I2S mic to USB audio (nRF5 SDK v17.0.2)

Question

Hello, 
 nRF5 SDK v17.0.2, Keil5 
 USB audio demo and I2S demo, 
 i2s cannect two mic(L and R), 16bit 48K STEREO, 
 how to put i2s data to usb audio? 
 i add function to USB audio demo as follow: 
 uint16_t usb_put_data(const uint16_t* p_buff, uint16_t size)
{
 ret_code_t ret = app_usbd_audio_class_tx_start(&m_app_audio_microphone.base, p_buff, size*2);
 if (NRF_SUCCESS == ret)
	{
 //bsp_board_led_invert(LED_AUDIO_RX);
	}
	return size;
} 
 don't know if it sucess, so some audio data lost. 
 it note This function should be called in reaction to a SOF event. 
 where the SOF? 
 int hp_sof_ev_handler(uint16_t framecnt) 
 or 
 usbd_user_ev_handler(app_usbd_event_type_t event) ---> case APP_USBD_EVT_DRV_SOF:

How to do it specifically? 
 
 Best regards

yoyou · Accepted Answer

Hi 
 app_usbd_audio_class_tx_start() return code same time 17 or 8. 
 now i2s put audio to usb audio already worked, 
 My solution is: 
 1.usb audio one frame 192 Byte, i2s the same 192 Byte, (the same frame length). 
 2.call app_usbd_audio_class_tx_start() in _sof_ev_handler(uint16_t framecnt) ,and retain data until successfully sent that (NRF_SUCCESS == ret). 
 
 last question: is i2s not support 24bit 48Khz? 
 config.format = NRF_I2S_FORMAT_I2S;
 config.alignment = NRF_I2S_ALIGN_LEFT;
 config.mode = NRF_I2S_MODE_MASTER;
 config.ratio = NRF_I2S_RATIO_32X;
	config.mck_setup = NRF_I2S_MCK_32MDIV21;
	config.channels = NRF_I2S_CHANNELS_STEREO;
	config.sample_width = NRF_I2S_SWIDTH_24BIT;

thanks 
 Best regards

I2S mic to USB audio (nRF5 SDK v17.0.2)

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