Add usb audio asychronous feedback endpoint (fixed data for now)

teensy3/usb_audio.cpp

 #define DMABUFATTR __attribute__ ((section(".dmabuffers"), aligned (4)))
 uint16_t usb_audio_receive_buffer[AUDIO_RX_SIZE/2] DMABUFATTR;
 uint16_t usb_audio_transmit_buffer[AUDIO_TX_SIZE/2] DMABUFATTR;
+uint32_t usb_audio_sync_feedback DMABUFATTR;
 
 void AudioInputUSB::begin(void)
 {
 	// but also because the PC may stop transmitting data, which
 	// means we no longer get receive callbacks from usb_dev.
 	update_responsibility = false;
+	usb_audio_sync_feedback = 722824;
 }
 
 static void copy_to_buffers(const uint32_t *src, int16_t *left, int16_t *right, unsigned int len)
 	audio_block_t *left, *right;
 	const uint32_t *data;
 
-	//return;
-
 	len >>= 2; // 1 sample = 4 bytes: 2 left, 2 right
 	data = (const uint32_t *)usb_audio_receive_buffer;
 
 			copy_to_buffers(data, left->data + count, right->data + count, avail);
 			data += avail;
 			len -= avail;
-			if (AudioInputUSB::ready_left)
+			if (AudioInputUSB::ready_left) // buffer overrun, PC sending too fast
 				AudioStream::release(AudioInputUSB::ready_left);
 			AudioInputUSB::ready_left = left;
 			if (AudioInputUSB::ready_right)
 	right = ready_right;
 	ready_right = NULL;
 	// TODO: use incoming_count for USB isochronous feedback
+	uint16_t c = incoming_count;
 	__enable_irq();
-	//if (left && right) {
-		//serial_print("$");
-	//} else {
-		//serial_print("#");
-	//}
+	//serial_phex(c);
+	//serial_print(".");
+	if (!left || !right) {
+		//serial_print("#"); // buffer underrun - PC sending too slow
+	}
 	if (left) {
 		transmit(left, 0);
 		release(left);

teensy3/usb_audio.h

 extern uint16_t usb_audio_transmit_buffer[];
 extern void usb_audio_receive_callback(unsigned int len);
 extern unsigned int usb_audio_transmit_callback(void);
+extern uint32_t usb_audio_sync_feedback;
 #ifdef __cplusplus
 }
 

teensy3/usb_desc.c

 
 #define AUDIO_INTERFACE_DESC_POS	KEYMEDIA_INTERFACE_DESC_POS+KEYMEDIA_INTERFACE_DESC_SIZE
 #ifdef  AUDIO_INTERFACE
-#define AUDIO_INTERFACE_DESC_SIZE	9+10+12+9+12+9 + 9+9+7+11+9+7 + 9+9+7+11+9+7
+#define AUDIO_INTERFACE_DESC_SIZE	9+10+12+9+12+9 + 9+9+7+11+9+7 + 9+9+7+11+9+7+9
 #else
 #define AUDIO_INTERFACE_DESC_SIZE	0
 #endif
 	1,					// bSamFreqType = 1 frequency
 	LSB(44100), MSB(44100), 0,		// tSamFreq
 	// Standard AS Isochronous Audio Data Endpoint Descriptor
-	// SB DCD for Audio Devices 1.0, Section 4.6.1.1, Table 4-20, page 61-62
+	// USB DCD for Audio Devices 1.0, Section 4.6.1.1, Table 4-20, page 61-62
 	9, 					// bLength
 	5, 					// bDescriptorType, 5 = ENDPOINT_DESCRIPTOR
 	AUDIO_TX_ENDPOINT | 0x80,		// bEndpointAddress
 	4,					// bDescriptorType = INTERFACE
 	AUDIO_INTERFACE+2,			// bInterfaceNumber
 	1,					// bAlternateSetting
-	1,					// bNumEndpoints
+	2,					// bNumEndpoints
 	1,					// bInterfaceClass, 1 = AUDIO
 	2,					// bInterfaceSubclass, 2 = AUDIO_STREAMING
 	0,					// bInterfaceProtocol
 	1,					// bSamFreqType = 1 frequency
 	LSB(44100), MSB(44100), 0,		// tSamFreq
 	// Standard AS Isochronous Audio Data Endpoint Descriptor
-	// SB DCD for Audio Devices 1.0, Section 4.6.1.1, Table 4-20, page 61-62
+	// USB DCD for Audio Devices 1.0, Section 4.6.1.1, Table 4-20, page 61-62
 	9, 					// bLength
 	5, 					// bDescriptorType, 5 = ENDPOINT_DESCRIPTOR
 	AUDIO_RX_ENDPOINT,			// bEndpointAddress
 	LSB(AUDIO_RX_SIZE), MSB(AUDIO_RX_SIZE),	// wMaxPacketSize
 	1,			 		// bInterval, 1 = every frame
 	0,					// bRefresh
-	0,					// bSynchAddress
+	AUDIO_SYNC_ENDPOINT | 0x80,		// bSynchAddress
 	// Class-Specific AS Isochronous Audio Data Endpoint Descriptor
 	// USB DCD for Audio Devices 1.0, Section 4.6.1.2, Table 4-21, page 62-63
 	7,  					// bLength
 	0x01,  					// bmAttributes = Sampling Frequency
 	1,  					// bLockDelayUnits, 1 = ms
 	0x30, 0x00,  				// wLockDelay
+	// Standard AS Isochronous Audio Synch Endpoint Descriptor
+	// USB DCD for Audio Devices 1.0, Section 4.6.2.1, Table 4-22, page 63-64
+	9, 					// bLength
+	5, 					// bDescriptorType, 5 = ENDPOINT_DESCRIPTOR
+	AUDIO_SYNC_ENDPOINT | 0x80,		// bEndpointAddress
+	0x01, 					// bmAttributes = isochronous
+	3, 0,					// wMaxPacketSize, 3 bytes
+	1,			 		// bInterval, 1 = every frame
+	1,					// bRefresh, 1=2ms, 2=8ms
+	0,					// bSynchAddress
 #endif
 };
 

teensy3/usb_desc.h

   #define PRODUCT_NAME		{'T','e','e','n','s','y',' ','A','u','d','i','o'}
   #define PRODUCT_NAME_LEN	12
   #define EP0_SIZE		64
-  #define NUM_ENDPOINTS         4
+  #define NUM_ENDPOINTS         5
   #define NUM_USB_BUFFERS	16
   #define NUM_INTERFACE		4
   #define SEREMU_INTERFACE      3	// Serial emulation
   #define AUDIO_TX_SIZE         180
   #define AUDIO_RX_ENDPOINT     4
   #define AUDIO_RX_SIZE         180
+  #define AUDIO_SYNC_ENDPOINT	5
   #define ENDPOINT1_CONFIG	ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT2_CONFIG	ENDPOINT_RECEIVE_ONLY
   #define ENDPOINT3_CONFIG	ENDPOINT_TRANSMIT_ISOCHRONOUS
   #define ENDPOINT4_CONFIG	ENDPOINT_RECEIVE_ISOCHRONOUS
+  #define ENDPOINT5_CONFIG	ENDPOINT_TRANSMIT_ISOCHRONOUS
 
 #endif
 

teensy3/usb_dev.c

 			}
 			table[index(i, TX, EVEN)].desc = 0;
 			table[index(i, TX, ODD)].desc = 0;
+#ifdef AUDIO_INTERFACE
+			if (i == AUDIO_SYNC_ENDPOINT) {
+				table[index(i, TX, EVEN)].addr = &usb_audio_sync_feedback;
+				table[index(i, TX, EVEN)].desc = (3<<16) | BDT_OWN;
+			}
+#endif
 		}
 		break;
 	  case 0x0880: // GET_CONFIGURATION
 				usb_audio_receive_callback(b->desc >> 16);
 				b->addr = usb_audio_receive_buffer;
 				b->desc = (AUDIO_RX_SIZE << 16) | BDT_OWN;
+			} else if ((endpoint == AUDIO_SYNC_ENDPOINT-1) && (stat & 0x08)) {
+				b = (bdt_t *)((uint32_t)b ^ 8);
+				b->addr = &usb_audio_sync_feedback;
+				b->desc = (3 << 16) | BDT_OWN;
+				tx_state[endpoint] ^= 1;
 			} else
 #endif
 			if (stat & 0x08) { // transmit

teensy3/usb_dev.h

 #ifdef AUDIO_INTERFACE
 extern uint16_t usb_audio_receive_buffer[];
 extern uint16_t usb_audio_transmit_buffer[];
+extern uint32_t usb_audio_sync_feedback;
 extern void usb_audio_receive_callback(unsigned int len);
 extern unsigned int usb_audio_transmit_callback(void);
 #endif