CompactSix

A six channel compact microphone array based on the Beaglebone Black and the STA321MP audio processor.

Bill of Materials

The full BOM is in file pcb/CompactSix_BOM.txt but here is a list for minimal functionnalities.

For the BBB cape with the Audio Processor:

• 1x STA321MP Audio processor (Mouser 511-STA321MPLTR)
• 1x 12.288MHz oscillator (Mouser 732-SG210STF12.288S3)
• 1x Micromatch Female-On-Board SMD 10 pin connector (Mouser 571-8-2178711-0)
• 3x 0 Ohm Resistor, 0805 package
• 2x 100 Ohm resistors, 0805 package
• 5x 10K Ohm resistors, 0805 package
• 1x 1uF capacitors, 0805 package
• 8x 100nF capacitors, 0805 package
• 1x 10nF capacitors, 0805 package
• 1x 1nF capacitors, 0805 package
• 1x 10pF capacitors, 0805 package
• 2x pin headers 2x40, 2.54mm spaced

Currently, we do not need the audio amplifier at all so that part can be left out. To add the RTC and the temperature sensor, add the following:

• 1x Temperature sensor TMP275 (Mouser 595-TMP275AIDR)
• 1x RTC DS1338 (Mouser 700-DS1338Z-33T&R)
• 1x CR2032 Battery holder (Mouser 712-BAT-HLD-001)
• 1x 32.768 kHz crystal (Mouser 815-ABS07-32.768KHZT)
• 2x 100nF capacitor
• 1x 10K Ohm resistor

For the six small microphone boards:

• 6x SPM1437HM4H-B PDM MEMS Microphones (Mouser 721-SPM1437HM4H-B)
• 6x 100nF capacitors, 0805 package

For the cable:

• 1x Micromatch Male-On-Wire 10 pin connector (Mouser 571-12150830)
• 30cm flat cable, 1.27mm, 10 wires

Hardware Configuration

There are three options that can be configured using resistors.

1. XTI source The master clock for the STA321MP audio processor can be supplied either from the a crystal oscillator or from the McASP module from the BBB. The configuration is marked as XTI on the PCB. The crystal oscillator is selected by shorting the pads on the OSC_CK side. The McASP clock by shorting the MCLK pads.

2. Oscillator Enable In case the master clock is supplied by the processor directly, it is possible to turn off the crystal oscillator. The configuration is marked as OSC_EN on the PCB. The crystal oscillator is turned off by shorting the pads marked gnd, and turned on by shorting the pads marked vcc.

3. Mic clock This option allows to give a clock 4x slower to the microphones. The configuration is marked as MIC_CK. This option is not used at the moment and the pads marked CKOUT should be shorted.

Dependencies

• A modifed linux kernel should be used. It can be found in another repo (branch epfl-3.14-sta321mp).
• A modified Device Tree Blob found in this repo (branch 3.14-ti-sta321mp).

Reuse

All the hardware is under CC-BY-SA 4.0 license. If you reuse some of this stuff in an academic context, please cite our demo proposal from ICASSP 2017.

E. Bezzam, R. Scheibler, J. Azcarreta, H. Pan, M. Simeoni, R. Beuchat, P. Hurley, B. Bruneau, C. Ferry, and S. Kashani, Hardware and software for reproducible research in audio array signal processing, Proc. IEEE ICASSP, New Orleans, LA, USA, 2017, pp. 6591--6592. DOI: 10.1109/ICASSP.2017.8005297