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This code implements a USB speaker streaming audio to an I2S device, based on [Phil Schatzmann's port](https://www.pschatzmann.ch/home/2024/10/13/tinyusb-audio-on-an-rp2040-in-arduino/) of the TinyUSB Audio class for the rp2040.
This code uses the [Arduino pico](https://github.com/earlephilhower/arduino-pico) core, and two libraries:
- [Adafruit TinyUSB](https://github.com/pschatzmann/Adafruit_TinyUSB_Arduino/tree/Audio): this is the version modified by Phil Schatzmann to handle the Audio class on the rp2040.
- [I2S]: Arduino's standard I2S library.
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#include <Adafruit_TinyUSB.h>
#include <I2S.h>
#define I2S_CLK 1
#define I2S_FRAME (I2S_CLK+1)
#define I2S_DATA 4
#define SAMPLE_RATE 44100
#define SAMPLE_BITS 16
Adafruit_USBD_Audio usb;
I2S i2s(OUTPUT);
size_t writeCB(const uint8_t* data, size_t len, Adafruit_USBD_Audio& ref) {
int16_t* data16 = (int16_t*)data;
size_t n_written = i2s.write(data, len);
// returns the amount written (and convert to bytes)
return n_written * 2 * sizeof(int16_t);
}
void setup() {
// init USB
if (!TinyUSBDevice.isInitialized()) {
TinyUSBDevice.begin(0);
}
Serial.begin(115200);
// reconfigure USB
usb.setWriteCallback(writeCB);
usb.begin(SAMPLE_RATE, 2, SAMPLE_BITS);
if (TinyUSBDevice.mounted()) {
TinyUSBDevice.detach();
delay(10);
TinyUSBDevice.attach();
}
// start I2S
i2s.setBCLK(I2S_CLK);
i2s.setDATA(I2S_DATA);
i2s.setBitsPerSample(SAMPLE_BITS);
i2s.begin(SAMPLE_RATE);
}
void loop() {
#ifdef TINYUSB_NEED_POLLING_TASK
TinyUSBDevice.task();
#endif
}