Introduction

Non USB hardware consumes GPIOs on the raspberry pi pin head. Some hardware can be flexibly assigned to different pin (e.g. buttons), but other hardware (e.g. RFID reader, audio DAC) need special functionality, which is only available at certain pins.

This sections only deals with non-USB hardware.

Hardware with fixed pin assignment

This hardware needs certain GPIOs with special functions not available on every GPIO. It is assumed, that rotary encoders and buttons for the same function are not used at the same time.

GPIO	Pin	RFID (SPI)	Audio DAC I2S	Hifiberry MiniAmp	Hifiberry DAC Light, Zero	any HAT
2	3			I2C	I2C	I2C
3	5			I2C	I2C	I2C
8	24	SDA
9	21	MISO
10	19	MOSI
11	23	SCLK
16	36			Mute	free
18	12		BCK	BCK	BCK
19	35		LRCK	LRCK	LRCK
20	38		MCLK Only if DAC has NO own clock!	MCLK	MCLK
21	40		Data	Data	Data
24	18	IRQ other GPIO possible
25	22	RST other GPIO possible
26	37			Shutdown

Hardware with flexible pin assignment

This hardware can be connected to any free GPIO, but it is good practice to align with the standard pin-out of this project.

Classic Pinout

This pinout has compatibility issues with other hardware! I recommend changing the scripts to a new pinout. However, this assignment had been the standard in this project for a while.

GPIO	Pin	Button	Rotary Encoder	other	comment
3	5	Shutdown			fixed GPIO if wake up is required can be used in conjunction with I2C devices
5	29		Volume B (Data)
6	31		Volume A (CLK)		collision with Stop on RFID removal for USB reader
6	31			Stop on RFID removal for USB reader	collision with rotary encoder for volume
13			Mute
16	36	Volume Down
19	35	Volume Up			collision with I2S DAC / Hifiberry
20	38	Previous			collision with some I2S DAC / all Hifiberry
21	40	Play / Pause			collision with I2S DAC / Hifiberry
23	16			Amp Shutdown	PAM8403-Poweroff
26	37	Next		Amp Shutdown	collision with Hifiberry MiniAmp

Flexible Pinout

This pinout is designed to give the least collisions with current and upcoming non-usb hardware by not using any GPIO with additional special functions like SPI (9-11), I2S (18-21), I2C (2,3), UART (14,15), PWM (1: 16,18; 2: 13,19). Please note, that also the special functions overlap (e.g. I2S and PWM).

Suggested GPIOs for playlists are 7, 13-15 and as a second choice PWM and UART GPIOs as they are currently not used in the project.

GPIO	Pin	Button	Rotary Encoder	other	comment
3	5	Shutdown	Switch from Track		fixed GPIO if wake up is required can be used in conjunction with I2C devices
4	7			Stop on RFID removal for USB reader
5	29	Volume up	Volume B (Data)
6	31	Volume Down	Volume A (Clk)
12	32			Status LED
17	11	Mute
22	15	Previous	Track B (Data)
23	16	Next	Track A (Clk)
26	37			Amp Shutdown	usable with Hifiberry MiniAmp and PAM8403-Poweroff
27	13	Play / Pause	Switch from Volume

Numbers in the text are GPIO numbers, NOT the pins.