Example of Infineon's highly sensitive IM69D130 Microphone Shield2Go board for Arduino.

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The IM69D130 is designed for applications where low self-noise (high SNR), wide dynamic range, low distortions and a high acoustic overload point is required. Infineon's Dual Backplate MEMS technology is based on a miniaturized symmetrical microphone design, similar as utilized in studio condenser microphones, and results in high linearity of the output signal within a dynamic range of 105dB. The microphone distortion does not exceed 1% even at sound pressure levels of 128dBSPL. The flat frequency response ( 28Hz low-frequency roll-off) and tight manufacturing tolerance result in close phase matching of the microphones, which is important for multi-microphone (array) applications. With its low equivalent noise floor of 25dBSPL (SNR 69dB(A)) the microphone is no longer the limiting factor in the audio signal chain and enables higher performance of voice recognition algorithms. The digital microphone ASIC contains an extremely low-noise preamplifier and a high-performance sigma-delta ADC. Different power modes can be selected in order to suit specific current consumption requirements. Each IM69D130 microphone is calibrated with an advanced Infineon calibration algorithm, resulting in small sensitivity tolerances (± 1dB). The phase response is tightly matched (± 2°) between microphones, in order to support beamforming applications.

The IM69D130 Microphone Shield2Go takes the PDM output of the IM69D130 and converts it to I2S using an ADAU7002 IC. The voltage level of the Shield2Go is 3.3 V and it can be directly used with the XMC 2Go as it has the Shield2Go form factor with SPI replaced by I2S.

• Dynamic range of 105dB
  • Signal to noise ratio of 69dB(A) SNR
  • <1% total harmonic distortions up to 128dBSPL
  • Acoustic overload point at 130dBSPL
• Sensitivity (± 1dB) and phase (± 2° @1kHz) matched
• Flat frequency response with low frequency roll off at 28Hz
• Very fast analog to digital conversion speed (6µs latency @1kHz
• Power optimized modes determined by PDM clock frequency
• Package dimensions: 4mm x 3mm x 1.2mm
• PDM output
• Omnidirectional pickup pattern

• Devices with Voice User Interface (VUI)
  • Smart speakers
  • Home automation
  • IOT devices
• Active Noise Cancellation (ANC) headphones and earphones
• High quality audio capturing
  • Conference systems
  • Cameras and camcorders
  • Industrial or home monitoring with audio pattern detection

Please download this repository from GitHub by clicking on Download ZIP at Clone or download dropdown button of this repository or directly here.

Just unzip the file to a location of your choice for further processing the examples. You can also just clone the repository to a location of your choice and work with the repository directly.

Please see the example sketches in the /examples directory:

• sampleReadingWave
• sampleValues
• soundPressureLevel

We will guide you now through using the provided examples with a IM69D130 Microphone Shield2Go in combination with an XMC 2Go.

The IM69D130 Microphone Shield2Go is a standalone break out board with Infineon's Shield2Go formfactor and pin out. You can connect it easily to any microcontroller of your choice which is Arduino compatible and has 3.3 V logic level (please note that the Arduino UNO has 5 V logic level and cannot be used without level shifting).

Please consult the wiki for additional details about the board.

This board uses I2S and will block the SPI ports of the Shield2Go as they are redefined to be compatible with the Shield2Go formfactor.

Overall, the following SPI - I2S pin matching is in place:

• SPI:MISO -- I2S:DATA (INPUT)
• SPI:SCK -- I2S:BCLK
• SPI:SS -- I2S:LRCLK

However, every Shield2Go is directly compatible with Infineon's XMC 2Go and the recommended quick start is to use an XMC 2Go for evaluation. Therefore, please install (if not already done) also the XMC-for-Arduino implementation and choose afterwards XMC1100 XMC2Go from the Tools>Board menu in the Arduino IDE if working with this evaluation board. To use it, please plug the IM69D130 Microphone Shield2Go onto the XMC 2Go as shown below.

Before you can use the examples, ensure that you have installed Arduino as described here. Moreover, the XMC-for-Arduino integration is needed for the XMC 2Go and ensure that you have followed the instructions provided here. Especially, ensure that you integrated the XMC boards into the Arduino IDE and that you have installed the SEGGER J-Link software from the official source. Moreover, ensure that you select the XMC1100 XMC2Go board from the Arduino IDE if you compile the examples.

This example is self-explanatory as it mainly reads out one single microphone and prints the data on the serial monitor. Just follow the instructions provided in the sampleValues.ino file, connect the stacked boards to the PC and press the Upload button. Select the related COM port from Tools – Port and open the serial plotter from Tools - Serial Plotter with the correct COM port and baudrate of 1000000 to see the data. Please note that the serial plotter might get blocked if you flash the example and have selected the wrong baudrate. In this case, just unplug the board immediately with open serial plotter, select the respective baudrate, close the plotter, reattach the board and open the plotter once again.

This example shows how to provide a sound pressure level output for a single microphone. Just follow the instructions provided in the soundPressureLevel.ino file and upload it to the board by pressing the Upload button. Afterwards, please open the serial plotter from Tools - Serial Plotter with the correct COM port and baudrate of 1000000. Now, make some noise and watch how peaks are detected, i.e. you mainly get output when the sound reaches a threshold. Please note that the serial plotter might get blocked if you flash the example and have selected the wrong baudrate. In this case, just unplug the board immediately with open serial plotter, select the respective baudrate, close the plotter, reattach the board and open the plotter once again.

You could easily modify the example and add additional checks or limit the output to a specific range with conditional checks.

This example shows how to stream data via the serial interface for a single microphone and store the output via a Python script as a .wav file. Just follow the instructions provided in the sampleReadingWave.ino file and upload it to the board by pressing the Upload button. Afterwards, please check that you have installed Python 3 as a dependency. If you do not have it installed, you can get it from here and install it. We need the pySerial library, i.e. install it via pip with pip install pySerial if you do not have it.

Now open the file waveSerialSplits.py and add the correct COM port in:

# Global settings of for the serial port
comPort = "COM3"
baudrate = 1000000

If you change the baudrate, this needs to be adapted as well. Please kindly note that COM3 is only an example for a Windows based system and the correct port is dependent on the assignment by your operating system.

Now execute the Python script via python waveSerialSplits.py and if you would like to finish recording, just abort the script.

If you want to change the output file name, just adapt the following line:

# Open a wav file
wavFile=wave.open("output.wav", "w")

Wave file related values, e.g. if you would like to change the sample rate, can be changed here:

# .wav params
nchannels = 1
sampwidth = 4
nframes = 0
sampleRate = 11000

Please be aware that the sample rate is the rate of the actual sampling - if you have overflow or loose values, the actual sampling rate will be lower. This will lead to a wrong playback speed as the actual sampling rate does not match the selected one.

You can now play the recorded file, e.g. output.wav in this case, with Audacity from the example folder.

Sampling rate can be too high to transfer the collected data via the serial interface. The XMC2Go has a maximum baudrate of around 1 MBaud and if the data cannot be transferred accordingly, an overflow will happen. This can be checked in the examples, but currently a maximum sampling rate of 11 kHz for a single microphone is possible with the provided examples.

Please find the datasheet of the IM69D130 here. The product page can be found here.