T4 USB MIDI auto flush output at start of microframe

teensy4/usb.c

 volatile uint8_t usb_configuration = 0; // non-zero when USB host as configured device
 volatile uint8_t usb_high_speed = 0;    // non-zero if running at 480 Mbit/sec speed
 static uint8_t endpoint0_buffer[8];
+static uint8_t sof_usage = 0;
 static uint8_t usb_reboot_timer = 0;
 
 extern uint8_t usb_descriptor_buffer[]; // defined in usb_desc.c
 		printf("sof %d\n", usb_reboot_timer);
 		if (usb_reboot_timer) {
 			if (--usb_reboot_timer == 0) {
+				usb_stop_sof_interrupts(NUM_INTERFACE);
 				asm("bkpt #251"); // run bootloader
 			}
-		} else {
-			// turn off the SOF interrupt if nothing using it
-			USB1_USBINTR &= ~USB_USBINTR_SRE;
 		}
+		#ifdef MIDI_INTERFACE
+		usb_midi_flush_output();
+		#endif
 	}
 }
 
 
+void usb_start_sof_interrupts(int interface)
+{
+	__disable_irq();
+	sof_usage |= (1 << interface);
+	uint32_t intr = USB1_USBINTR;
+	if (!(intr & USB_USBINTR_SRE)) {
+		USB1_USBSTS = USB_USBSTS_SRI; // clear prior SOF before SOF IRQ enable
+		USB1_USBINTR = intr | USB_USBINTR_SRE;
+	}
+	__enable_irq();
+}
+
+void usb_stop_sof_interrupts(int interface)
+{
+	sof_usage &= ~(1 << interface);
+	if (sof_usage == 0) {
+		USB1_USBINTR &= ~USB_USBINTR_SRE;
+	}
+}
+
+
+
+
 /*
 struct transfer_struct { // table 55-60, pg 3159
 	uint32_t next;
 		memcpy(usb_cdc_line_coding, endpoint0_buffer, 7);
 		printf("usb_cdc_line_coding, baud=%u\n", usb_cdc_line_coding[0]);
 		if (usb_cdc_line_coding[0] == 134) {
-			USB1_USBINTR |= USB_USBINTR_SRE;
+			usb_start_sof_interrupts(NUM_INTERFACE);
 			usb_reboot_timer = 80; // TODO: 10 if only 12 Mbit/sec
 		}
 	}
 	  && endpoint0_buffer[0] == 0xA9 && endpoint0_buffer[1] == 0x45
 	  && endpoint0_buffer[2] == 0xC2 && endpoint0_buffer[3] == 0x6B) {
 		printf("seremu reboot request\n");
-		USB1_USBINTR |= USB_USBINTR_SRE;
+		usb_start_sof_interrupts(NUM_INTERFACE);
 		usb_reboot_timer = 80; // TODO: 10 if only 12 Mbit/sec
 	}
 #endif

teensy4/usb_desc.c

 
 
 __attribute__ ((section(".dmabuffers"), aligned(32)))
-uint8_t usb_descriptor_buffer[CONFIG_DESC_SIZE + 4096];
+uint8_t usb_descriptor_buffer[CONFIG_DESC_SIZE];
 
 
 

teensy4/usb_dev.h

 void usb_receive(int endpoint_number, transfer_t *transfer);
 uint32_t usb_transfer_status(const transfer_t *transfer);
 
+void usb_start_sof_interrupts(int interface);
+void usb_stop_sof_interrupts(int interface);
+
 extern void (*usb_timer0_callback)(void);
 extern void (*usb_timer1_callback)(void);
 

teensy4/usb_midi.c

 	rx_tail = 0;
 	rx_available = 0;
 	usb_config_rx(MIDI_RX_ENDPOINT, rx_packet_size, 0, rx_event);
-	usb_config_tx(MIDI_TX_ENDPOINT, tx_packet_size, 1, NULL);
-	int i;
+	usb_config_tx(MIDI_TX_ENDPOINT, tx_packet_size, 0, NULL); // TODO: is ZLP needed?
+	//int i;
 	//for (i=0; i < RX_NUM; i++) rx_queue_transfer(i);
 	// TODO: set up SOF interrupt....
 	transmit_previous_timeout = 0;
 		usb_transmit(MIDI_TX_ENDPOINT, xfer);
 		if (++head >= TX_NUM) head = 0;
 		tx_head = head;
+		usb_stop_sof_interrupts(MIDI_INTERFACE);
+	} else {
+		usb_start_sof_interrupts(MIDI_INTERFACE);
 	}
 	tx_noautoflush = 0;
 }
 
 void usb_midi_flush_output(void)
 {
-	printf("usb_midi_flush_output\n");
+	//printf("usb_midi_flush_output\n");
 	if (tx_noautoflush == 0 && tx_available > 0) {
 		printf(" tx, %d %d\n", tx_packet_size, tx_available);
 		uint32_t head = tx_head;
 		if (++head >= TX_NUM) head = 0;
 		tx_head = head;
 		tx_available = 0;
+		usb_stop_sof_interrupts(MIDI_INTERFACE);
 	}
 }
 
 
 int usb_midi_read(uint32_t channel)
 {
-	uint32_t n, index, ch, type1, type2, b1;
+	//uint32_t n, index, ch, type1, type2, b1;
+	uint32_t n, ch, type1, type2, b1;
 	
 	return 0;
 #if 0