diff --git a/board/bootstub.c b/board/bootstub.c
index 1541a31d..a3172123 100644
--- a/board/bootstub.c
+++ b/board/bootstub.c
@@ -17,7 +17,7 @@
 
 #include "obj/cert.h"
 #include "obj/gitversion.h"
-#include "spi_flasher.h"
+#include "flasher.h"
 
 void __initialize_hardware_early(void) {
   early_initialization();
diff --git a/board/spi_flasher.h b/board/flasher.h
similarity index 85%
rename from board/spi_flasher.h
rename to board/flasher.h
index cbc1c428..2d3f90e4 100644
--- a/board/spi_flasher.h
+++ b/board/flasher.h
@@ -1,6 +1,6 @@
 // flasher state variables
 uint32_t *prog_ptr = NULL;
-int unlocked = 0;
+bool unlocked = false;
 
 #ifdef uart_ring
 void debug_ring_callback(uart_ring *ring) {}
@@ -26,23 +26,18 @@ int usb_cb_control_msg(USB_Setup_TypeDef *setup, uint8_t *resp, bool hardwired)
       break;
     // **** 0xb1: unlock flash
     case 0xb1:
-      if (FLASH->CR & FLASH_CR_LOCK) {
-        FLASH->KEYR = 0x45670123;
-        FLASH->KEYR = 0xCDEF89AB;
+      if (flash_is_locked()) {
+        flash_unlock();
         resp[1] = 0xff;
       }
       current_board->set_led(LED_GREEN, 1);
-      unlocked = 1;
-      prog_ptr = (uint32_t *)0x8004000;
+      unlocked = true;
+      prog_ptr = (uint32_t *)APP_START_ADDRESS;
       break;
     // **** 0xb2: erase sector
     case 0xb2:
       sec = setup->b.wValue.w;
-      // don't erase the bootloader
-      if (sec != 0 && sec < 12 && unlocked) {
-        FLASH->CR = (sec << 3) | FLASH_CR_SER;
-        FLASH->CR |= FLASH_CR_STRT;
-        while (FLASH->SR & FLASH_SR_BSY);
+      if (flash_erase_sector(sec, unlocked)) {
         resp[1] = 0xff;
       }
       break;
@@ -51,7 +46,7 @@ int usb_cb_control_msg(USB_Setup_TypeDef *setup, uint8_t *resp, bool hardwired)
       #ifdef STM32F4
         // addresses are OTP
         if (setup->b.wValue.w == 1) {
-          memcpy(resp, (void *)0x1fff79c0, 0x10);
+          memcpy(resp, (void *)DEVICE_SERIAL_NUMBER_ADDRESS, 0x10);
           resp_len = 0x10;
         } else {
           get_provision_chunk(resp);
@@ -122,11 +117,7 @@ void usb_cb_ep2_out(void *usbdata, int len, bool hardwired) {
   UNUSED(hardwired);
   current_board->set_led(LED_RED, 0);
   for (int i = 0; i < len/4; i++) {
-    // program byte 1
-    FLASH->CR = FLASH_CR_PSIZE_1 | FLASH_CR_PG;
-
-    *prog_ptr = *(uint32_t*)(usbdata+(i*4));
-    while (FLASH->SR & FLASH_SR_BSY);
+    flash_write_word(prog_ptr, *(uint32_t*)(usbdata+(i*4)));
 
     //*(uint64_t*)(&spi_tx_buf[0x30+(i*4)]) = *prog_ptr;
     prog_ptr++;
@@ -278,10 +269,7 @@ void soft_flasher_start(void) {
 
   enter_bootloader_mode = 0;
 
-  RCC->AHB1ENR |= RCC_AHB1ENR_DMA2EN;
-  RCC->APB2ENR |= RCC_APB2ENR_SPI1EN;
-  RCC->AHB2ENR |= RCC_AHB2ENR_OTGFSEN;
-  RCC->APB1ENR |= RCC_APB1ENR_USART2EN;
+  flasher_peripherals_init();
 
 // pedal has the canloader
 #ifdef PEDAL
@@ -297,23 +285,8 @@ void soft_flasher_start(void) {
   llcan_init(CAN1);
 #endif
 
-  // A4,A5,A6,A7: setup SPI
-  set_gpio_alternate(GPIOA, 4, GPIO_AF5_SPI1);
-  set_gpio_alternate(GPIOA, 5, GPIO_AF5_SPI1);
-  set_gpio_alternate(GPIOA, 6, GPIO_AF5_SPI1);
-  set_gpio_alternate(GPIOA, 7, GPIO_AF5_SPI1);
-
-  // A2,A3: USART 2 for debugging
-  set_gpio_alternate(GPIOA, 2, GPIO_AF7_USART2);
-  set_gpio_alternate(GPIOA, 3, GPIO_AF7_USART2);
-
-  // A11,A12: USB
-  set_gpio_alternate(GPIOA, 11, GPIO_AF10_OTG_FS);
-  set_gpio_alternate(GPIOA, 12, GPIO_AF10_OTG_FS);
-  GPIOA->OSPEEDR = GPIO_OSPEEDER_OSPEEDR11 | GPIO_OSPEEDER_OSPEEDR12;
-
-  // flasher
-  //spi_init();
+  gpio_usart2_init();
+  gpio_usb_init();
 
   // enable USB
   usb_init();
diff --git a/board/stm32fx/llflash.h b/board/stm32fx/llflash.h
new file mode 100644
index 00000000..7ce5a25f
--- /dev/null
+++ b/board/stm32fx/llflash.h
@@ -0,0 +1,26 @@
+bool flash_is_locked(void) {
+  return (FLASH->CR & FLASH_CR_LOCK);
+}
+
+void flash_unlock(void) {
+  FLASH->KEYR = 0x45670123;
+  FLASH->KEYR = 0xCDEF89AB;
+}
+
+bool flash_erase_sector(uint8_t sector, bool unlocked) {
+  // don't erase the bootloader(sector 0)
+  if (sector != 0 && sector < 12 && unlocked) {
+    FLASH->CR = (sector << 3) | FLASH_CR_SER;
+    FLASH->CR |= FLASH_CR_STRT;
+    while (FLASH->SR & FLASH_SR_BSY);
+    return true;
+  }
+  return false;
+}
+
+void flash_write_word(void *prog_ptr, uint32_t data) {
+  uint32_t *pp = prog_ptr;
+  FLASH->CR = FLASH_CR_PSIZE_1 | FLASH_CR_PG;
+  *pp = data;
+  while (FLASH->SR & FLASH_SR_BSY);
+}
diff --git a/board/stm32fx/peripherals.h b/board/stm32fx/peripherals.h
index 9522ad3d..603054fe 100644
--- a/board/stm32fx/peripherals.h
+++ b/board/stm32fx/peripherals.h
@@ -1,3 +1,16 @@
+void gpio_usb_init(void) {
+  // A11,A12: USB
+  set_gpio_alternate(GPIOA, 11, GPIO_AF10_OTG_FS);
+  set_gpio_alternate(GPIOA, 12, GPIO_AF10_OTG_FS);
+  GPIOA->OSPEEDR = GPIO_OSPEEDER_OSPEEDR11 | GPIO_OSPEEDER_OSPEEDR12;
+}
+
+void gpio_usart2_init(void) {
+  // A2,A3: USART 2 for debugging
+  set_gpio_alternate(GPIOA, 2, GPIO_AF7_USART2);
+  set_gpio_alternate(GPIOA, 3, GPIO_AF7_USART2);
+}
+
 // Common GPIO initialization
 void common_init_gpio(void){
   // TODO: Is this block actually doing something???
@@ -12,10 +25,7 @@ void common_init_gpio(void){
   // C2: Voltage sense line
   set_gpio_mode(GPIOC, 2, MODE_ANALOG);
 
-  // A11,A12: USB
-  set_gpio_alternate(GPIOA, 11, GPIO_AF10_OTG_FS);
-  set_gpio_alternate(GPIOA, 12, GPIO_AF10_OTG_FS);
-  GPIOA->OSPEEDR = GPIO_OSPEEDER_OSPEEDR11 | GPIO_OSPEEDER_OSPEEDR12;
+  gpio_usb_init();
 
   // A9,A10: USART 1 for talking to the GPS
   set_gpio_alternate(GPIOA, 9, GPIO_AF7_USART1);
@@ -31,6 +41,13 @@ void common_init_gpio(void){
   #endif
 }
 
+void flasher_peripherals_init(void) {
+  RCC->AHB1ENR |= RCC_AHB1ENR_DMA2EN;
+  RCC->APB2ENR |= RCC_APB2ENR_SPI1EN;
+  RCC->AHB2ENR |= RCC_AHB2ENR_OTGFSEN;
+  RCC->APB1ENR |= RCC_APB1ENR_USART2EN;
+}
+
 // Peripheral initialization
 void peripherals_init(void){
   // enable GPIOB, UART2, CAN, USB clock
diff --git a/board/stm32fx/stm32fx_config.h b/board/stm32fx/stm32fx_config.h
index 8bcbfa32..bdb70a62 100644
--- a/board/stm32fx/stm32fx_config.h
+++ b/board/stm32fx/stm32fx_config.h
@@ -67,7 +67,9 @@
   #include "stm32fx/lluart.h"
 #endif
 
-#ifndef BOOTSTUB
+#ifdef BOOTSTUB
+  #include "stm32fx/llflash.h"
+#else
   #include "stm32fx/llcan.h"
 #endif