diff --git a/scripts/flash_usb.py b/scripts/flash_usb.py
index 9f1a7ea6..4fc72716 100755
--- a/scripts/flash_usb.py
+++ b/scripts/flash_usb.py
@@ -188,9 +188,21 @@ def flash_stm32f1(options, binfile):
             options.device, str(e), options.device))
         sys.exit(-1)
 
+STM32F4_HELP = """
+USB flash is not supported on the STM32F4!
+
+If attempting to flash via 3.3V serial, then use:
+  make serialflash FLASH_DEVICE=%s
+
+"""
+
+def flash_stm32f4(options, binfile):
+    sys.stderr.write(STM32F4_HELP % (options.device,))
+    sys.exit(-1)
+
 MCUTYPES = {
     'atsam3': flash_atsam3, 'atsam4': flash_atsam4, 'atsamd': flash_atsamd,
-    'lpc176x': flash_lpc176x, 'stm32f1': flash_stm32f1
+    'lpc176x': flash_lpc176x, 'stm32f1': flash_stm32f1, 'stm32f4': flash_stm32f4
 }
 
 
diff --git a/src/stm32f4/Kconfig b/src/stm32f4/Kconfig
index 53b7967c..de60e4fa 100644
--- a/src/stm32f4/Kconfig
+++ b/src/stm32f4/Kconfig
@@ -19,6 +19,7 @@ choice
     config MACH_STM32F103
         bool "STM32F103"
         select MACH_STM32F1xx
+        select HAVE_STM32_USBFS
     config MACH_STM32F405
         bool "STM32F405"
         select MACH_STM32F4xx
@@ -34,6 +35,8 @@ config MACH_STM32F1xx
     bool
 config MACH_STM32F4xx
     bool
+config HAVE_STM32_USBFS
+    bool
 
 config MCU
     string
@@ -64,6 +67,21 @@ config STACK_SIZE
     int
     default 512
 
+choice
+    prompt "Bootloader offset" if MACH_STM32F103
+    config STM32_FLASH_START_2000
+        bool "8KiB bootloader (stm32duino)"
+    config STM32_FLASH_START_7000
+        bool "28KiB bootloader"
+    config STM32_FLASH_START_0000
+        bool "No bootloader"
+endchoice
+config FLASH_START
+    hex
+    default 0x2000 if STM32_FLASH_START_2000
+    default 0x7000 if STM32_FLASH_START_7000
+    default 0x0000
+
 choice
     prompt "Clock Reference" if LOW_LEVEL_OPTIONS
     config STM32_CLOCK_REF_8M
@@ -76,7 +94,12 @@ config CLOCK_REF_8M
     default n if STM32_CLOCK_REF_INTERNAL
     default y
 
+config USBSERIAL
+    bool "Use USB for communication (instead of serial)"
+    depends on HAVE_STM32_USBFS
+    default y
 config SERIAL
+    depends on !USBSERIAL
     bool
     default y
 choice
diff --git a/src/stm32f4/Makefile b/src/stm32f4/Makefile
index d91a0f43..e39574b2 100644
--- a/src/stm32f4/Makefile
+++ b/src/stm32f4/Makefile
@@ -26,6 +26,7 @@ src-$(CONFIG_MACH_STM32F4xx) += ../lib/stm32f4/system_stm32f4xx.c
 src-$(CONFIG_MACH_STM32F4xx) += stm32f4/clock.c
 src-$(CONFIG_HAVE_GPIO_ADC) += stm32f4/adc.c
 src-$(CONFIG_HAVE_GPIO_SPI) += stm32f4/spi.c
+src-$(CONFIG_USBSERIAL) += stm32f4/usbfs.c generic/usb_cdc.c
 src-$(CONFIG_SERIAL) += stm32f4/serial.c generic/serial_irq.c
 
 # Add assembler build rules
@@ -50,6 +51,13 @@ $(OUT)klipper.bin: $(OUT)klipper.elf
 	@echo "  Creating hex file $@"
 	$(Q)$(OBJCOPY) -O binary $< $@
 
+FLASH_TYPE-$(CONFIG_MACH_STM32F1xx) := stm32f1
+FLASH_TYPE-$(CONFIG_MACH_STM32F4xx) := stm32f4
+
 flash: $(OUT)klipper.bin
+	@echo "  Flashing $< to $(FLASH_DEVICE)"
+	$(Q)$(PYTHON) ./scripts/flash_usb.py -t $(FLASH_TYPE-y) -d "$(FLASH_DEVICE)" $(if $(NOSUDO),--no-sudo) $(OUT)klipper.bin
+
+serialflash: $(OUT)klipper.bin
 	@echo "  Flashing $< to $(FLASH_DEVICE) via stm32flash"
 	$(Q)stm32flash -w $< -v -g 0 $(FLASH_DEVICE)
diff --git a/src/stm32f4/main.c b/src/stm32f4/main.c
index b3069cc9..4f4867a6 100644
--- a/src/stm32f4/main.c
+++ b/src/stm32f4/main.c
@@ -38,6 +38,8 @@ DECL_COMMAND_FLAGS(command_reset, HF_IN_SHUTDOWN, "reset");
 int
 main(void)
 {
+    SCB->VTOR += CONFIG_FLASH_START;
+
     clock_setup();
 
     sched_main();
diff --git a/src/stm32f4/usbfs.c b/src/stm32f4/usbfs.c
new file mode 100644
index 00000000..929ec01b
--- /dev/null
+++ b/src/stm32f4/usbfs.c
@@ -0,0 +1,307 @@
+// Hardware interface to "fullspeed USB controller" on stm32f1
+//
+// Copyright (C) 2018-2019  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <string.h> // NULL
+#include "autoconf.h" // CONFIG_STM32_FLASH_START_2000
+#include "board/armcm_timer.h" // udelay
+#include "board/gpio.h" // gpio_out_setup
+#include "board/io.h" // writeb
+#include "board/irq.h" // irq_disable
+#include "board/usb_cdc.h" // usb_notify_ep0
+#include "board/usb_cdc_ep.h" // USB_CDC_EP_BULK_IN
+#include "command.h" // DECL_CONSTANT_STR
+#include "internal.h" // GPIO
+#include "sched.h" // DECL_INIT
+
+
+/****************************************************************
+ * USB transfer memory
+ ****************************************************************/
+
+struct ep_desc {
+    uint32_t addr_tx, count_tx, addr_rx, count_rx;
+};
+
+struct ep_mem {
+    struct ep_desc ep0, ep_acm, ep_bulk_out, ep_bulk_in;
+    uint32_t ep0_tx[USB_CDC_EP0_SIZE / 2];
+    uint32_t ep0_rx[USB_CDC_EP0_SIZE / 2];
+    uint32_t ep_acm_tx[USB_CDC_EP_ACM_SIZE / 2];
+    uint32_t ep_bulk_out_rx[USB_CDC_EP_BULK_OUT_SIZE / 2];
+    uint32_t ep_bulk_in_tx[USB_CDC_EP_BULK_IN_SIZE / 2];
+};
+
+#define USB_BTABLE ((struct ep_mem *)(USB_BASE + 0x400))
+
+#define CALC_ADDR(p) (((void*)(p) - (void*)USB_BTABLE) / 2)
+#define CALC_SIZE(s) ((s) > 32 ? (DIV_ROUND_UP((s), 32) << 10) | 0x8000 \
+                      : DIV_ROUND_UP((s), 2) << 10)
+
+// Setup the transfer descriptors in dedicated usb memory
+static void
+btable_configure(void)
+{
+    USB_BTABLE->ep0.count_tx = 0;
+    USB_BTABLE->ep0.addr_tx = CALC_ADDR(USB_BTABLE->ep0_tx);
+    USB_BTABLE->ep0.count_rx = CALC_SIZE(USB_CDC_EP0_SIZE);
+    USB_BTABLE->ep0.addr_rx = CALC_ADDR(USB_BTABLE->ep0_rx);
+
+    USB_BTABLE->ep_acm.count_tx = 0;
+    USB_BTABLE->ep_acm.addr_tx = CALC_ADDR(USB_BTABLE->ep_acm_tx);
+
+    USB_BTABLE->ep_bulk_out.count_rx = CALC_SIZE(USB_CDC_EP_BULK_OUT_SIZE);
+    USB_BTABLE->ep_bulk_out.addr_rx = CALC_ADDR(USB_BTABLE->ep_bulk_out_rx);
+
+    USB_BTABLE->ep_bulk_in.count_tx = 0;
+    USB_BTABLE->ep_bulk_in.addr_tx = CALC_ADDR(USB_BTABLE->ep_bulk_in_tx);
+}
+
+// Read a packet stored in dedicated usb memory
+static void
+btable_read_packet(uint8_t *dest, uint32_t *src, int count)
+{
+    uint_fast8_t i;
+    for (i=0; i<(count/2); i++) {
+        uint32_t d = *src++;
+        *dest++ = d;
+        *dest++ = d >> 8;
+    }
+    if (count & 1)
+        *dest = *src;
+}
+
+// Write a packet to dedicated usb memory
+static void
+btable_write_packet(uint32_t *dest, const uint8_t *src, int count)
+{
+    int i;
+    for (i=0; i<(count/2); i++) {
+        uint8_t b1 = *src++, b2 = *src++;
+        *dest++ = b1 | (b2 << 8);
+    }
+    if (count & 1)
+        *dest = *src;
+}
+
+
+/****************************************************************
+ * USB endpoint register
+ ****************************************************************/
+
+#define USB_EPR ((volatile uint32_t *)USB_BASE)
+
+#define EP_BULK (0 << USB_EP0R_EP_TYPE_Pos)
+#define EP_CONTROL (1 << USB_EP0R_EP_TYPE_Pos)
+#define EP_INTERRUPT (3 << USB_EP0R_EP_TYPE_Pos)
+#define RX_STALL (1 << USB_EP0R_STAT_RX_Pos)
+#define RX_NAK (2 << USB_EP0R_STAT_RX_Pos)
+#define RX_VALID (3 << USB_EP0R_STAT_RX_Pos)
+#define TX_STALL (1 << USB_EP0R_STAT_TX_Pos)
+#define TX_NAK (2 << USB_EP0R_STAT_TX_Pos)
+#define TX_VALID (3 << USB_EP0R_STAT_TX_Pos)
+#define EPR_RWBITS (USB_EP0R_EA | USB_EP0R_EP_KIND | USB_EP0R_EP_TYPE)
+#define EPR_RWCBITS (USB_EP0R_CTR_RX | USB_EP0R_CTR_TX)
+
+static uint32_t
+set_stat_rx_bits(uint32_t epr, uint32_t bits)
+{
+    return ((epr & (EPR_RWBITS | USB_EP0R_STAT_RX_Msk)) ^ bits) | EPR_RWCBITS;
+}
+
+static uint32_t
+set_stat_tx_bits(uint32_t epr, uint32_t bits)
+{
+    return ((epr & (EPR_RWBITS | USB_EP0R_STAT_TX_Msk)) ^ bits) | EPR_RWCBITS;
+}
+
+static uint32_t
+set_stat_rxtx_bits(uint32_t epr, uint32_t bits)
+{
+    uint32_t mask = EPR_RWBITS | USB_EP0R_STAT_RX_Msk | USB_EP0R_STAT_TX_Msk;
+    return ((epr & mask) ^ bits) | EPR_RWCBITS;
+}
+
+
+/****************************************************************
+ * USB interface
+ ****************************************************************/
+
+int_fast8_t
+usb_read_bulk_out(void *data, uint_fast8_t max_len)
+{
+    uint32_t epr = USB_EPR[USB_CDC_EP_BULK_OUT];
+    if ((epr & USB_EP0R_STAT_RX_Msk) == RX_VALID)
+        // No data ready
+        return -1;
+    uint32_t count = USB_BTABLE->ep_bulk_out.count_rx & 0x3ff;
+    if (count > max_len)
+        count = max_len;
+    btable_read_packet(data, USB_BTABLE->ep_bulk_out_rx, count);
+    USB_EPR[USB_CDC_EP_BULK_OUT] = set_stat_rx_bits(epr, RX_VALID);
+    return count;
+}
+
+int_fast8_t
+usb_send_bulk_in(void *data, uint_fast8_t len)
+{
+    uint32_t epr = USB_EPR[USB_CDC_EP_BULK_IN];
+    if ((epr & USB_EP0R_STAT_TX_Msk) != TX_NAK)
+        // No buffer space available
+        return -1;
+    btable_write_packet(USB_BTABLE->ep_bulk_in_tx, data, len);
+    USB_BTABLE->ep_bulk_in.count_tx = len;
+    USB_EPR[USB_CDC_EP_BULK_IN] = set_stat_tx_bits(epr, TX_VALID);
+    return len;
+}
+
+int_fast8_t
+usb_read_ep0(void *data, uint_fast8_t max_len)
+{
+    uint32_t epr = USB_EPR[0];
+    if ((epr & USB_EP0R_STAT_RX_Msk) != RX_NAK)
+        // No data ready
+        return -1;
+    uint32_t count = USB_BTABLE->ep0.count_rx & 0x3ff;
+    if (count > max_len)
+        count = max_len;
+    btable_read_packet(data, USB_BTABLE->ep0_rx, count);
+    USB_EPR[0] = set_stat_rxtx_bits(epr, RX_VALID | TX_NAK);
+    return count;
+}
+
+int_fast8_t
+usb_read_ep0_setup(void *data, uint_fast8_t max_len)
+{
+    return usb_read_ep0(data, max_len);
+}
+
+int_fast8_t
+usb_send_ep0(const void *data, uint_fast8_t len)
+{
+    uint32_t epr = USB_EPR[0];
+    if ((epr & USB_EP0R_STAT_RX_Msk) != RX_VALID)
+        // Transfer interrupted
+        return -2;
+    if ((epr & USB_EP0R_STAT_TX_Msk) != TX_NAK)
+        // No buffer space available
+        return -1;
+    btable_write_packet(USB_BTABLE->ep0_tx, data, len);
+    USB_BTABLE->ep0.count_tx = len;
+    USB_EPR[0] = set_stat_tx_bits(epr, TX_VALID);
+    return len;
+}
+
+void
+usb_stall_ep0(void)
+{
+    USB_EPR[0] = set_stat_rxtx_bits(USB_EPR[0], RX_STALL | TX_STALL);
+}
+
+static uint8_t set_address;
+
+void
+usb_set_address(uint_fast8_t addr)
+{
+    writeb(&set_address, addr | USB_DADDR_EF);
+    usb_send_ep0(NULL, 0);
+}
+
+void
+usb_set_configure(void)
+{
+}
+
+void
+usb_request_bootloader(void)
+{
+    if (!CONFIG_STM32_FLASH_START_2000)
+        return;
+    // Enter "stm32duino" bootloader
+    irq_disable();
+    RCC->APB1ENR |= RCC_APB1ENR_PWREN | RCC_APB1ENR_BKPEN;
+    PWR->CR |= PWR_CR_DBP;
+    BKP->DR10 = 0x01;
+    PWR->CR &=~ PWR_CR_DBP;
+    NVIC_SystemReset();
+}
+
+
+/****************************************************************
+ * Setup and interrupts
+ ****************************************************************/
+
+DECL_CONSTANT_STR("RESERVE_PINS_USB", "PA11,PA12");
+
+// Initialize the usb controller
+void
+usb_init(void)
+{
+    // Pull the D+ pin low briefly to signal a new connection
+    gpio_out_setup(GPIO('A', 12), 0);
+    udelay(5000);
+    gpio_in_setup(GPIO('A', 12), 0);
+
+    // Setup USB packet memory
+    btable_configure();
+
+    // Enable USB clock
+    enable_pclock(USB_BASE);
+
+    // Reset usb controller and enable interrupts
+    USB->CNTR = USB_CNTR_FRES;
+    USB->BTABLE = 0;
+    USB->DADDR = 0;
+    USB->CNTR = USB_CNTR_RESETM;
+    USB->ISTR = 0;
+    NVIC_SetPriority(USB_LP_CAN1_RX0_IRQn, 1);
+    NVIC_EnableIRQ(USB_LP_CAN1_RX0_IRQn);
+}
+DECL_INIT(usb_init);
+
+// Configure interface after a USB reset event
+static void
+usb_reset(void)
+{
+    USB_EPR[0] = 0 | EP_CONTROL | RX_VALID | TX_NAK;
+    USB_EPR[USB_CDC_EP_ACM] = USB_CDC_EP_ACM | EP_INTERRUPT | RX_NAK | TX_NAK;
+    USB_EPR[USB_CDC_EP_BULK_OUT] = (USB_CDC_EP_BULK_OUT | EP_BULK
+                                    | RX_VALID | TX_NAK);
+    USB_EPR[USB_CDC_EP_BULK_IN] = (USB_CDC_EP_BULK_IN | EP_BULK
+                                   | RX_NAK | TX_NAK);
+
+    USB->CNTR = USB_CNTR_CTRM | USB_CNTR_RESETM;
+    USB->DADDR = USB_DADDR_EF;
+}
+
+// Main irq handler
+void __visible
+USB_LP_CAN1_RX0_IRQHandler(void)
+{
+    uint32_t istr = USB->ISTR;
+    if (istr & USB_ISTR_CTR) {
+        // Endpoint activity
+        uint32_t ep = istr & USB_ISTR_EP_ID;
+        uint32_t epr = USB_EPR[ep];
+        USB_EPR[ep] = epr & EPR_RWBITS;
+        if (ep == 0) {
+            usb_notify_ep0();
+            if (epr & USB_EP_CTR_TX && set_address) {
+                // Apply address after last "in" message transmitted
+                USB->DADDR = set_address;
+                set_address = 0;
+            }
+        } else if (ep == USB_CDC_EP_BULK_OUT) {
+            usb_notify_bulk_out();
+        } else if (ep == USB_CDC_EP_BULK_IN) {
+            usb_notify_bulk_in();
+        }
+    }
+    if (istr & USB_ISTR_RESET) {
+        // USB Reset
+        USB->ISTR = (uint16_t)~USB_ISTR_RESET;
+        usb_reset();
+    }
+}