Function initialiseI2S

samples/Basic_Audio/app/application.cpp:167–242

}

void initialiseI2S()
{
	i2s_config_t config;
	memset(&config, 0, sizeof(config));
	const i2s_module_config_t modcfg = {
		.mode = I2S_MODE_MASTER,
		.bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
		.channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
		.communication_format = I2S_COMM_FORMAT_I2S_MSB,
		.dma_buf_len = 128,
		.dma_buf_count = 4,
		.callback_threshold = 1,
	};

	/*
	 * Not clear exactly what this setting does.
	 * I think, additional bits written out.
	 *
	 * For example, 16-bit channel data + bits_mod=8 produces 24-bits per channel.
	 * Where do additional 8 bits come from? Scope says 0.
	 */
	config.bits_mod = 16;

	config.tx = modcfg;
	config.sample_rate = targetSampleRate;
	//	config.rx = modcfg;
	//	config.rx.mode = I2S_MODE_SLAVE;
	//	config.tx_desc_auto_clear = true;
	//	config.auto_start = true;
	config.callback = i2sCallback;
	config.param = nullptr; // If you want to pass a parameter to the callback routine
	if(!i2s_driver_install(&config)) {
		debug_e("i2s_driver_install failed");
		return;
	}

#ifdef ENABLE_DELTA_SIGMA
	// We're doing delta mod so only need one pin
	i2s_set_pins(I2S_PIN_DATA_OUT, true);
#else
	// Real I2S DACs require channel select (assuming its stereo) and clock lines
	i2s_set_pins(I2S_PIN_DATA_OUT | I2S_PIN_WS_OUT | I2S_PIN_BCK_OUT, true);
#endif

	auto realSampleRate = i2s_get_real_rate();
	Serial << _F("I2S initialised, rate = ") << realSampleRate << endl;

#ifndef GENERATE_FIXED_VALUES
	/*
	 * Generate sine wave data using the actual sample rate, which may be
	 * different to that requested.
	 */
	if(!sineWaveTable.generate(realSampleRate, sineWaveFrequency)) {
		return;
	}
#endif

	// Pre-fill the buffers