jessikitty
c21f804812
Keeps the shared-rail version documented as the alternative, since that is what the current loom attempts, and links the new pinout reference.
3.2 KiB
Wiring
Pin availability and limits: ESP32-PINOUT.md.
Board to board
| Board A (esp32_bluepad32) | Board B (esp32 2.0.17) | |
|---|---|---|
| GPIO17 TX | → | GPIO16 RX |
| GPIO16 RX | ← | GPIO17 TX |
| GND | — | GND |
| 5V | — | 5V (model setup only, see README) |
TX goes to RX, not TX to TX. The ground is a shared voltage reference so the two boards agree on what a logic 1 is — without it you get garbage or silence. It is not a return path for anything else, so do not hang LED current off it.
LED circuits — recommended build
Each LED gets its own wire out and its own wire back to its own GND pin. Four wires, no shared junction anywhere.
GPIO25 ──[220Ω]──▶|── RED pair ──── GND (a)
GPIO26 ──[100Ω]──▶|── GREEN pair ── GND (b)
GND (a) and GND (b) are different physical pins but the same net inside the board. That is fine, and it is exactly what makes this safe: there is no shared connection point to wire incorrectly.
Both circuits live entirely on board B. LED long leg (anode) faces the resistor and GPIO side. A reversed LED simply stays dark, so it looks like a dead circuit rather than a wiring error.
Resistor values are a starting point: roughly 220Ω for red, 100Ω for blue or white. A pin is comfortable at about 12mA and hard-limited near 40mA. If a pair draws more than ~20mA — which pre-wired "3V" LEDs sized for a coin cell often do — drive it through a small NPN transistor or MOSFET instead of off the pin.
Shared ground rail — the other way
Also valid, one wire fewer, but it has a junction that can be wired wrong:
GPIO25 ──[220Ω]──▶|── RED pair ────┐
├── ground rail ── board B GND
GPIO26 ──[100Ω]──▶|── GREEN pair ──┘
The two returns must meet only at the ground rail, and the rail goes straight to a GND pin. See the failure mode below for what happens when that junction lands in the wrong place.
Known failure mode: LEDs wired in series
Symptom seen on this build — green only lights when red is already on, and green never lights alone:
| Software state | Observed |
|---|---|
| red on, green off | red on ✓ |
| red off, green on | both off ✗ |
| red on, green on | both on ✓ |
| red off, green off | both off ✓ |
Cause: the green return lands on the anode side of the red LED rather than on the ground rail, putting the two LEDs in series. Green alone then has to push through both — roughly 2.1V plus 1.9V — and a 3.3V pin cannot do it, so neither lights. With GPIO25 also high, the junction is lifted and both conduct.
Two rows of that table are impossible from a software fault, which is what identifies it as wiring.
Test: with both LEDs off, meter from the shared return wire to a GND pin. It must read 0V. Press Circle and measure again — if it rises above 0V, that wire is not ground.
Fix: switch to the separate-ground build above. It removes the junction entirely, so this cannot recur.
Created by: Jess Rogerson (yelling commands at Claude.AI)