/en/tags/mems/Recent content in MEMS on Mi&Bee BlogHugo -- gohugo.ioen蓝宝石的傻话Mon, 18 May 2026 10:00:00 +0800/en/posts/physical-world/imu-accelerometer-gyroscope/Fri, 15 May 2026 10:00:00 +0800/en/posts/physical-world/imu-accelerometer-gyroscope/<p>Opening post of the Motion Sensing series. Sensors are the window through which embedded systems perceive the physical world, and the IMU (Inertial Measurement Unit) is the most common type. This article skips heavy theory — just how MEMS sensors work, how to wire them, how to read data, and what the numbers actually look like.</p> <h2 id="imu-coordinate-system">IMU Coordinate System</h2> <p>The diagram below defines the three axes of the IMU — all formulas and discussions that follow are based on this coordinate system:</p>/en/posts/physical-world/embedded-anc-stm32/Mon, 18 May 2026 10:00:00 +0800/en/posts/physical-world/embedded-anc-stm32/<h2 id="hardware-architecture">Hardware Architecture</h2> <p>Implementing real-time ANC begins with selecting the right hardware platform. The controller must complete adaptive filtering within microseconds while managing multiple audio data streams.</p> <table> <thead> <tr> <th>Module</th> <th>Function</th> <th>Typical Choice</th> </tr> </thead> <tbody> <tr> <td>Main Controller</td> <td>Executes adaptive algorithm</td> <td>STM32F4/F7, ESP32-S3, nRF5340</td> </tr> <tr> <td>Reference Mic</td> <td>Captures ambient noise</td> <td>Knowles SPH0645, Infineon IM69D130</td> </tr> <tr> <td>Error Mic</td> <td>Captures residual noise</td> <td>Knowles SPH0645, TDK ICS-43434</td> </tr> <tr> <td>Audio DAC</td> <td>Outputs anti-noise signal</td> <td>ES9218, PCM5102</td> </tr> <tr> <td>Amplifier</td> <td>Drives speaker</td> <td>Class-D</td> </tr> </tbody> </table> <p>The reference microphone sits outside the earcup and captures external ambient noise as the algorithm&rsquo;s reference input. The error microphone sits inside the earcup near the speaker, capturing residual noise for evaluating cancellation performance and driving adaptive updates. The audio DAC converts the digital anti-noise signal to analog, which is amplified by a Class-D amplifier to drive the speaker.</p>