Header	Unit	Interface	Address
`Unit8Encoder.h`	8Encoder - 8 rotary encoders + LEDs	I2C	0x41
`UnitByteButton.h`	ByteButton - 8 buttons + RGB LEDs	I2C	0x47
`UnitJoystick2.h`	Joystick2 - XY joystick + button + LED	I2C	0x63
`UnitScroll.h`	Scroll - single encoder + button + LED	I2C	0x40
`UnitPaHub.h`	PaHub - TCA9548A 6-channel I2C mux	I2C	0x70
`UnitLcd.h`	LCD Unit - 135x240 IPS display (ESP32-PICO)	I2C	0x3E
`UnitDualButton.h`	Dual Button - 2 GPIO buttons	GPIO	-
`UnitCardKB2.h`	CardKB2 - QWERTY keyboard	I2C	0x5F
`UnitMidi.h`	MIDI Unit / Synth Unit - SAM2695 synth	UART	31250 bps
`UnitRfid2.h`	RFID2 - WS1850S/MFRC522-compat RFID reader/writer	I2C	0x28

Usage

Without CMake component

Source files are compiled directly into your app (same pattern as TactilityCpp and SoundEngine). In your app's main/CMakeLists.txt:

file(GLOB_RECURSE SOURCE_FILES
    Source/*.c*
    ../../../Libraries/M5UnitModules/Source/*.c*
)

idf_component_register(
    SRCS ${SOURCE_FILES}
    INCLUDE_DIRS
        ../../../Libraries/TactilityCpp/Include
        ../../../Libraries/M5UnitModules/Include
    REQUIRES TactilitySDK
)

Then include headers as:

#include <UnitByteButton.h>

Standalone (direct I2C)

All I2C units take a Device* from device_find_by_name("i2c1"). External peripherals are on i2c1; i2c0 is reserved for internal device-tree hardware.

#include <tactility/device.h>
#include <UnitByteButton.h>

Device* i2c = device_find_by_name("i2c1");

UnitByteButton bb;
if (bb.begin(i2c)) {
    uint8_t mask = bb.readButtons();  // bitmask, bit i = button i
    bb.setLed(0, 0x00FF00);           // set button 0 LED to green
}

Through PaHub (I2C multiplexer)

When multiple units share the same I2C address, or more than 6 units are needed, connect them via a PaHub. Select the channel before each operation:

#include <UnitPaHub.h>
#include <Unit8Encoder.h>

Device* i2c = device_find_by_name("i2c1");

UnitPaHub hub;
Unit8Encoder enc;

if (hub.begin(i2c)) {
    hub.select(0);       // channel 0
    enc.begin(i2c);      // device on channel 0 is now reachable
}

// In your poll loop:
hub.select(0);
int32_t deltas[8];
uint8_t buttons[8];
enc.readAll(deltas, buttons);

GPIO unit (DualButton)

UnitDualButton uses the Tactility GPIO controller rather than raw ESP-IDF GPIO:

#include <tactility/device.h>
#include <UnitDualButton.h>

Device* gpio = device_find_by_name("gpio0");

UnitDualButton db;
if (db.begin(gpio, GPIO_NUM_36, GPIO_NUM_26)) {
    bool a = db.isButtonAPressed();
    bool b = db.isButtonBPressed();
}

UART unit (MIDI / Synth)

UnitMidi uses the uart_controller kernel driver. Pass a Device* from device_find_by_name() to begin():

#include <tactility/device.h>
#include <UnitMidi.h>

Device* uart = device_find_by_name("uart1");

UnitMidi midi;
if (midi.begin(uart)) {
    midi.programChange(0, 0);      // channel 0, program 0 (Grand Piano)
    midi.noteOn(0, 60, 100);       // middle C, velocity 100
    midi.noteOff(0, 60);
}

CardKB2 in UART mode

After switching the CardKB2 to UART mode (Fn+Sym+2), use beginUart() instead of begin():

#include <tactility/device.h>
#include <UnitCardKB2.h>

Device* uart = device_find_by_name("uart1");

UnitCardKB2 kb;
if (kb.beginUart(uart)) {
    // Poll at ~50ms; returns ASCII of last pressed key, 0 if none
    char c = kb.getKey();
}

The driver tracks Aa (caps lock / one-shot shift), Sym (symbol mode), and Fn internally. Switch back to I2C mode on the keyboard with Fn+Sym+1.

UART mode: Fn+1 (Esc = 0x1B) and Fn+D/X/Z/C (cursor up/down/left/right = 0x1E/0x1F/0x1D/0x1C) are fully supported - the firmware sends the raw KEY_ID in the UART frame and the driver translates it.

I2C mode: Fn+1 and Fn+D/X/Z/C produce no output. The firmware's I2C slave queue only holds regular ASCII; the Fn-combo branch routes directly to BLE HID and does not push to the I2C queue.

BLE HID mode: Standard USB HID keycodes are sent (ESC=0x29, Up=0x52, Down=0x51, Left=0x50, Right=0x4F). The Tactility BluetoothHidHost maps all five to the correct LV_KEY_* values.

I2C protocol note

Most M5Stack Units use an STM32 microcontroller internally. These require a STOP condition between the register-pointer write and the data read (STM32 HAL populates the tx buffer after STOP, before the next START). Using a repeated-START causes bus errors.

UnitCommon.h provides unitReadReg which implements the required STOP + 2ms delay pattern automatically. All STM32-based drivers use this helper.

The LCD Unit is an exception - it contains an ESP32-PICO and uses a command-based I2C protocol without the STOP+delay requirement.

UnitRfid2 - RFID2 Unit

The RFID2 Unit uses a WS1850S chip (drop-in MFRC522 replacement) operating at 13.56 MHz. Read range is under 20 mm.

Supported card types

Card	SAK	Notes
MIFARE Classic Mini	0x09	5 sectors, 20 blocks
MIFARE Classic 1K	0x08	16 sectors, 64 blocks
MIFARE Classic 4K	0x18	40 sectors, 256 blocks
MIFARE Ultralight	0x00	16 user pages
NTAG213	0x00	45 pages; CC byte 0x12 at page 3
NTAG215	0x00	135 pages; CC byte 0x3E at page 3
NTAG216	0x00	231 pages; CC byte 0x6D at page 3

Basic usage

#include <UnitRfid2.h>

Device* i2c = device_find_by_name("i2c1");

UnitRfid2 rfid;
if (rfid.begin(i2c)) {
    UnitRfid2::Uid uid;
    if (rfid.readCard(&uid)) {
        auto type = rfid.getCardType(uid);
        // ...
        rfid.haltCard();
    }
}

readCard() runs the full ISO 14443-3 anticollision/SELECT sequence (including 7-byte and 10-byte cascaded UIDs) and uses WUPA so cards in HALT state are re-detected without needing to be removed.

MIFARE Classic

uint8_t block[16];

// Read with default key (0xFF×6)
rfid.mfReadBlock(4, uid, UnitRfid2::KEY_DEFAULT, block);

// Read trying both Key A and Key B
rfid.mfReadBlockKeyAB(4, uid, UnitRfid2::KEY_DEFAULT, block);

// Read trying all 15 built-in common keys automatically
UnitRfid2::MifareKey keyUsed;
rfid.mfReadBlockAuto(4, uid, block, &keyUsed);

// Write a block
rfid.mfWriteBlock(4, uid, UnitRfid2::KEY_DEFAULT, block);

// Read a full sector (4–16 blocks × 16 bytes; sectors 0-31 = 4 blocks, 32-39 = 16 blocks)
uint8_t sectorBuf[16 * 16];  // max 16 blocks for 4K large sectors
uint8_t blockCount = 0;
rfid.mfReadSector(1, uid, UnitRfid2::KEY_DEFAULT, sectorBuf, &blockCount);

KNOWN_KEYS[15] contains 15 widely-used default keys. mfReadBlockAuto tries each as Key A then Key B, which recovers data from most factory-default or commercially-programmed cards.

Sector trailers (block index % 4 == 3 for sectors 0-31; block index % 16 == 15 for sectors 32-39) contain key and access-condition data; they require the correct key to read and should not be blindly overwritten.

MIFARE Ultralight / NTAG

uint8_t page[4];
rfid.ulReadPage(4, page);    // pages 0-3 are UID/config - skip for user data

uint8_t pages[16];
rfid.ulReadPages(4, 4, pages);  // 4 consecutive pages starting at 4

rfid.ulWritePage(4, page);      // pages 0-3 blocked (pass force=true to override)

Use ultralightPageCount(type) to get the number of user pages for a given NTAG variant. The first user page is always 4.

NDEF write (NTAG)

Write a URI NDEF record starting at page 4. The driver in TestUnitRfid2 handles the full TLV framing, URI abbreviation prefix table (http://, https://, mailto:, tel:, etc.), and page-aligned writes via ulWritePage.

Magic card UID clone (gen1a)

// Clone the UID from `sourceUid` onto a gen1a magic MIFARE Classic card
rfid.mfWriteUid(sourceUid.bytes, targetUid);

mfWriteUid uses the gen1a backdoor sequence (0x40 7-bit frame + 0x43) to open direct write access to block 0, then builds the block with the new UID, computed BCC, and the original SAK/ATQA bytes. Only works on magic gen1a cards - regular MIFARE cards protect block 0 at the chip level.

NTAG21x UID bytes are read-only at the hardware level and cannot be cloned.

M5UnitTest app

Apps/M5UnitTest/ is a hardware test app that provides a live interactive test view for each unit. It auto-detects whether a unit is connected directly or via a PaHub, and scales its UI for both portrait and landscape orientations across all supported screen sizes.

Test view	Unit tested	Notes
`TestUnit8Encoder`	8Encoder	Live delta/button readout; LED colour cycling on encoder press
`TestUnitByteButton`	ByteButton	8 button indicators; tapping a button lights its LED
`TestUnitCardKB2`	CardKB2	Keystroke echo in both I2C and UART modes
`TestUnitDualButton`	Dual Button	Configurable GPIO pin picker; red/blue circle indicators
`TestUnitJoystick2`	Joystick2	XY position bar graphs + button state + LED colour picker
`TestUnitLcd`	LCD Unit	Displays a colour gradient and version info on the unit's screen
`TestUnitMidi`	MIDI / Synth	Channel + program picker; Note On/Off for middle C
`TestUnitPaHub`	PaHub	Per-channel I2C address scanner with periodic re-probe
`TestUnitRfid2`	RFID2	Card detection with UID, type, SAK/ATQA display; Clear to re-scan
`TestUnitScroll`	Scroll	Encoder delta counter + button state + LED colour

The RFID2 test view (TestUnitRfid2) shows a pulsing green circle while waiting, then displays card info on tap. Tapping Clear returns to idle.

README.md Unescape Escape

M5UnitModules

Available drivers