Add shared emulator services, waveform generation and STM32 USB boot ports

c/set-protocol/ports/stm32f407-usb-boot/boot_request.c

@@ -0,0 +1,26 @@
+#include "boot_port.h"
+#include "stm32f4xx_hal.h"
+#define REQUEST_MAGIC 0x42555342UL
+static uint32_t reset_at;
+static bool reset_pending;
+static void backup_access(void)
+{
+    __HAL_RCC_PWR_CLK_ENABLE();
+    PWR->CR |= PWR_CR_DBP;
+    __HAL_RCC_RTC_ENABLE();
+}
+bool f407_boot_requested(void)
+{
+    bool requested;
+    backup_access(); requested=RTC->BKP0R==REQUEST_MAGIC;
+    RTC->BKP0R=0; return requested;
+}
+void f407_request_boot(uint32_t now)
+{
+    backup_access(); RTC->BKP0R=REQUEST_MAGIC;
+    reset_at=now+500; reset_pending=true;
+}
+void f407_reset_poll(uint32_t now)
+{
+    if(reset_pending && (int32_t)(now-reset_at)>=0) NVIC_SystemReset();
+}