pimoroni RP2350B Pico LiPo 2

AI context

Dense context for pasting into a model prompt — addresses, pinout, voltages, tolerances and the vendor's reference circuit.

PART: Pimoroni Pico LiPo 2, order code PIM775, a 51 x 21 mm (about 53 x 21 x 10 mm including connectors) Raspberry Pi Pico-shaped board built on the RP2350B - dual Arm Cortex-M33 cores at up to 150 MHz, 520 kB SRAM, 48 usable GPIO, 8 ADC channels and 24 PWM channels, with an optional RISC-V Hazard3 core pair instead of the M33s. Around it Pimoroni fits 16 MB of QSPI flash (Winbond W25Q128JVPIQ, XiP capable), 8 MB of PSRAM (AP64x04L-class APS6404L-3SQR-ZR, chip select can be GP0, GP8, GP19 or GP47), an MCP73831 single-cell LiPo charger set for 215 mA, an XB6096I2S battery protector, a 3.3 V regulator rated 600 mA, USB-C, a Qw/ST (Qwiic/STEMMA QT) I2C socket, an 8-pin SP/CE socket, a 3-pin JST-SH debug socket, an on/off power button, and a BOOT button that doubles as a user switch.
ADDRESSES: none. Nothing on the board answers I2C, so a bus scan finds only what you attach to the Qw/ST socket.
PINOUT: 40 pads on 2.54 mm headers, printed GPIO numbers only (no pad numbers). Numbering here is the Raspberry Pi Pico convention: 1-20 down the left edge from the USB-C end, 40-21 down the right edge, so pad 1 (GP0) and pad 40 (VBUS) sit at the same end. 1=0, 2=1, 3=GND, 4=2, 5=3, 6=4, 7=5, 8=GND, 9=6, 10=7, 11=8, 12=9, 13=GND, 14=10, 15=11, 16=12, 17=13, 18=GND, 19=14, 20=15, 21=16, 22=17, 23=GND, 24=18, 25=19, 26=20, 27=21, 28=GND, 29=22, 30=RUN, 31=26/A0, 32=27/A1, 33=GND, 34=28/A2, 35=ADC_VREF, 36=3V3, 37=3V3 EN, 38=GND, 39=VSYS, 40=VBUS. That is 26 GPIO, eight GND pads, and the six power/reset pads. Four GPIO are not on the header: GP25 drives the user LED, GP45 is the BOOT/user button (active low, so it reads low when pressed), GP24 is the VBUS sense and GP43 is the battery sense (VBAT through a 1M5/750k divider). The Qw/ST socket is on I2C0 with SDA on GP4 and SCL on GP5; the SP/CE socket exposes eight pins printed VSYS, 3V3, CS, SCK, TX, RX, BL, GND, and its SPI/serial lines are the RP2350B's GP32-GP36.
SUPPLY: USB-C input rated 3 V to 5.5 V; a 3.7 V single-cell LiPo or Li-Ion pack on the 2-pole JST-PH socket (polarity is printed on the board) runs the same rail, so the board works from USB, from the cell, or from both. The on-board 3.3 V regulator is rated 600 mA maximum output. 3V3 EN is driven by the board's power latch, not left free.
LOGIC LEVEL: 3.3 V throughout. The RP2350B's I/O is not 5 V tolerant - a 5 V source on a GPIO needs level shifting.
ANALOGUE: the three analogue pads are printed 26/A0, 27/A1 and 28/A2, but the ADC channels behind them are the RP2350B's ADC0, ADC1 and ADC2 on GPIO40, GPIO41 and GPIO42, reached through three 1 kOhm elements of the RN2 resistor array. A designer must count that 1 kOhm as source impedance; anything expecting a direct bond to the ADC pin is wrong. 26/A0, 27/A1 and 28/A2 also sit directly on GP26, GP27 and GP28 as digital pins.
REFERENCE CIRCUIT: the charger is an MCP73831T-2ACI/OT with a 4k7 PROG resistor (215 mA), a 10 uF input capacitor, a 4k7 on its status LED, and a 100 nF on VDD. Battery protection is the XB6096I2S (52 mOhm on resistance) in series with a DMP2075UFDB pair (64 mOhm each), about 180 mOhm total, i.e. a 180 mV drop at 1 A. The power button drives a 74LVC1G74 latch whose SET path is slowed by R24 (100 kOhm) and a capacitor so the chip reliably powers up on; a 4k7 pull-up and a 2.2 uF sit on that network. The battery sense divider is 1M5 over 750k. USB has R25 100 kOhm on the VBUS detect and 27 Ohm-class series parts on D+/D-. Pimoroni's schematic shows no pull-up resistors on the Qw/ST SDA and SCL nets, so an I2C add-on has to bring its own.
TRAPS: (1) Pimoroni states the RP2350 on current stock is the A2 stepping, which is affected by the RP2350-E9 erratum - if the design pulls an input low, external pull-downs of 8.2 kOhm or smaller may be needed. (2) The power LED can be disabled by cutting the trace marked with a LED symbol on the rear near the USB-C end, which is the only way to get the lowest sleep current. (3) Above 800 mA of draw the battery protector must be bypassed by soldering the trace marked '+1A Mode', and only if the cell can deliver that current. (4) The board must only be used with LiPo/Li-Ion packs - no other chemistry is supported by the MCP73831 setting. (5) Headers, battery and cables are not included. (6) GP24, GP25, GP43 and GP45 are used on-board and are not on the header, so code written for a Pico 2 that toggles GP25 for the LED works, but code that expects those pins on the header does not.