USB audio on Teensy 4.0 (mostly kinda working now)

teensy4/usb.c

 	  case 0x0221:
 	  case 0x0321:
 	  case 0x0421:
-		endpoint0_receive(NULL, 0, 1); // handle these after ACK
-		return;
+		// TODO: remove this terrible kludge, but why oh why does servicing this
+		// request stop the isochronous endpoints?  Maybe a bug in endpoint0_receive?
+		if (usb_audio_transmit_setting || usb_audio_receive_setting) break; // kludge!!!
+
+		printf("set_feature, word1=%x, len=%d\n", setup.word1, setup.wLength);
+		if (setup.wLength <= sizeof(endpoint0_buffer)) {
+			endpoint0_setupdata.bothwords = setupdata;
+			endpoint0_receive(endpoint0_buffer, setup.wLength, 1);
+			return; // handle these after ACK
+		}
+		break;
 	  case 0x81A1: // GET FEATURE
 	  case 0x82A1:
 	  case 0x83A1:
 	  case 0x84A1:
 		if (setup.wLength <= sizeof(endpoint0_buffer)) {
-			/*if (usb_audio_get_feature(&setup, endpoint0_buffer, setup.wLength)) {
-				endpoint0_transmit(endpoint0_buffer, setup.wLength, 0);
+			uint32_t len;
+			static uint8_t buf[2];
+			if (usb_audio_get_feature(&setup, buf, &len)) {
+				printf("GET feature, len=%d\n", len);
+				endpoint0_transmit(buf, len, 0);
 				return;
-			}*/
+			}
 		}
 		break;
 	  case 0x81A2: // GET_CUR (wValue=0, wIndex=interface, wLength=len)
 	setup_t setup;
 
 	setup.bothwords = endpoint0_setupdata.bothwords;
-	//printf("complete %x %x %x\n", setup.word1, setup.word2, endpoint0_buffer[0]);
+	printf("complete %x %x %x\n", setup.word1, setup.word2, endpoint0_buffer[0]);
 #ifdef CDC_STATUS_INTERFACE
 	if (setup.wRequestAndType == 0x2021 /*CDC_SET_LINE_CODING*/) {
 		memcpy(usb_cdc_line_coding, endpoint0_buffer, 7);
 	}
 #endif
 #ifdef AUDIO_INTERFACE
-	// TODO: usb_audio_set_feature()
+	if (setup.word1 == 0x02010121 /* TODO: check setup.word2 */) {
+		usb_audio_set_feature(&endpoint0_setupdata, endpoint0_buffer);
+		// TODO: usb_audio_set_feature()
+	}
 #endif
 }
 

teensy4/usb_audio.cpp

 
 extern volatile uint8_t usb_high_speed;
 static void rx_event(transfer_t *t);
-static void rx_queue_transfer(void);
+static void tx_event(transfer_t *t);
 
 /*static*/ transfer_t rx_transfer __attribute__ ((used, aligned(32)));
 /*static*/ transfer_t sync_transfer __attribute__ ((used, aligned(32)));
+/*static*/ transfer_t tx_transfer __attribute__ ((used, aligned(32)));
 DMAMEM static uint8_t rx_buffer[AUDIO_RX_SIZE] __attribute__ ((aligned(32)));
-DMAMEM uint32_t usb_audio_sync_feedback;
+DMAMEM static uint8_t tx_buffer[AUDIO_RX_SIZE] __attribute__ ((aligned(32)));
+DMAMEM uint32_t usb_audio_sync_feedback __attribute__ ((aligned(32)));
 
 uint8_t usb_audio_receive_setting=0;
 uint8_t usb_audio_transmit_setting=0;
 {
 	if (t) {
 		int len = AUDIO_RX_SIZE - ((rx_transfer.status >> 16) & 0x7FFF);
-		//printf("rx %u\n", len);
+		printf("rx %u\n", len);
 		usb_audio_receive_callback(len);
 	}
 	usb_prepare_transfer(&rx_transfer, rx_buffer, AUDIO_RX_SIZE, 0);
 	//printf("sync %x\n", sync_transfer.status); // too slow, can't print this much
 	usb_audio_sync_feedback = feedback_accumulator >> usb_audio_sync_rshift;
 	usb_prepare_transfer(&sync_transfer, &usb_audio_sync_feedback, usb_audio_sync_nbytes, 0);
-	arm_dcache_delete(&usb_audio_sync_feedback, usb_audio_sync_nbytes);
+	arm_dcache_flush(&usb_audio_sync_feedback, usb_audio_sync_nbytes);
 	usb_transmit(AUDIO_SYNC_ENDPOINT, &sync_transfer);
 }
 
 	}
 	memset(&rx_transfer, 0, sizeof(rx_transfer));
 	usb_config_rx_iso(AUDIO_RX_ENDPOINT, AUDIO_RX_SIZE, 1, rx_event);
-	//rx_queue_transfer();
 	rx_event(NULL);
 	memset(&sync_transfer, 0, sizeof(sync_transfer));
 	usb_config_tx_iso(AUDIO_SYNC_ENDPOINT, usb_audio_sync_nbytes, 1, sync_event);
 	sync_event(NULL);
+	memset(&tx_transfer, 0, sizeof(tx_transfer));
+	usb_config_tx_iso(AUDIO_TX_ENDPOINT, AUDIO_TX_SIZE, 1, tx_event);
+	tx_event(NULL);
 }
 
 void AudioInputUSB::begin(void)
 	__enable_irq();
 	if (f) {
 		int diff = AUDIO_BLOCK_SAMPLES/2 - (int)c;
-		feedback_accumulator += diff * 2;
-
-		 //__disable_irq();
-		 //printf("fb:%x\n", feedback_accumulator);
-		 //__enable_irq();
+		feedback_accumulator += diff * 1;
 		//uint32_t feedback = (feedback_accumulator >> 8) + diff * 100;
 		//usb_audio_sync_feedback = feedback;
-		//if (diff > 0) {
-			//serial_print(".");
-		//} else if (diff < 0) {
-			//serial_print("^");
-		//}
+
+		//printf(diff >= 0 ? "." : "^");
 	}
 	//serial_phex(c);
 	//serial_print(".");
 	if (!left || !right) {
 		usb_audio_underrun_count++;
-		printf("#"); // buffer underrun - PC sending too slow
-		//if (f) feedback_accumulator += 10 << 8;
+		//printf("#"); // buffer underrun - PC sending too slow
+		if (f) feedback_accumulator += 3500;
 	}
 	if (left) {
 		transmit(left, 0);
 
 
 
-
-
-#if 0
+#if 1
 bool AudioOutputUSB::update_responsibility;
 audio_block_t * AudioOutputUSB::left_1st;
 audio_block_t * AudioOutputUSB::left_2nd;
 audio_block_t * AudioOutputUSB::right_2nd;
 uint16_t AudioOutputUSB::offset_1st;
 
+/*DMAMEM*/ uint16_t usb_audio_transmit_buffer[AUDIO_TX_SIZE/2] __attribute__ ((used, aligned(32)));
+
+
+static void tx_event(transfer_t *t)
+{
+	int len = usb_audio_transmit_callback();
+	usb_audio_sync_feedback = feedback_accumulator >> usb_audio_sync_rshift;
+	usb_prepare_transfer(&tx_transfer, usb_audio_transmit_buffer, len, 0);
+	arm_dcache_flush_delete(usb_audio_transmit_buffer, len);
+	usb_transmit(AUDIO_TX_ENDPOINT, &tx_transfer);
+}
 
-uint16_t usb_audio_transmit_buffer[AUDIO_TX_SIZE/2] DMABUFATTR;
 
 void AudioOutputUSB::begin(void)
 {
 	uint32_t avail, num, target, offset, len=0;
 	audio_block_t *left, *right;
 
-	if (++count < 9) {   // TODO: dynamic adjust to match USB rate
+	if (++count < 10) {   // TODO: dynamic adjust to match USB rate
 		target = 44;
 	} else {
 		count = 0;