The Complete BeagleBone Black GPIO Pinout Table: Every P8/P9 Pin Mapped to Bank, Offset, and Linux GPIO Number

Why I Built This Table

A few posts back I walked through resolving a single header pin (P9_12) to its gpiochip/line number with gpioinfo. That workflow is great when you already know which pin you're chasing. What it doesn't give you is the bird's-eye view — every pin on both 46-pin headers, in one place, so you can pick a free GPIO for a project without flipping between the datasheet, the System Reference Manual, and a terminal. This post is that bird's-eye view.

How to Read This Table

• Header/Pin — the silkscreen label printed on the board (e.g. P9_12).
• GPIO Bank_Offset — the AM335x GPIO bank (0–3) and offset within that bank (0–31), e.g. GPIO1_28.
• Linux GPIO # — the flattened number the classic sysfs interface (/sys/class/gpio) and most tutorials use, computed as bank × 32 + offset.
• Default Function — the pin's most commonly-used alternate (non-GPIO) mux mode on the stock device tree, if it has one.

One caveat worth repeating from the earlier post: gpiochip numbers reported by gpioinfo aren't guaranteed to line up 1:1 with bank numbers — that depends on device tree probe order on your specific kernel. The GPIO bank_offset and the flattened Linux GPIO number below are the stable, hardware-defined values; always confirm the live gpiochip/line with gpioinfo before wiring anything up.

P9 Header (46 pins)

P8 Header (46 pins)

Two Traps Worth Knowing About Before You Wire Anything Up

• P8_27 – P8_46 are usually claimed by HDMI. The stock BeagleBone Black device tree enables the HDMI framebuffer overlay by default, which mux‑locks nearly the entire second half of P8 to LCD data/sync signals. If gpioinfo shows those lines as unavailable or already requested, that's why — you'll need to disable the HDMI overlay (via config-pin or an entry in uEnv.txt) before those pins act as GPIO.
• P8_3 – P8_6 are electrically shared with the onboard eMMC. These four pins carry the same MMC1 data lines used to boot from and access the built-in eMMC storage. On boards booting from eMMC, treat these as reserved unless you specifically know what you're doing.

My Honest Pros & Cons

✅ What I Love

• Every GPIO-capable pin on both headers in one scroll, cross-referenced by bank_offset and the flattened number most tutorials and forum posts actually use.
• Saves the "which pins are actually free" question that comes up at the start of every new BeagleBone Black project.
• Pairs directly with the gpioinfo + pinmux debugfs workflow from earlier in this series when you need to verify a specific pin's live state.

❌ What Could Be Better

• Default alternate functions listed here reflect the stock device tree — a custom device tree overlay can remap any of these pins to something else entirely.
• It's a static reference, not a live query — always double-check with gpioinfo before trusting a number on hardware you didn't set up yourself.

Final Verdict

Bookmark this one. Whether you're picking a free GPIO for a new sensor, double-checking that the pin you want isn't secretly wired to HDMI or the eMMC, or just trying to translate a forum post's "gpio60" into a header label, this table is the fastest path there — faster than re-deriving bank/offset math from the datasheet every time.