pimoroni MS51TC0AE Inventor HAT Mini

AI context

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

BOARD: the Inventor HAT Mini is a 65 x 30.5 x 15.5 mm HAT-shaped board for any Raspberry Pi with a 40-pin header, sold fully assembled with the header pins pre-soldered. It stacks four subsystems on one PCB: a Nuvoton MS51TC0AE 8051-class microcontroller with 16-bit PWM and a 12-bit ADC that acts as the HAT's I/O expander, a DRV8833 dual H-bridge for two DC motors, a MAX98357 3.2 W I2S mono amplifier, and eight addressable RGB LEDs. Around them sit four 3-pin servo headers, four 3-pin GPIO headers (all ADC capable, each with its own power and ground), two 6-pin JST-SH motor/encoder connectors, an alternate 2-pin motor socket, a 2-pin Picoblade-compatible speaker connector, a Qw/ST (Qwiic/STEMMA QT) connector, a user button and a pass-through 40-pin header.
MCU POWER AND LEVELS: the MS51TC0AE runs from 2.4 to 5.5 V, and its ADC needs 2.7 to 5.5 V, both as annotated on Pimoroni's own schematic. On the HAT it sits on the Pi's 3.3 V rail, so every expander pin is a 3.3 V logic pin; the I2C bus from the Pi (SDA on GPIO 2 / pad 3, SCL on GPIO 3 / pad 5) and the interrupt line (GPIO 4 / pad 7) are 3.3 V.
PI PADS THE HAT ACTUALLY USES: I2C SDA pad 3, SCL pad 5, I2C interrupt pad 7, UART TX / ultrasonic TRIG pad 8, UART RX / ultrasonic ECHO pad 10, I2S PCM clock pad 12, amp enable pad 22, HAT ID EEPROM ID_SD pad 27 and ID_SC pad 28, LED data pad 32, I2S PCM frame select pad 35, user button pad 37 and I2S PCM data out pad 40. Everything else on the 40-pin header is passed through to the stacking header untouched - which is why Pimoroni can say the HAT 'only uses a handful of pins on your Pi'.
PINOUT: 40 pads on the pass-through header, numbered as the Raspberry Pi numbers them, odd pads one row and even the other, as published on the pinout the vendor links: 1 3V3, 2 5V, 3 GPIO 2 (I2C SDA), 4 5V, 5 GPIO 3 (I2C SCL), 6 GND, 7 GPIO 4 (I2C Int), 8 GPIO 14 (UART TX / TRIG), 9 GND, 10 GPIO 15 (UART RX / ECHO), 11 GPIO 17, 12 GPIO 18 (PCM CLK), 13 GPIO 27, 14 GND, 15 GPIO 22, 16 GPIO 23, 17 3V3, 18 GPIO 24, 19 GPIO 10 (SPI0 MOSI), 20 GND, 21 GPIO 9 (SPI0 MISO), 22 GPIO 25 (Amp Enable), 23 GPIO 11 (SPI0 SCLK), 24 GPIO 8 (SPI0 CE0), 25 GND, 26 GPIO 7 (SPI0 CE1), 27 GPIO 0 (EEPROM SDA), 28 GPIO 1 (EEPROM SCL), 29 GPIO 5, 30 GND, 31 GPIO 6, 32 GPIO 12 (LED Data), 33 GPIO 13 (PWM1), 34 GND, 35 GPIO 19 (PCM FS), 36 GPIO 16, 37 GPIO 26 (User Button), 38 GPIO 20 (PCM DIN), 39 GND, 40 GPIO 21 (PCM DOUT).
REFERENCE CIRCUIT AND VALUES, read from the vendor schematic: motor current limit is set by a 0.47 ohm sense resistor per channel on the DRV8833's AISEN/BISEN pins, and the schematic's own arithmetic is 200 mV divided by 0.47 ohm = 0.425 A, dissipating 0.085 W - so each motor is capped at 425 mA. The MAX98357A runs from 2.5 to 5.5 V and is strapped for gain by R2: not fitted gives 9 dB, 0 ohm gives 6 dB and 100 k gives 3 dB; R1 selects the channel mix: 1 M or 620 k mixes both channels, 0 ohm takes the left channel and 370 k or 220 k the right. Decoupling near the amplifier includes 10 uF 25 V (CL31A106KAHNNNE), 1 uF, 0.01 uF and 1.5 M / 10 k resistors. The eight RGB LEDs hang off a single LED_DATA net from the Pi.
POWER: by default the HAT takes 5 V from the Pi header and feeds the motors and servos from it. An unpopulated screw terminal accepts external power up to 10 A; external 5 V there can power the Pi and everything on the HAT instead of the Pi's USB input. For motors or servos above 5 V the input may be anywhere from 2.7 to 10 V, but only after the trace on the back marked with a lightning bolt is cut.
TRAPS: the addressable RGB LEDs are, in Pimoroni's own words, currently not supported on Raspberry Pi 5. On an unmodified board only one power source may be connected at a time - a second supply back-powers the first. Above 5 V on the motor supply the lightning-bolt trace must be cut first or the Pi is damaged; failing to cut it is the one stated way to destroy the host. The per-motor direction indicator LEDs can be disabled by cutting the traces marked with LED symbols next to the motor connectors. Servo and motor voltage must not exceed 10 V. Motor current is capped at 425 mA per channel by the sense resistors, so a bigger motor will simply stall. The I2C address of the MS51 expander is not published by the vendor, so scan the bus; Pimoroni publishes no pull-up values for the Qw/ST connector either.