ACT_LED
System
Chip Pad: GPIO16
Green OK/ACT status LED wired to GPIO16 (active low)
Powered by the 700 MHz Broadcom BCM2835 ARM1176JZF-S processor with VideoCore IV graphics and 512 MB PoP LPDDR2 RAM, the Raspberry Pi 1 established both the classic 26-pin P1 GPIO header (Model B Rev 2) and the modern 40-pin J8 HAT standard (Model B+). The header breaks out 3.3V CMOS GPIOs multiplexed across SPI0, SPI1, I2C1, PL011/mini-UART, hardware PWM, PCM/I2S audio, and GPCLK outputs. Model B+ upgrades the 3.3V linear LDO (50 mA budget on Rev 2) to a high-efficiency buck converter, adds 4x USB 2.0 ports, MicroSD, and 4 HAT mounting holes. All GPIO pins are strictly 3.3V-only (never 5V tolerant), with fixed 1.8 kOhm pull-ups on GPIO2 and GPIO3.
Onboard Peripherals & Internal Signals
P5_AUX_HEADER
PIO
Chip Pad: GPIO28
Unpopulated 8-pin P5 header exposing +5V, +3.3V, GPIO28..31 (I2C0 / PCM I2S), and GND
P6_RESET
System
2-pin unpopulated reset header near HDMI (short to reset BCM2835)
Pin Assignment Planner
Add the peripherals you need and plan the pin assignments
Full Pin Reference (26 Pins)
| Pin # | Label | Type | Functions | Warnings & Notes |
|---|---|---|---|---|
| 1 | 3V3 | power | 3V3_OUT |
[CAUTION] 50 mA max total 3.3V load (linear LDO regulator)
All Raspberry Pi GPIO pins operate at 3.3V CMOS levels. Never connect 5V logic directly to any GPIO pin.
|
| 2 | 5V | power | 5V_RAIL |
[DANGER] Direct 5V supply rail — NEVER wire to 3.3V GPIO pins without level shifting
Connected directly to the 5V input power bus.
|
| 3 | GPIO2 | digital | GPIO2 I2C1_SDA DPI_VSYNC |
[CAUTION] Fixed 1.8 kOhm onboard pull-up resistor to 3.3V
Hardwired 1.8 kOhm physical pull-up to the 3.3V rail for I2C1; cannot be disabled in software.
BCM GPIO2 / I2C1_SDA (was GPIO0 on early 256MB Model B Rev 1).
|
| 4 | 5V | power | 5V_RAIL | |
| 5 | GPIO3 | digital | GPIO3 I2C1_SCL DPI_HSYNC |
[CAUTION] Fixed 1.8 kOhm onboard pull-up resistor to 3.3V
Hardwired 1.8 kOhm physical pull-up to the 3.3V rail for I2C1; cannot be disabled in software.
BCM GPIO3 / I2C1_SCL (was GPIO1 on early 256MB Model B Rev 1).
|
| 6 | GND | ground | GND | |
| 7 | GPIO4 | digital | GPIO4 GPCLK0 DPI_D0 ARM_TDI |
BCM GPIO4 (Bank 0, reset default: pull-up HIGH; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 8 | GPIO14 | digital | GPIO14 UART0_TXD UART1_TXD DPI_D10 |
[INFO] Default Linux serial console pin (disable serial console in raspi-config to use freely)
Enabled by default as the boot/login serial console unless disabled via raspi-config or cmdline.txt.
BCM GPIO14 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 9 | GND | ground | GND | |
| 10 | GPIO15 | digital | GPIO15 UART0_RXD UART1_RXD DPI_D11 |
[INFO] Default Linux serial console pin (disable serial console in raspi-config to use freely)
Enabled by default as the boot/login serial console unless disabled via raspi-config or cmdline.txt.
BCM GPIO15 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 11 | GPIO17 | digital | GPIO17 SPI1_CE1_N UART0_RTS UART1_RTS DPI_D13 |
BCM GPIO17 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 12 | GPIO18 | digital | GPIO18 PCM_CLK PWM0_0 SPI1_CE0_N DPI_D14 |
BCM GPIO18 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 13 | GPIO27 | digital | GPIO27 SD0_DAT3 SD1_DAT3 ARM_TMS DPI_D23 |
BCM GPIO27 (was GPIO21 on early 256MB Model B Rev 1).
|
| 14 | GND | ground | GND | |
| 15 | GPIO22 | digital | GPIO22 SD0_CLK SD1_CLK ARM_TRST DPI_D18 |
BCM GPIO22 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 16 | GPIO23 | digital | GPIO23 SD0_CMD SD1_CMD ARM_RTCK DPI_D19 |
BCM GPIO23 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 17 | 3V3 | power | 3V3_OUT | |
| 18 | GPIO24 | digital | GPIO24 SD0_DAT0 SD1_DAT0 ARM_TDO DPI_D20 |
BCM GPIO24 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 19 | GPIO10 | digital | GPIO10 SPI0_MOSI DPI_D6 |
BCM GPIO10 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 20 | GND | ground | GND | |
| 21 | GPIO9 | digital | GPIO9 SPI0_MISO DPI_D5 |
BCM GPIO9 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 22 | GPIO25 | digital | GPIO25 SD0_DAT1 SD1_DAT1 ARM_TCK DPI_D21 |
BCM GPIO25 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 23 | GPIO11 | digital | GPIO11 SPI0_SCLK DPI_D7 |
BCM GPIO11 (Bank 0, reset default: pull-down LOW; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 24 | GPIO8 | digital | GPIO8 SPI0_CE0_N DPI_D4 |
BCM GPIO8 (Bank 0, reset default: pull-up HIGH; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|
| 25 | GND | ground | GND | |
| 26 | GPIO7 | digital | GPIO7 SPI0_CE1_N DPI_D3 |
BCM GPIO7 (Bank 0, reset default: pull-up HIGH; strictly 3.3V/1.8V CMOS, NOT 5V tolerant).
|