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BeagleBone Black P9 Header

The power, serial, I2C, SPI and analog side of the BeagleBone Black. The seven ADC channels take 1.8 V at most.

Cheat sheet (SVG)

Logic level: 3.3 V / 1.8 V ADC
Package: 2x23 2.54 mm (P9)

1.Pinout diagram

Highlight a signalhover to preview, click to keep

Odd pins

BBB P9

Even pins

Pin detail

Hover a pin for its mappings and gotchas. Click to keep it here.

Logic level: 3.3 V / 1.8 V ADC
Package: 2x23 2.54 mm (P9)

Fig. 1. BeagleBone Black P9 Header, 2x23 2.54 mm (P9). Hover or tap a signal to light up every pin that carries it.

2.Watch out

AIN0 to AIN6 are 1.8 V maximum, not 3.3 V. Putting 3.3 V on an analog pin destroys the ADC, and it is the single most common way to kill a BeagleBone. Divide every input down.
VADC (pin 32) is the 1.8 V reference and AGND (pin 34) is the analog return. Use those, not a digital GND.
VDD_5V (pins 5 and 6) is only live when the barrel jack is connected. SYS_5V (pins 7 and 8) is the regulated rail and works on USB power too, so capes should take 5 V from there.
I2C2 on pins 19 and 20 is the cape EEPROM bus and already has pull-ups. You can hang other devices on it, but address 0x54 to 0x57 are reserved for cape EEPROMs.
Pins 41 and 42 are each wired to two processor balls. Whichever one you are not using must be set to input, or the two fight each other.
Signal names here are the power-on defaults. Almost every pin can be muxed to something else through the device tree, which is both the strength and the learning curve of this board.
GPIO are 3.3 V and not 5 V tolerant. Source or sink 4 to 6 mA per pin, far less than a Pi.
The other side of this board is the P8 header, documented separately: gwark.dev/openlabbench/pinouts/beaglebone-black-p8

3.Full pin reference

Every pin, alias and mapping. This is the table that prints.

Table 1. Pin assignments.

Complete pin reference for BeagleBone Black P9 Header
Pin	Name	Also called	Functions	Notes
1	GND	-	Ground
2	GND	-	Ground
3	DC_3.3V3.3 V	-	3.3 V rail	250 mA budget across both 3.3 V pins.
4	DC_3.3V3.3 V	-	3.3 V rail
5	VDD_5V5 V	-	Barrel jack 5 V	Only live when the barrel jack is plugged in, not on USB power. 1 A for capes.
6	VDD_5V5 V	-	Barrel jack 5 V
7	SYS_5V5 V	-	Regulated system 5 V	Present on USB power too. This is the one to use for a cape.
8	SYS_5V5 V	-	Regulated system 5 V
9	PWR_BUT	-	Power button	Pull low to request a soft shutdown.
10	SYS_RESETn	A10	Reset, active low
11	UART4_RXDUART	T17, GPIO0_30	UART4 RXD
12	GPIO1_28	U18	GPIO1_28
13	UART4_TXDUART	U17, GPIO0_31	UART4 TXD
14	EHRPWM1APWM	U14, GPIO1_18	eHRPWM1A
15	GPIO1_16	R13	GPIO1_16
16	EHRPWM1BPWM	T14, GPIO1_19	eHRPWM1B
17	I2C1_SCLI²C	A16, GPIO0_5	I2C1 SCL
18	I2C1_SDAI²C	B16, GPIO0_4	I2C1 SDA
19	I2C2_SCLI²C	D17, GPIO0_13	I2C2 SCL	I2C2 is the cape EEPROM bus and already has pull-ups fitted.
20	I2C2_SDAI²C	D18, GPIO0_12	I2C2 SDA	Cape EEPROM bus, pull-ups already fitted.
21	UART2_TXDUARTSPI	B17, GPIO0_3	UART2 TXD, SPI0 D0
22	UART2_RXDUARTSPI	A17, GPIO0_2	UART2 RXD, SPI0 SCLK
23	GPIO1_17	V14	GPIO1_17
24	UART1_TXDUART	D15, GPIO0_15	UART1 TXD
25	GPIO3_21	A14	GPIO3_21
26	UART1_RXDUART	D16, GPIO0_14	UART1 RXD
27	GPIO3_19	C13	GPIO3_19
28	SPI1_CS0SPI	C12, GPIO3_17	SPI1 CS0
29	SPI1_D0SPI	B13, GPIO3_15	SPI1 D0
30	SPI1_D1SPI	D12, GPIO3_16	SPI1 D1
31	SPI1_SCLKSPIClock	A13, GPIO3_14	SPI1 SCLK
32	VADC1.8 V	-	ADC reference	1.8 V reference for the analog inputs. Not a rail to power things from.
33	AIN4ADC	C8	ADC channel 4	Analog in, 1.8 V MAX. 3.3 V here destroys the ADC. Scale every input.
34	AGND	-	Analog ground	Return for the ADC. Keep analog returns off the digital GND pins.
35	AIN6ADC	A8	ADC channel 6	Analog in, 1.8 V MAX. 3.3 V here destroys the ADC. Scale every input.
36	AIN5ADC	B8	ADC channel 5	Analog in, 1.8 V MAX. 3.3 V here destroys the ADC. Scale every input.
37	AIN2ADC	B7	ADC channel 2	Analog in, 1.8 V MAX. 3.3 V here destroys the ADC. Scale every input.
38	AIN3ADC	A7	ADC channel 3	Analog in, 1.8 V MAX. 3.3 V here destroys the ADC. Scale every input.
39	AIN0ADC	B6	ADC channel 0	Analog in, 1.8 V MAX. 3.3 V here destroys the ADC. Scale every input.
40	AIN1ADC	C7	ADC channel 1	Analog in, 1.8 V MAX. 3.3 V here destroys the ADC. Scale every input.
41	CLKOUT2Clock	D14, GPIO3_20, D13	CLKOUT2, GPIO3_20	Shared between two processor balls, D14 and D13. Set whichever one you are not using to input.
42	GPIO0_7PWMSPI	C18, GPIO3_18, B12	GPIO0_7, eCAP0 PWM, SPI1 CS1	Shared between two processor balls, C18 and B12. Set the unused one to input.
43	GND	-	Ground
44	GND	-	Ground
45	GND	-	Ground
46	GND	-	Ground

Primary sources

Found a wrong pin? The whole board is one file, data/boards/beaglebone-black-p9.json.

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