ESP32 Audio Input Showdown: INMP441 vs SPH0645 MEMS I2S Microphones!

Summary

In this video, the host explores MEMS microphone boards for the ESP32, focusing on the SPH0645 and INMP441. These boards integrate audio amplifiers, ADCs, and I2S interfaces, allowing direct connection without an ADC. The host addresses noise issues from previous setups by implementing advanced filtering techniques. After testing, the INMP441 outperforms the SPH0645 and MAX9814, offering a compliant, noise-free, and DC offset-free signal, despite lacking built-in AGC. The video concludes with a comparison of audio quality and power supply noise resilience, highlighting the INMP441 as the superior choice for audio capture on the ESP32.

Takeaways

• 🎙️ The video discusses options for integrating audio data with the ESP32 using microphone boards.
• 🔍 Previously, MAX4466 and MAX9814 microphone boards with Electret Condenser Microphones were examined, which output an analog signal requiring an ADC for the ESP32.
• 📐 MEMS microphones, like the SPH0645 and INMP441, are introduced, integrating audio amplifier, ADC, and I2S interface, allowing direct connection to the ESP32 without an ADC.
• 🔨 The video creator experienced noise issues on the 3.3V power line from the ESP32 dev board, which were mitigated with an RC filter, an LC filter, and a Low Dropout Voltage regulator.
• 🛠️ A custom PCB was fabricated to test different microphone boards, including headers for the MAX9814 and the two I2S boards.
• 🔄 The I2S interface requires at least three lines: serial clock, word select (LRCLK), and data line, with specific operations for left and right channel data transmission.
• 🚫 An issue with the SPH0645's output not aligning with I2S standards was encountered, but a potential solution was found through forum posts.
• 📡 Interference between I2S signals and the MAX9814 output was noted, leading to separate ADC signal capture for comparison.
• 🌐 The INMP441 board outperformed others, being compliant with standards, producing a good signal without DC offset, and handling noisy power supply well.
• 🔊 The INMP441 board showed less noise compared to the MAX9814, and unlike the MAX9814, it lacks a built-in AGC, requiring software solutions for automatic gain control.
• 🔗 The video concludes with a recommendation to subscribe and a reference to the GitHub repository containing the code used, with a teaser for the next video on audio output from the ESP32.

Q & A

What type of microphones were discussed in the previous video?

In the previous video, Electret Condenser Microphones were discussed, specifically using the MAX4466 and the MAX9814 microphone boards.

How do Electret Condenser Microphones work?

Electret Condenser Microphones work by having a parallel plate capacitor with the distance between the plates varying due to sound waves hitting the diaphragm.

What is the difference between the microphones used in the previous video and the MEMS microphones?

MEMS microphones are constructed using a Micro-Electro-Mechanical System component, whereas Electret microphones are based on a parallel plate capacitor design.

Which two boards with MEMS microphones were examined in the video?

The two boards with MEMS microphones examined were the SPH0645 and the INMP441.

What components are integrated into the SPH0645 and INMP441 boards?

The SPH0645 and INMP441 boards integrate the audio amplifier, ADC (Analog-to-Digital Converter), and the I2S interface.

How does the I2S interface differ from the analog signal output of the MAX4466 and MAX9814?

The I2S interface on the SPH0645 and INMP441 boards allows for digital audio output that can be directly fed into the ESP32 without using an ADC, unlike the analog signal from the MAX4466 and MAX9814 which requires an ADC.

What was the issue encountered when trying to record audio from the SPH0645 board using the I2S interface?

The issue encountered was that data was also coming out on the right channel when it should have only been on the left channel, indicating a timing issue not matching the I2S standards.

What was the solution found to fix the timing issue with the SPH0645 board?

The solution found involved specific settings that were suggested in forum posts to address the timing issues with the SPH0645 board.

How did the video creator attempt to reduce noise from the 3v3 power line in the ESP32 dev board?

The creator used an RC filter followed by a Low Dropout Voltage regulator, and for the follow-up, an LC filter followed by a capacitor multiplier and another LC filter after the LDO regulator.

Which board was determined to be the best performer in the comparison and why?

The INMP441 board was determined to be the best performer because it is standards compliant, produces a good signal with no DC offset, and handles a noisy power supply without any issues.

What is the only downside mentioned for the INMP441 board compared to the others?

The only downside mentioned for the INMP441 is the lack of a built-in AGC (Automatic Gain Control), which would require software implementation for that functionality.