Improve MIDI transmit speed

USBHost_t36.h

 	uint32_t started_micros; // testing only
 private:
 	USBDriver      *driver;
-	USBHIDInput	   *hidinput;
+	USBHIDInput    *hidinput;
 	uint32_t       usec;
 	USBDriverTimer *next;
 	USBDriverTimer *prev;
 	};
 	MIDIDeviceBase(USBHost &host, uint32_t *rx, uint32_t *tx1, uint32_t *tx2,
 		uint16_t bufsize, uint32_t *rqueue, uint16_t qsize) :
-			rx_buffer(rx), tx_buffer1(tx1), tx_buffer2(tx2),
+			txtimer(this), rx_buffer(rx), tx_buffer1(tx1), tx_buffer2(tx2),
 			rx_queue(rqueue), max_packet_size(bufsize), rx_queue_size(qsize) {
 				init();
 		}
 protected:
 	virtual bool claim(Device_t *device, int type, const uint8_t *descriptors, uint32_t len);
 	virtual void disconnect();
+	virtual void timer_event(USBDriverTimer *timer);
 	static void rx_callback(const Transfer_t *transfer);
 	static void tx_callback(const Transfer_t *transfer);
 	void rx_data(const Transfer_t *transfer);
 private:
 	Pipe_t *rxpipe;
 	Pipe_t *txpipe;
+	USBDriverTimer txtimer;
 	//enum { MAX_PACKET_SIZE = 64 };
 	//enum { RX_QUEUE_SIZE = 80 }; // must be more than MAX_PACKET_SIZE/4
 	//uint32_t rx_buffer[MAX_PACKET_SIZE/4];

ehci.cpp

 	USBHS_PERIODICLISTBASE = (uint32_t)periodictable;
 	USBHS_FRINDEX = 0;
 	USBHS_ASYNCLISTADDR = 0;
-	USBHS_USBCMD = USBHS_USBCMD_ITC(8) | USBHS_USBCMD_RS |
+	USBHS_USBCMD = USBHS_USBCMD_ITC(0) | USBHS_USBCMD_RS |
 		USBHS_USBCMD_ASP(3) | USBHS_USBCMD_ASPE | USBHS_USBCMD_PSE |
 		#if PERIODIC_LIST_SIZE == 8
 		USBHS_USBCMD_FS2 | USBHS_USBCMD_FS(3);

midi.cpp

 	if (!txpipe) return;
 	uint32_t tx_max = tx_size / 4;
 	while (1) {
+		__disable_irq();
 		uint32_t tx1 = tx1_count;
 		uint32_t tx2 = tx2_count;
 		if (tx1 < tx_max && (tx2 == 0 || tx2 >= tx_max)) {
 			// use tx_buffer1
 			tx_buffer1[tx1++] = data;
 			tx1_count = tx1;
-                        __disable_irq();
+			txtimer.stop();
 			if (tx1 >= tx_max) {
 				queue_Data_Transfer(txpipe, tx_buffer1, tx_max*4, this);
 			} else {
-				// TODO: start a timer, rather than sending the buffer
-				// before it's full, to make best use of bandwidth
-				tx1_count = tx_max;
-				queue_Data_Transfer(txpipe, tx_buffer1, tx_max*4, this);
+				txtimer.start(tx_max >= 128 ? 200 : 1500);
 			}
-                        __enable_irq();
+			__enable_irq();
 			return;
 		}
 		if (tx2 < tx_max) {
 			// use tx_buffer2
 			tx_buffer2[tx2++] = data;
 			tx2_count = tx2;
-                        __disable_irq();
+			txtimer.stop();
 			if (tx2 >= tx_max) {
 				queue_Data_Transfer(txpipe, tx_buffer2, tx_max*4, this);
 			} else {
-				// TODO: start a timer, rather than sending the buffer
-				// before it's full, to make best use of bandwidth
-				tx2_count = tx_max;
-				queue_Data_Transfer(txpipe, tx_buffer2, tx_max*4, this);
+				txtimer.start(tx_max >= 128 ? 200 : 1500);
 			}
-                        __enable_irq();
+			__enable_irq();
 			return;
 		}
+		__enable_irq();
+		// TODO: call yield() ??
+	}
+}
+
+void MIDIDeviceBase::timer_event(USBDriverTimer *timer)
+{
+	const uint32_t tx_max = tx_size / 4;
+	uint32_t tx1 = tx1_count;
+	if (tx1 > 0) {
+		tx1_count = tx_max;
+		queue_Data_Transfer(txpipe, tx_buffer1, tx1*4, this);
+	}
+	uint32_t tx2 = tx2_count;
+	if (tx2 > 0) {
+		tx2_count = tx_max;
+		queue_Data_Transfer(txpipe, tx_buffer2, tx2*4, this);
 	}
 }