[ion] Add the ability to perform a jump-reset

ion/include/ion.h

@@ -34,7 +34,7 @@ const char * patchLevel();
 const char * fccId();
 
 /* CAUTION: This is a complete reset! */
-void reset();
+void reset(bool jump = false);
 
 // CRC32 : non xor-ed, non reversed, direct, polynomial 4C11DB7
 // Only accepts whole 32bit values

ion/src/device/Makefile

@@ -23,6 +23,7 @@ objs += $(addprefix ion/src/device/, \
   led.o\
   power.o\
   sd_card.o\
+  set_msp.o \
   swd.o \
   usb.o \
   wakeup.o \

ion/src/device/device.cpp

@@ -14,6 +14,7 @@ extern "C" {
 #include "swd.h"
 #include "usb.h"
 #include "bench/bench.h"
+#include "set_msp.h"
 
 #define USE_SD_CARD 0
 
@@ -65,10 +66,28 @@ uint32_t Ion::random() {
   return result;
 }
 
-void Ion::reset() {
+static void coreReset() {
+  // Perform a full core reset
   CM4.AIRCR()->requestReset();
 }
 
+static void jumpReset() {
+  Ion::Device::shutdown();
+  uint32_t * stackPointerAddress = reinterpret_cast<uint32_t *>(0x08000000);
+  uint32_t * resetHandlerAddress = reinterpret_cast<uint32_t *>(0x08000004);
+  set_msp(*stackPointerAddress);
+  void (*ResetHandler)(void) = (void (*)())(*resetHandlerAddress);
+  ResetHandler();
+}
+
+void Ion::reset(bool jump) {
+  if (jump) {
+    jumpReset();
+  } else {
+    coreReset();
+  }
+}
+
 static inline char hex(uint8_t d) {
   if (d > 9) {
     return 'A'+d-10;

ion/src/device/set_msp.h

@@ -0,0 +1,8 @@
+#ifndef ION_DEVICE_SETMSP_H
+#define ION_DEVICE_SETMSP_H
+
+#include <stdint.h>
+
+extern "C" void set_msp(uint32_t address);
+
+#endif

ion/src/device/set_msp.s

@@ -0,0 +1,10 @@
+.syntax unified
+
+.section .text
+.align 2
+.thumb
+.global set_msp
+set_msp:
+  msr msp, r0
+  bx lr
+.type set_msp, function