diff --git a/atusb/fw/board.h b/atusb/fw/board.h
index 9f16e5a..09ec915 100644
--- a/atusb/fw/board.h
+++ b/atusb/fw/board.h
@@ -73,6 +73,7 @@
 #define	HAS_BOARD_SERNUM
 
 extern uint8_t board_sernum[42];
+extern uint8_t irq_serial;
 
 
 void reset_rf(void);
diff --git a/atusb/fw/board_app.c b/atusb/fw/board_app.c
index 80eed69..22b93c3 100644
--- a/atusb/fw/board_app.c
+++ b/atusb/fw/board_app.c
@@ -150,13 +150,15 @@ static void done(void *user)
 }
 
 
+uint8_t irq_serial;
+
+
 ISR(INT0_vect)
 {
-	static uint8_t buf;
-
 	if (eps[1].state == EP_IDLE) {
 		led(1);
-		usb_send(&eps[1], &buf, 1, done, NULL);
+		irq_serial++;
+		usb_send(&eps[1], &irq_serial, 1, done, NULL);
 	}
 }
 
diff --git a/atusb/fw/ep0.c b/atusb/fw/ep0.c
index 83ab075..c1be341 100644
--- a/atusb/fw/ep0.c
+++ b/atusb/fw/ep0.c
@@ -217,6 +217,16 @@ static int my_setup(const struct setup_request *setup)
 		else
 			do_buf_write(NULL);
 		return 1;
+	case ATUSB_FROM_DEV(ATUSB_SPI_WRITE2_SYNC):
+		spi_begin();
+		spi_send(setup->wValue);
+		spi_send(setup->wIndex);
+		spi_end();
+		buf[0] = irq_serial;
+		if (setup->wLength)
+			usb_send(&eps[0], buf, 1, NULL, NULL);
+		return 1;
+
 	case ATUSB_FROM_DEV(ATUSB_SPI_READ1):
 	case ATUSB_FROM_DEV(ATUSB_SPI_READ2):
 		spi_begin();
diff --git a/atusb/fw/include/atusb/ep0.h b/atusb/fw/include/atusb/ep0.h
index 391b114..55bc222 100644
--- a/atusb/fw/include/atusb/ep0.h
+++ b/atusb/fw/include/atusb/ep0.h
@@ -39,6 +39,7 @@
  * host->	ATUSB_SPI_WRITE		byte0		byte1	#bytes
  * ->host	ATUSB_SPI_READ1		byte0		-	#bytes
  * ->host	ATUSB_SPI_READ2		byte0		byte1	#bytes
+ * ->host	ATUSB_SPI_WRITE2_SYNC	byte0		bute1	0/1
  */
 
 /*
@@ -91,6 +92,7 @@ enum atspi_requests {
 	ATUSB_SPI_WRITE			= 0x30,	/* SPI group */
 	ATUSB_SPI_READ1,
 	ATUSB_SPI_READ2,
+	ATUSB_SPI_WRITE2_SYNC,
 };