diff --git a/src/stm32/cdcacm.c b/src/stm32/cdcacm.c
index 0ecb5532..962bd06f 100644
--- a/src/stm32/cdcacm.c
+++ b/src/stm32/cdcacm.c
@@ -28,6 +28,7 @@
 
 #include <libopencm3/stm32/f1/rcc.h>
 #include <libopencm3/stm32/nvic.h>
+#include <libopencm3/stm32/exti.h>
 #include <libopencm3/stm32/f1/gpio.h>
 #include <libopencm3/usb/usbd.h>
 #include <libopencm3/usb/cdc.h>
@@ -436,8 +437,6 @@ static int cdcacm_control_request(struct usb_setup_data *req, uint8_t **buf,
 #endif
 	case DFU_GETSTATUS: 
 		if(req->wIndex == DFU_IF_NO) {
-			u32 bwPollTimeout = 0; /* 24-bit integer in DFU class spec */
-
 			(*buf)[0] = DFU_STATUS_OK;
 			(*buf)[1] = 0;
 			(*buf)[2] = 0;
@@ -526,6 +525,8 @@ uint8_t usbd_control_buffer[256];
 
 void cdcacm_init(void)
 {
+	void exti15_10_isr(void);
+
 	get_dev_unique_id(serial_no);
 
 	usbd_init(&stm32f103_usb_driver, &dev, &config, usb_strings);
@@ -533,10 +534,20 @@ void cdcacm_init(void)
 	usbd_register_set_config_callback(cdcacm_set_config);
 
 	nvic_enable_irq(NVIC_USB_LP_CAN_RX0_IRQ);
+	nvic_enable_irq(USB_VBUS_IRQ);
 
+	gpio_set(USB_VBUS_PORT, USB_VBUS_PIN);
 	gpio_set(USB_PU_PORT, USB_PU_PIN);
-	gpio_set_mode(USB_PU_PORT, GPIO_MODE_OUTPUT_10_MHZ, 
-			GPIO_CNF_OUTPUT_PUSHPULL, USB_PU_PIN);
+
+	gpio_set_mode(USB_VBUS_PORT, GPIO_MODE_INPUT, 
+			GPIO_CNF_INPUT_PULL_UPDOWN, USB_VBUS_PIN);
+
+	/* Configure EXTI for USB VBUS monitor */
+	exti_select_source(USB_VBUS_PIN, USB_VBUS_PORT);
+	exti_set_trigger(USB_VBUS_PIN, EXTI_TRIGGER_BOTH);
+	exti_enable_request(USB_VBUS_PIN);
+
+	exti15_10_isr();
 }
 
 void usb_lp_can_rx0_isr(void)
@@ -544,6 +555,21 @@ void usb_lp_can_rx0_isr(void)
 	usbd_poll();
 }
 
+void exti15_10_isr(void)
+{
+	if (gpio_get(USB_VBUS_PORT, USB_VBUS_PIN)) {
+		/* Drive pull-up high if VBUS connected */
+		gpio_set_mode(USB_PU_PORT, GPIO_MODE_OUTPUT_10_MHZ, 
+				GPIO_CNF_OUTPUT_PUSHPULL, USB_PU_PIN);
+	} else {
+		/* Allow pull-up to float if VBUS disconnected */
+		gpio_set_mode(USB_PU_PORT, GPIO_MODE_INPUT, 
+				GPIO_CNF_INPUT_FLOAT, USB_PU_PIN);
+	}
+
+	exti_reset_request(USB_VBUS_PIN);
+}
+
 static char *get_dev_unique_id(char *s) 
 {
         volatile uint32_t *unique_id_p = (volatile uint32_t *)0x1FFFF7E8;
diff --git a/src/stm32/platform.h b/src/stm32/platform.h
index 85ade4f0..075717c5 100644
--- a/src/stm32/platform.h
+++ b/src/stm32/platform.h
@@ -41,7 +41,7 @@
  * LED1 = 	PB10	(Yellow LED : Idle)
  * LED2 = 	PB11	(Red LED    : Error)
  *
- * TPWR = 	RB0 (input)
+ * TPWR = 	RB0 (input) -- analogue on mini design ADC1, ch8
  * nTRST = 	PB1
  * SRST_OUT = 	PA2
  * TDI = 	PA3
@@ -50,7 +50,9 @@
  * TDO = 	PA6 (input)
  * nSRST = 	PA7 (input)
  *
- * USB cable pull-up: PA8	// was PA10 on prototype
+ * USB cable pull-up: PA8
+ * USB VBUS detect:  PB13 -- New on mini design.  
+ *                           Enable pull up for compatibility.
  * Force DFU mode button: PB12
  */
 
@@ -68,6 +70,10 @@
 #define USB_PU_PORT	GPIOA
 #define USB_PU_PIN	GPIO8
 
+#define USB_VBUS_PORT	GPIOB
+#define USB_VBUS_PIN	GPIO13
+#define USB_VBUS_IRQ	NVIC_EXTI15_10_IRQ
+
 #define LED_PORT	GPIOB
 #define LED_RUN	GPIO2
 #define LED_IDLE	GPIO10