diff --git a/Makefile b/Makefile
index 100ef65..52765a4 100644
--- a/Makefile
+++ b/Makefile
@@ -47,3 +47,5 @@ dump:
 	open DUMP.s
 tty: flash
 	screen /dev/tty.SLAB_USBtoUART 115200
+dfu:
+	dfu-util -d 0483:df11 -c 1 -a 0 -s 0x08000000:leave -D main.bin
diff --git a/linker.ld b/linker.ld
index 79b7bcf..b678b36 100644
--- a/linker.ld
+++ b/linker.ld
@@ -10,7 +10,7 @@ MEMORY {
 	EXTSRAM (RWX) : ORIGIN = 0x68000000 , LENGTH = 0
 	/*Adust LENGTH to (FLASHsize - FeePROMsize) of target MCU:*/
 	/*STM32F103RBT --> 126K*/
-	FLASH (RX) : ORIGIN = 0x08000000 , LENGTH = 508K
+	FLASH (RX) : ORIGIN = 0x08000000 , LENGTH = 256K
 	/*STM32F103RET --> 508K*/
 	/*FLASH (RX) : ORIGIN = 0x08000000 , LENGTH = 508K*/
 	/*STM32F103ZET --> 508K*/
diff --git a/src/main.c b/src/main.c
index 1af9d8b..b7847f6 100644
--- a/src/main.c
+++ b/src/main.c
@@ -191,6 +191,15 @@ void drawille_task() {
 }
 
 int main() {
+	RCC->APB2ENR |= RCC_APB2ENR_IOPBEN;
+	GPIOB->CRH &= 0xFFFFF0FF;
+	GPIOB->CRH |= 0x00000300;
+	while(1) {
+		GPIOB->ODR &= 0b11111111111111111111101111111111;
+		delay(1000);
+		GPIOB->ODR |= 0b00000000000000000000010000000000;
+		delay(1000);
+	}
 
 	#ifdef DEBUG_BLDC
 		//Brushless motor auto init