Pi Zero GPIO mapping (Delta/Delta-B)

Legend
3.3V Power
3.5V-5V power
GND
Audio pins
1.3" OLED display connections
Expansion header pins
ESP8266 SDIO pins
ATMega, MCP23017 and GSM connections

Pin Number	Pin name	Function	Used For
1	3V3	3V3	Power for ESP8266/display
2	VSYS	VSYS	VSYS in, VBAT sensing with ATMega
3	GPIO2	SDA	I2C - ATMega, MCP23017, expansion header, testpoints
4	VSYS	VSYS	VSYS in, VSYS sensing with ATMega
5	GPIO3	SCL	I2C - ATMega, MCP23017, expansion header, testpoints
6	GND	GND	Ground
7	GPIO4	GPIO	IR TX
8	GPIO14	RXD	GSM UART TXD
9	GND	GND	Ground
10	GPIO15	TXD	GSM UART RXD
11	GPIO17	GPIO	Expansion header / SPI1 / IR RX
12	GPIO18	GPIO	Expansion Header / I2S / SPI1
13	GPIO27	SD_D3	ESP8266 SDIO pin / ESP-socket GPIO expansion
14	GND	GND	Ground
15	GPIO22	SD_CLK	ESP8266 SDIO pin / ESP-socket GPIO expansion
16	GPIO23	SD_CMD	IESP8266 SDIO pin / ESP-socket GPIO expansion
17	3V3	3V3	Power for ATMega
18	GPIO24	SD_D0	ESP8266 SDIO pin / ESP-socket GPIO expansion
19	GPIO10	SPI_MOSI	Display SPI interface, expansion header
20	GND	GND	Ground
21	GPIO9	SPI_MISO	Expansion header - SPI
22	GPIO25	SD_D1	ESP8266 SDIO pin / ESP-socket GPIO expansion
23	GPIO11	SCK	Display SPI interface, expansion header
24	GPIO8	SPI_CSO	Display SPI interface
25	GND	GND	Ground
26	GPIO7	SPI_CS1	Expansion header - SPI
27	GPIO0	SD_RST	EEPROM SDA / ESP8266 RESET pin / ESP-socket GPIO expansion
28	GPIO1	MCP_INT	EEPROM SCL / MCP23017 interrupt pin
29	GPIO5	DP_RST	Keypad GPIO / Display SPI interface
30	GND	GND	Ground
31	GPIO6	DP_DC	Display SPI interface
32	GPIO12	AUDIO_0	PWM audio
33	GPIO13	AUDIO_1	PWM audio
34	GND	GND	Ground
35	GPIO19	GPIO	Expansion header / I2S / SPI1
36	GPIO16	KEYPAD_INT	ATMega328p interrupt pin
37	GPIO26	SD_D2	ESP8266 SDIO pin / ESP-socket GPIO expansion
38	GPIO20	GPIO	Expansion header / I2S / SPI1
39	GND	GND	Ground
40	GPIO21	GPIO	Expansion header /I2S / SPI1