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1300 Henley Court Pullman, WA 99163 509.334.6306 www.digilentinc.com PmodMIC3 Reference Manual Revised April 12, 2016 This manual applies to the PmodMIC3 rev. A Overview The PmodMIC3 is a MEMS Microphone powered by the Knowles Acoustics SPA2410LR5H-B and the Texas Instruments ADCS7476. Users may adjust the incoming volume to the system board with the small potentiometer before they receive the 12 bits of data through SPI. Features include: MEMS Microphone module with digital interface Transform audio inputs with 12-bit A/D converter Adjust incoming volume with on-board potentiometer up to 1 MSPS of data Small PCB size for flexible designs 1.1 in 0.8 in (2.8 cm 2.0 cm) 6-pin Pmod port with SPI interface Follows Digilent Pmod Interface Specification Type 2 The PmodMIC3. 1 Functional Description The PmodMIC3 is designed to digitally report to the host board whenever it detects any external noise. By sending a 12-bit digital value representative of frequency and volume of the noise, this number can be processed by the system board and have the received sound accurately reproduced through a speaker. The on-board potentiometer can be used to modify the gain from the microphone into the ADC. Copyright Digilent, Inc. All rights reserved. DOC : 502-312 Page 1 of 3 Other product and company names mentioned may be trademarks of their respective owners. PmodMIC3 Reference Manual 2 Interfacing with the Pmod The PmodMIC3 communicates with the host board via the SPI protocol. The 12 bits of digital data are sent to the system board in 16 clock cycles with the most significant bit first. For the ADC7476, each bit is shifted out on each falling edge of the serial clock line after the chip select line is brought low with the first four bits as leading zeroes and the remaining 12 bits representing the 12 bits of data. The datasheet for the ADC7476 recommends that for faster microcontrollers or DSPs, the serial clock line is first brought to a high state before being brought low after the fall of the chip select line to ensure that the first bit is valid. More information about this can be found in the PmodMIC3 User Guide. Pin Signal Description 1 SS Chip select 2 NC Not connected 3 MISO Master-in slave-out 4 SCK Serial clock 5 GND Power supply ground 6 VCC Power supply (3.3V/5V) Table 1. Pinout table diagram. The PmodMIC3 is capable of converting up to 1 MSa per second of 12-bit data, making it an ideal Pmod to use in conjunction with the PmodI2S for an audio development application. Any external power applied to the PmodMIC3 must be within 3V and 5.5V to ensure that the on-board chips operate correctly however, it is recommended that Pmod is operated at 3.3V. A sample timing diagram taken from the ADCS7476 datasheet representing the data that will be received by the system board from the Pmod is shown in FIg. 1. Figure 1. Timing diagram. Copyright Digilent, Inc. All rights reserved. Page 2 of 3 Other product and company names mentioned may be trademarks of their respective owners.