aux_bmm150

# Control BMM150 via BMI270 AUX Interface

[中文说明](README_cn.md)

This example demonstrates how to access an external BMM150 magnetometer via the BMI270 AUX interface in manual mode, covering device wake-up, Chip ID verification, operational mode configuration, raw data reading, and clean shutdown. It demonstrates four public APIs:
- `bmi270_aux_set_config()`
- `bmi270_aux_get_config()`
- `bmi270_aux_read()`
- `bmi270_aux_write()`

## Hardware Connection

The communication path is: `ESP32 -> BMI270 (main I2C) -> BMM150 (AUX I2C)`

Default configuration targets the **M5Stack AtomS3R** development board:

| Signal / Parameter | AtomS3R Default | Description |
| --- | --- | --- |
| SDA / SCL | GPIO45 / GPIO0 | ESP32-S3 to BMI270 main I2C bus (400 kHz) |
| BMI270 Address | `0x68` | SDO connected to GND |
| ASDA / ASCL | Onboard link | BMI270 auxiliary I2C bus connected to BMM150 |
| BMM150 AUX Address | `0x10` | Auxiliary slave address |
| ASDA Pull-up | 2 kΩ | Provided by BMI270 internal pull-up configuration |

For other boards, connect the magnetometer to the **ASDA** and **ASCL** pins of the BMI270, ensure common ground and required bus pull-ups, and update the GPIOs and slave address in the configuration.

## Build and Run

1. Navigate to the example directory, set the target chip, and build:
   ```sh
   idf.py set-target esp32s3
   idf.py menuconfig
   idf.py build
   ```
2. Flash and monitor:
   ```sh
   ESPBAUD=921600 idf.py -p PORT flash monitor
   ```

Under **BMI270 AUX BMM150 Example Configuration** in `menuconfig`, you can adjust the pins, slave address, polling interval, and frame count.

## Execution Flow

1. **Bus and Sensor Initialization**: Create the main I2C bus and initialize the BMI270 instance.
2. **Configure AUX Mode**: Disable advanced power-saving, configure the ASDA pull-up, enable AUX manual mode with an 8-byte burst, and verify the settings.
3. **Enable AUX Power**: Call `bmi2_sensor_enable()` to activate the AUX channel.
4. **Wake and Identify BMM150**: Write wake command to register `0x4B`, wait for power-up, then verify Chip ID at `0x40` (expected `0x32`).
5. **Configure Measurement Mode**: Set XY/Z repetition counts and set the operating mode to 10 Hz normal mode.
6. **Periodic Data Acquisition**: Read an 8-byte frame from `0x42`, parse raw X/Y/Z readings and Hall resistance (RHALL).
7. **Clean Teardown**: Upon reaching the frame limit or encountering an error, suspend the BMM150, disable AUX, and delete the sensor instance and bus.

## Output

Successful startup outputs initialization logs followed by CSV formatted data:

```text
AUX manual mode, address=0x10, 8-byte read burst
BMM150 chip ID=0x32
BMM150 normal mode at 10 Hz, XY repetitions=9, Z repetitions=15
timestamp_us,mag_x_raw,mag_y_raw,mag_z_raw,rhall,valid
```

| CSV Field | Description |
| --- | --- |
| `timestamp_us` | Host microsecond timestamp when the frame was read |
| `mag_x_raw`, `mag_y_raw` | Signed 13-bit raw ADC counts |
| `mag_z_raw` | Signed 15-bit raw ADC counts |
| `rhall` | Unsigned 14-bit Hall resistance value (for compensation algorithms) |
| `valid` | Data valid flag; `0` on overflow or zero RHALL, otherwise `1` |

> **Note**: This example outputs raw ADC counts. To convert these readings into microtesla (µT) or compute orientation, apply trim-register compensation (for example, using the official `espressif/bmm150` component).

By default, the example terminates and frees resources after reading 20 frames:
```text
Finished after 20 frames
Sensor and bus released
```
To run continuously, set the frame count (`CONFIG_AUX_BMM150_FRAME_COUNT`) to `0` in `menuconfig`.