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 SKR PICO <-> RASPBERRY PI — UART SETUP
 FOR:      Raspberry Pi 5  ·  Pi 500
 NOT FOR:  Pi 3/4/Zero (own files — their steps DO NOTHING on a Pi 5) · CB1
 P5 POWER VERDICT: NO. The Pi 5 requires a 5 A / 27 W-class supply; the Pico's
                   P5 header tops out at a 3.5 A shared fuse (17.5 W). Power the
                   Pi 5 from ITS OWN USB-C supply and run only TX/RX/GND to P5.
 Source-verified 2026-07-10 against raspberrypi.com official documentation,
 the Raspberry Pi kernel device tree, and BigTreeTech's SKR-Pico repository.
                                                          honeybadger.software
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THE PI 5 IS DIFFERENT — READ THIS FIRST
  * Bluetooth does NOT sit on the GPIO UART here (it has its own dedicated
    UART inside the SoC). The Pi-3/4 overlays (pi3-miniuart-bt, miniuart-bt,
    disable-bt) are USELESS on a Pi 5 — copying BTT's manual recipe adds a
    no-op and misses the one step that matters: enabling uart0.
  * THE /dev/serial0 TRAP: on Pi 5 the serial0 shortcut points at the tiny
    3-pin DEBUG connector (/dev/ttyAMA10), NOT the 40-pin header. Any guide
    that says "use /dev/serial0" silently aims Klipper at the wrong port.
    Always hardcode /dev/ttyAMA0.

STEP 1 — edit /boot/firmware/config.txt — add:
  enable_uart=1
  dtparam=uart0=on

STEP 2 — edit /boot/firmware/cmdline.txt
DELETE the token:  console=serial0,115200

(TUI alternative:  sudo raspi-config -> 3 Interface Options -> I6 Serial Port ->
 login shell NO -> serial hardware YES)

STEP 3 — printer.cfg
  [mcu]
  serial: /dev/ttyAMA0        # NEVER /dev/serial0 on a Pi 5 — see trap above
  restart_method: command

STEP 4 — the wiring (data only on Pi 5!)
  Pico P5:  GND · RX0(IO1) · TX0(IO0)   ->   Pi pins 6 GND · 8 TXD · 10 RXD
  (TX crosses to RX both ways.) DO NOT connect P5's 5 V pins to a Pi 5 —
  it needs its own 27 W USB-C supply.
  Firmware on the Pico: klipper-UART0.uf2 (NOT the USB build).

POWER MATH (why the verdict is NO)
  Official Pi 5 requirement: 5.0 A at 5.1 V (27 W). P5 ceiling: 3.5 A fuse
  x 5 V = 17.5 W, shared with the Pico's own 5 V loads. 3.5 < 5.0 — and GPIO
  back-powering bypasses the Pi 5's USB-C power negotiation entirely.
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