Jump to system memory boot from user application

Fixes stm32duino#706

Signed-off-by: Frederic Pillon <[email protected]>

Author: fpistm

cores/arduino/stm32/backup.h

@@ -58,6 +58,13 @@ extern "C" {
 #endif /* HID_MAGIC_NUMBER_BKP_VALUE */
 #endif /* BL_HID */
 
+#if !defined(SYSBL_MAGIC_NUMBER_BKP_INDEX)
+#define SYSBL_MAGIC_NUMBER_BKP_INDEX LL_RTC_BKP_DR2
+#endif /* SYSBL_MAGIC_NUMBER_BKP_INDEX */
+#ifndef SYSBL_MAGIC_NUMBER_BKP_VALUE
+#define SYSBL_MAGIC_NUMBER_BKP_VALUE 0x515B
+#endif /* SYSBL_MAGIC_NUMBER_BKP_VALUE */
+
 /* Exported functions ------------------------------------------------------- */
 static inline void resetBackupDomain(void)
 {

cores/arduino/stm32/bootloader.c

@@ -1,7 +1,7 @@
 #include "bootloader.h"
-
 #include "stm32_def.h"
 #include "backup.h"
+#include "usbd_if.h"
 
 #ifdef BL_LEGACY_LEAF
 void dtr_togglingHook(uint8_t *buf, uint32_t *len)
@@ -37,3 +37,60 @@ void dtr_togglingHook(uint8_t *buf, uint32_t *len)
   }
 }
 #endif /* BL_HID */
+
+/* Request to jump to system memory boot */
+void jumpToBootloaderRequested(void)
+{
+  enableBackupDomain();
+  setBackupRegister(SYSBL_MAGIC_NUMBER_BKP_INDEX, SYSBL_MAGIC_NUMBER_BKP_VALUE);
+  NVIC_SystemReset();
+}
+
+/* Jump to system memory boot from user application */
+void jumpToBootloader(void)
+{
+  enableBackupDomain();
+  if (getBackupRegister(SYSBL_MAGIC_NUMBER_BKP_INDEX) == SYSBL_MAGIC_NUMBER_BKP_VALUE) {
+    setBackupRegister(SYSBL_MAGIC_NUMBER_BKP_INDEX, 0);
+
+#ifdef USBCON
+    USBD_reenumerate();
+#endif
+    void (*sysMemBootJump)(void);
+
+    /**
+     * Get system memory address
+     *
+     * Available in AN2606 document:
+     * Table 116. Bootloader device-dependent parameters
+     */
+    volatile uint32_t sysMem_addr = 0x1FFF0000;
+
+    /* Remap system Flash memory at address 0x00000000 */
+    __HAL_SYSCFG_REMAPMEMORY_SYSTEMFLASH();
+
+    /**
+     * Set jump memory location for system memory
+     * Use address with 4 bytes offset which specifies jump location
+     * where program starts
+     */
+    sysMemBootJump = (void (*)(void))(*((uint32_t *)(sysMem_addr + 4)));
+
+    /**
+     * Set main stack pointer.
+     * This step must be done last otherwise local variables in this function
+     * don't have proper value since stack pointer is located on different position
+     *
+     * Set direct address location which specifies stack pointer in SRAM location
+     */
+    __set_MSP(*(uint32_t *)sysMem_addr);
+
+    /**
+     * Jump to set location
+     * This will start system memory execution
+     */
+    sysMemBootJump();
+
+    while (1);
+  }
+}

cores/arduino/stm32/bootloader.h

@@ -19,6 +19,12 @@ extern "C" {
 void dtr_togglingHook(uint8_t *buf, uint32_t *len);
 #endif
 
+/* Request to jump to system memory boot */
+void jumpToBootloaderRequested(void);
+
+/* Jump to system memory boot from user application */
+void jumpToBootloader(void);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */

cores/arduino/stm32/hw_config.c

@@ -35,10 +35,11 @@
   *
   ******************************************************************************
   */
-#include "stm32_def.h"
+#include "bootloader.h"
+#include "dwt.h"
 #include "hw_config.h"
 #include "usbd_if.h"
-#include "dwt.h"
+#include "stm32_def.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -59,6 +60,9 @@ void hw_config_init(void)
   /* Initialize the HAL */
   HAL_Init();
 
+  /* Check if a jump to system memory boot requested */
+  jumpToBootloader();
+
   /* Configure the system clock */
   SystemClock_Config();
 

cores/arduino/stm32/usb/cdc/usbd_cdc_if.c

@@ -168,6 +168,9 @@ static int8_t USBD_CDC_Control(uint8_t cmd, uint8_t *pbuf, uint16_t length)
       linecoding.format     = pbuf[4];
       linecoding.paritytype = pbuf[5];
       linecoding.datatype   = pbuf[6];
+      if (linecoding.bitrate == 1200) {
+        jumpToBootloaderRequested();
+      }
       break;
 
     case CDC_GET_LINE_CODING: