Backup NV-RAM refactor (#518)

* Backup NV-RAM refactor

* More comments on BACKUP_IGNITION_SWITCH_COUNTER

firmware/hw_layer/backup_ram.cpp

@@ -0,0 +1,33 @@
+/**
+ * @file	backup_ram.cpp
+ *
+ * @date Dec 19, 2017
+ */
+
+#include "backup_ram.h"
+
+uint32_t backupRamLoad(backup_ram_e idx) {
+	switch (idx) {
+	case BACKUP_STEPPER_POS:
+		return RTCD1.rtc->BKP0R & 0xffff;
+	case BACKUP_IGNITION_SWITCH_COUNTER:
+		return (RTCD1.rtc->BKP0R >> 16) & 0xff;
+	default:
+		//scheduleMsg(logger, "Invalid backup ram idx %d", idx);
+		return 0;
+	}
+}
+
+void backupRamSave(backup_ram_e idx, uint32_t value) {
+	switch (idx) {
+	case BACKUP_STEPPER_POS:
+		RTCD1.rtc->BKP0R = (RTCD1.rtc->BKP0R & ~0x0000ffff) | (value & 0xffff);
+		break;
+	case BACKUP_IGNITION_SWITCH_COUNTER:
+		RTCD1.rtc->BKP0R = (RTCD1.rtc->BKP0R & ~0x00ff0000) | ((value & 0xff) << 16);
+		break;
+	default:
+		//scheduleMsg(logger, "Invalid backup ram idx %d, value 0x08x", idx, value);
+		break;
+	}
+}

firmware/hw_layer/backup_ram.h

@@ -0,0 +1,36 @@
+/**
+ * @file	backup_ram.cpp
+ * @brief	Non-volatile backup-RAM registers support
+ *
+ * @date Dec 19, 2017
+ */
+
+#ifndef BACKUP_RAM_H_
+#define BACKUP_RAM_H_
+
+#include "main.h"
+#include "efiGpio.h"
+
+typedef enum {
+	/**
+	 * IAC Stepper motor position, 16-bit (stored in BKP0R 0..15)
+	 * Used in stepper.cpp
+	 */
+	BACKUP_STEPPER_POS,
+	/**
+	 * Ignition switch counter, 8-bit (stored in BKP0R 16..23)
+	 * The counter stores the number of times the ignition switch is turned on. Used for prime injection pulse.
+	 * We need a protection against 'fake' ignition switch on and off (i.e. no engine started), to avoid repeated prime pulses.
+	 * So we check and update the ignition switch counter in non-volatile backup-RAM.
+	 * See startPrimeInjectionPulse() in controllers/trigger/main_trigger_callback.cpp
+	 */
+	BACKUP_IGNITION_SWITCH_COUNTER,
+} backup_ram_e;
+
+
+// load data from backup-power RTC registers (non-volatile memory)
+uint32_t backupRamLoad(backup_ram_e idx);
+// use backup-power RTC registers (non-volatile memory) to store the data
+void backupRamSave(backup_ram_e idx, uint32_t value);
+
+#endif /* BACKUP_RAM_H_ */

firmware/hw_layer/hw_layer.mk

@@ -30,5 +30,6 @@ HW_LAYER_EMS_CPP = $(HW_LAYER_EGT_CPP) \
 	$(PROJECT_DIR)/hw_layer/servo.cpp \
 	$(PROJECT_DIR)/hw_layer/io_pins.cpp \
 	$(PROJECT_DIR)/hw_layer/stm32f4/mpu_util.cpp \
-	$(PROJECT_DIR)/hw_layer/rtc_helper.cpp
+	$(PROJECT_DIR)/hw_layer/rtc_helper.cpp \
+	$(PROJECT_DIR)/hw_layer/backup_ram.cpp
 	

firmware/hw_layer/stepper.cpp

@@ -20,11 +20,11 @@ static Logging *logger;
 
 static void saveStepperPos(int pos) {
 	// use backup-power RTC registers to store the data
-	RTCD1.rtc->BKP0R = (pos + 1);
+	backupRamSave(BACKUP_STEPPER_POS, pos + 1);
 }
 
 static int loadStepperPos() {
-	return (int)RTCD1.rtc->BKP0R - 1;
+	return (int)backupRamLoad(BACKUP_STEPPER_POS) - 1;
 }
 
 static msg_t stThread(StepperMotor *motor) {

firmware/hw_layer/stepper.h

@@ -9,6 +9,7 @@
 
 #include "main.h"
 #include "efiGpio.h"
+#include "backup_ram.h"
 
 class StepperMotor {
 public: