diff --git a/Makefile.bootloader b/Makefile.bootloader
index 86ae89a48..5ac30ff27 100644
--- a/Makefile.bootloader
+++ b/Makefile.bootloader
@@ -50,12 +50,7 @@ OBJ_MP += $(addprefix $(BUILD_MP)/,\
 	stmhal/hal/f4/src/stm32f4xx_ll_sdmmc.o \
 	stmhal/hal/f4/src/stm32f4xx_ll_usb.o \
 	\
-	py/mpstate.o \
-	py/nlrthumb.o \
-	\
-	stmhal/pendsv.o \
 	stmhal/startup_stm32.o \
-	stmhal/systick.o \
 	)
 
 # OBJ micropython/
diff --git a/Makefile.loader b/Makefile.loader
index 73feefbed..c4e38230d 100644
--- a/Makefile.loader
+++ b/Makefile.loader
@@ -50,12 +50,7 @@ OBJ_MP += $(addprefix $(BUILD_MP)/,\
 	stmhal/hal/f4/src/stm32f4xx_ll_sdmmc.o \
 	stmhal/hal/f4/src/stm32f4xx_ll_usb.o \
 	\
-	py/mpstate.o \
-	py/nlrthumb.o \
-	\
-	stmhal/pendsv.o \
 	stmhal/startup_stm32.o \
-	stmhal/systick.o \
 	)
 
 # OBJ micropython/
diff --git a/micropython/bootloader/main.c b/micropython/bootloader/main.c
index 9d38fb153..77b9a07f4 100644
--- a/micropython/bootloader/main.c
+++ b/micropython/bootloader/main.c
@@ -16,7 +16,8 @@
 #define BOOTLOADER_PRINT(X)   do { display_print(X, -1);      display_print_out(BOOTLOADER_FGCOLOR, BOOTLOADER_BGCOLOR); } while(0)
 #define BOOTLOADER_PRINTLN(X) do { display_print(X "\n", -1); display_print_out(BOOTLOADER_FGCOLOR, BOOTLOADER_BGCOLOR); } while(0)
 
-void mp_hal_stdout_tx_str(const char *str) {
+void pendsv_isr_handler(void) {
+    __fatal_error("pendsv");
 }
 
 void periph_init(void)
diff --git a/micropython/loader/main.c b/micropython/loader/main.c
index a69f55bc2..f0103bf59 100644
--- a/micropython/loader/main.c
+++ b/micropython/loader/main.c
@@ -3,7 +3,10 @@
 #include "common.h"
 #include "display.h"
 
-void mp_hal_stdout_tx_str(const char *str) {
+#define FIRMWARE_START   0x08020000
+
+void pendsv_isr_handler(void) {
+    __fatal_error("pendsv");
 }
 
 void periph_init(void)
diff --git a/micropython/trezorhal/stm32_it.c b/micropython/trezorhal/stm32_it.c
index fe852b202..8727ebbb3 100644
--- a/micropython/trezorhal/stm32_it.c
+++ b/micropython/trezorhal/stm32_it.c
@@ -65,14 +65,13 @@
   ******************************************************************************
   */
 
-#include <stdio.h>
-
 #include STM32_HAL_H
 
-#include "py/mphal.h"
 #include "pendsv.h"
 #include "gccollect.h"
 
+#include "display.h"
+
 #define IRQ_ENTER(irq)
 #define IRQ_EXIT(irq)
 
@@ -86,7 +85,7 @@ extern void __fatal_error(const char*);
 // More information about decoding the fault registers can be found here:
 // http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0646a/Cihdjcfc.html
 
-STATIC char *fmt_hex(uint32_t val, char *buf) {
+static char *fmt_hex(uint32_t val, char *buf) {
     const char *hexDig = "0123456789abcdef";
 
     buf[0] = hexDig[(val >> 28) & 0x0f];
@@ -102,21 +101,21 @@ STATIC char *fmt_hex(uint32_t val, char *buf) {
     return buf;
 }
 
-STATIC void print_reg(const char *label, uint32_t val) {
+static void print_reg(const char *label, uint32_t val) {
     char hexStr[9];
 
-    mp_hal_stdout_tx_str(label);
-    mp_hal_stdout_tx_str(fmt_hex(val, hexStr));
-    mp_hal_stdout_tx_str("\r\n");
+    display_print(label, -1);
+    display_print(fmt_hex(val, hexStr), -1);
+    display_print("\n", 1);
 }
 
-STATIC void print_hex_hex(const char *label, uint32_t val1, uint32_t val2) {
+static void print_hex_hex(const char *label, uint32_t val1, uint32_t val2) {
     char hex_str[9];
-    mp_hal_stdout_tx_str(label);
-    mp_hal_stdout_tx_str(fmt_hex(val1, hex_str));
-    mp_hal_stdout_tx_str("  ");
-    mp_hal_stdout_tx_str(fmt_hex(val2, hex_str));
-    mp_hal_stdout_tx_str("\r\n");
+    display_print(label, -1 );
+    display_print(fmt_hex(val1, hex_str), -1);
+    display_print("  ", 2);
+    display_print(fmt_hex(val2, hex_str), -1);
+    display_print("\n", 1);
 }
 
 // The ARMv7M Architecture manual (section B.1.5.6) says that upon entry
@@ -138,7 +137,7 @@ void HardFault_C_Handler(ExceptionRegisters_t *regs) {
     // the VCP and then block indefinitely waiting for the buffer to drain.
     // pyb_usb_flags = 0;
 
-    mp_hal_stdout_tx_str("HardFault\r\n");
+    display_print("HardFault\n", -1);
 
     print_reg("R0    ", regs->r0);
     print_reg("R1    ", regs->r1);
@@ -162,7 +161,7 @@ void HardFault_C_Handler(ExceptionRegisters_t *regs) {
     }
 
     if ((void*)&_ram_start <= (void*)regs && (void*)regs < (void*)&_ram_end) {
-        mp_hal_stdout_tx_str("Stack:\r\n");
+        display_print("Stack:\n", -1);
         uint32_t *stack_top = &_estack;
         if ((void*)regs < (void*)&_heap_end) {
             // stack not in static stack area so limit the amount we print