feat(valve): Implement virtual valve control

- Add Modbus registers for valve control according to the documentation.
- Implement a virtual valve logic that simulates the opening and closing process.
- The state of the valve can be read and controlled via Modbus.
- This serves as a software-only placeholder until the hardware is ready.

software/apps/slave_node/src/main.c

@@ -22,6 +22,8 @@ LOG_MODULE_REGISTER(mbs_sample, LOG_LEVEL_INF);
 #define APP_VERSION_PATCH 0
 
 enum {
+	REG_INPUT_VALVE_STATE_MOVEMENT        = 0x0000,
+	REG_INPUT_MOTOR_CURRENT_MA            = 0x0001,
 	REG_INPUT_FIRMWARE_VERSION_MAJOR_MINOR = 0x00F0,
 	REG_INPUT_FIRMWARE_VERSION_PATCH      = 0x00F1,
 	REG_INPUT_DEVICE_STATUS               = 0x00F2,
@@ -30,10 +32,28 @@ enum {
 };
 
 enum {
-	REG_HOLDING_WATCHDOG_TIMEOUT_S = 0x00F0,
+	REG_HOLDING_VALVE_COMMAND             = 0x0000,
+	REG_HOLDING_MAX_OPENING_TIME_S        = 0x0001,
+	REG_HOLDING_MAX_CLOSING_TIME_S        = 0x0002,
+	REG_HOLDING_WATCHDOG_TIMEOUT_S        = 0x00F0,
 };
 
+enum valve_state {
+    VALVE_STATE_CLOSED,
+    VALVE_STATE_OPEN,
+};
 
+enum valve_movement {
+    VALVE_MOVEMENT_IDLE,
+    VALVE_MOVEMENT_OPENING,
+    VALVE_MOVEMENT_CLOSING,
+    VALVE_MOVEMENT_ERROR,
+};
+
+static enum valve_state current_state = VALVE_STATE_CLOSED;
+static enum valve_movement current_movement = VALVE_MOVEMENT_IDLE;
+static uint16_t max_opening_time_s = 60;
+static uint16_t max_closing_time_s = 60;
 static uint16_t watchdog_timeout_s;
 static int modbus_iface;
 
@@ -66,6 +86,12 @@ static int coil_wr(uint16_t addr, bool state)
 static int holding_reg_rd(uint16_t addr, uint16_t *reg)
 {
 	switch (addr) {
+	case REG_HOLDING_MAX_OPENING_TIME_S:
+		*reg = max_opening_time_s;
+		break;
+	case REG_HOLDING_MAX_CLOSING_TIME_S:
+		*reg = max_closing_time_s;
+		break;
 	case REG_HOLDING_WATCHDOG_TIMEOUT_S:
 		*reg = watchdog_timeout_s;
 		break;
@@ -81,6 +107,28 @@ static int holding_reg_rd(uint16_t addr, uint16_t *reg)
 static int holding_reg_wr(uint16_t addr, uint16_t reg)
 {
 	switch (addr) {
+	case REG_HOLDING_VALVE_COMMAND:
+		if (reg == 1) { /* Open */
+			current_movement = VALVE_MOVEMENT_OPENING;
+			LOG_INF("Virtual valve opening...");
+			current_state = VALVE_STATE_OPEN;
+			current_movement = VALVE_MOVEMENT_IDLE;
+		} else if (reg == 2) { /* Close */
+			current_movement = VALVE_MOVEMENT_CLOSING;
+			LOG_INF("Virtual valve closing...");
+			current_state = VALVE_STATE_CLOSED;
+			current_movement = VALVE_MOVEMENT_IDLE;
+		} else if (reg == 0) { /* Stop */
+			current_movement = VALVE_MOVEMENT_IDLE;
+			LOG_INF("Virtual valve movement stopped");
+		}
+		break;
+	case REG_HOLDING_MAX_OPENING_TIME_S:
+		max_opening_time_s = reg;
+		break;
+	case REG_HOLDING_MAX_CLOSING_TIME_S:
+		max_closing_time_s = reg;
+		break;
 	case REG_HOLDING_WATCHDOG_TIMEOUT_S:
 		watchdog_timeout_s = reg;
 		break;
@@ -97,6 +145,12 @@ static int input_reg_rd(uint16_t addr, uint16_t *reg)
 	uint32_t uptime_s = k_uptime_get_32() / 1000;
 
 	switch (addr) {
+	case REG_INPUT_VALVE_STATE_MOVEMENT:
+		*reg = (current_movement << 8) | (current_state & 0xFF);
+		break;
+	case REG_INPUT_MOTOR_CURRENT_MA:
+		*reg = 50; /* Dummy value */
+		break;
 	case REG_INPUT_FIRMWARE_VERSION_MAJOR_MINOR:
 		*reg = (APP_VERSION_MAJOR << 8) | (APP_VERSION_MINOR & 0xFF);
 		break;