 3 out of 6 pins are):


#9

Thanks RogueM

That’s very helpful for now, I will come back if I trip up!


#10

So, for anyone still not sure, we just need 7 out of the 40 pins.
(right?)

  1. Pin 1 (3.3V)
  2. Pin 2 (5V)
  3. Pin 12 (GPIO 18)
  4. Pin 35 (GPIO 19)
  5. Pin 38 (GPIO 20)
  6. Pin 39 (Ground)
  7. Pin 40 (GPIO 21)

How can I make use of (after pHAT) remaining GPIO pins?
#11

Correct, though you don’t need GPIO 20 (physical 38), technically.


#12

Thanks @RogueM.

So, we need 6 out of the 40 pins.

  1. Pin 1 (3.3V)
  2. Pin 2 (5V)
  3. Pin 12 (GPIO 18)
  4. Pin 35 (GPIO 19)
  5. Pin 39 (Ground)
  6. Pin 40 (GPIO 21)

Help installing Phat Dac
#13

What does need mean here? That GPIO 20 (physical 38) is free to use for other stuff?


#14

Yes. http://pinout.xyz/pinout/phat_dac


#15

I saw the pinout.xyz diagram first, and couldn’t figure out how the pHAT would work without a ground.

Why aren’t pins 1 and 39 marked as used on pinout.xyz?


#16

3v3 is not required. Ground pin would be your choice, all 8 are marked as electrically connected at the pinout site (compare to say, blinkt for an example of ‘strict’ ground mapping).


#17

Hi all this is my first post here so be kind,
This thread seems to be along the lines of what I need. I am currently setting up a Openelec dedicated media player on a Pi 2. It will have a DVD player and a built in harddrive, that will gobble up two USB’s and I want a third for external use, leaving one internal for future expansion. I want to add a simple IR-Reciever, but don’t want the diode to be on the final USB socket. I have previously achieved this successfully on a Pi-zero by hard wiring the IR-diode to the pin GPIO 18. This is the solution I was planning to use this time, but I am also thinking of upgrading the sound with a pHAT DAC. However I have noticed that the DAC uses the same pin as all of the standard tutorials assign to the IR-Remote which points to an incompatibility problem. Can the pHAT DAC use an alternative GPIO pin, or does anyone know if the IR-reciever can use an alternative GPIO pin.

It seems that might be quite a common issue for people building dedicated Squeezeboxes or Kodi boxes.

Hope that all makes sense.

Stephen


#18

It seems that the Lirc Ir module can have its pins allocated to anything within reason: the command is:

Now load the lirc_rpi module (change gpio number is you are using different ones. note that these are gpio numbers, not pin numbers)

sudo modprobe lirc_rpi gpio_in_pin=4 gpio_out_pin=7

This sets pin 4 for IR input to system (physical pin 7)
use Physical Pin 1 for 3v3 power and physical pin 6 for ground.

stephen


#19

pin 18 is mandatory for the pHAT DAC’s operation. I can’t see why IR receiver could not use any standard GPIO, so any other pin should do?


#20

Ok thats what I had gathered by doing a little digging. However the guides for using Lirc-rpi are scant as they all seem to assume you will go with the default pin of GPIO_18.

Stephen