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I will generate an output clock signal to the microphone on one pin and use another pin to receive data from the microphone.
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While the RP2040 does not have built-in support for both of these interface types, the super flexible Programmable I/O (PIO) feature can be used to create our own PDM or I2S peripheral interface in software. There are two common interfaces for digital microphones: The RP2040 MCU has a built-in 4 channel Analog-to-digital converter (ADC) feature with 12-bit precision, this could be used to collect audio from an external analog microphone, however we found the audio quality from the analog microphone to contain a lot of noise, so will be using a digital microphone instead. We can use it's built in USB Audio Class support to transform our Pico into a USB microphone device. and has support for both device and host mode. The Tiny USB library is "An open source cross-platform USB stack for embedded system" that supports several types of MCU's including the Raspberry Pi RP2040. The Raspberry Pi Pico SDK uses the TinyUSB library as its USB software stack.
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The Raspberry Pi Pico board's RP2040 MCU has a "USB 1.1 Host/Device" feature, which allows you to either connect to an existing USB peripheral device (host mode) or create your own USB peripheral (device mode). USB is an extremely popular standard, released in 1996, for wired computer peripherals, such as keyboards, mice, printers, scanners, and microphones. This project will leverage the Programming I/O (PIO), Direct Memory Access (DMA), and Universal Serial Bus (USB) capabilities of the boards RP2040 microcontroller (MCU). This guide will walk through how to create your own USB microphone device using a Raspberry Pi Pico board and an external digital microphone. This guide was created on behalf of the Arm Software Developers team, follow us on Twitter: and YouTube: Arm Software Developers for more resources!
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