feat(lib): Introduce adc_sensor library

Adds a new `adc_sensor` library to abstract reading analog values from ADC channels. The output of this library is currently simulated.

This library is now used by the `modbus_server` to read the motor current and the main supply voltage, replacing the previous implementation. This change improves modularity by centralizing ADC-related code into a dedicated module.

The build system has been updated to include the new library.

software/include/lib/adc_sensor.h

@@ -0,0 +1,27 @@
+#ifndef ADC_SENSOR_H
+#define ADC_SENSOR_H
+
+#include <stdint.h>
+
+/**
+ * @brief Initialize the ADC sensor system
+ * 
+ * @return 0 on success, negative error code on failure
+ */
+int adc_sensor_init(void);
+
+/**
+ * @brief Get supply voltage reading in millivolts
+ * 
+ * @return Voltage in millivolts (currently simulated: 12000mV)
+ */
+uint16_t adc_sensor_get_voltage_mv(void);
+
+/**
+ * @brief Get motor current reading in milliamps
+ * 
+ * @return Current in milliamps (currently simulated: 45mA)
+ */
+uint16_t adc_sensor_get_current_ma(void);
+
+#endif /* ADC_SENSOR_H */

software/lib/CMakeLists.txt

@@ -1,3 +1,4 @@
+add_subdirectory_ifdef(CONFIG_ADC_SENSOR adc_sensor)
 add_subdirectory_ifdef(CONFIG_LIB_FWU fwu)
 add_subdirectory_ifdef(CONFIG_LIB_MODBUS_SERVER modbus_server)
 add_subdirectory_ifdef(CONFIG_LIB_VALVE valve)

software/lib/Kconfig

@@ -1,5 +1,6 @@
 menu "Irrigation system software libraries"
 
+rsource "adc_sensor/Kconfig"
 rsource "fwu/Kconfig"
 rsource "modbus_server/Kconfig"
 rsource "valve/Kconfig"

software/lib/adc_sensor/CMakeLists.txt

@@ -0,0 +1 @@
+zephyr_library_sources(adc_sensor.c)

software/lib/adc_sensor/Kconfig

@@ -0,0 +1,16 @@
+config ADC_SENSOR
+	bool "ADC sensor library"
+	default y
+	help
+	  Enable ADC sensor library for voltage and current measurements.
+
+if ADC_SENSOR
+
+config ADC_SENSOR_SIMULATED
+	bool "Use simulated ADC readings"
+	default y
+	help
+	  Use simulated values instead of real ADC readings.
+	  Voltage: 12000mV, Current: 45mA
+
+endif # ADC_SENSOR

software/lib/adc_sensor/adc_sensor.c

@@ -0,0 +1,61 @@
+#include <zephyr/kernel.h>
+#include <zephyr/logging/log.h>
+#include <lib/adc_sensor.h>
+
+LOG_MODULE_REGISTER(adc_sensor, LOG_LEVEL_INF);
+
+// Simulated values
+#define SIMULATED_VOLTAGE_MV 12000
+#define SIMULATED_CURRENT_MA 45
+
+static bool initialized = false;
+
+int adc_sensor_init(void)
+{
+    if (initialized) {
+        return 0;
+    }
+
+#ifdef CONFIG_ADC_SENSOR_SIMULATED
+    LOG_INF("ADC sensor initialized (simulated mode)");
+    LOG_INF("Simulated values: %dmV, %dmA", SIMULATED_VOLTAGE_MV, SIMULATED_CURRENT_MA);
+#else
+    // TODO: Initialize real ADC hardware
+    LOG_INF("ADC sensor initialized (real ADC mode - not yet implemented)");
+#endif
+
+    initialized = true;
+    return 0;
+}
+
+uint16_t adc_sensor_get_voltage_mv(void)
+{
+    if (!initialized) {
+        LOG_WRN("ADC sensor not initialized, calling adc_sensor_init()");
+        adc_sensor_init();
+    }
+
+#ifdef CONFIG_ADC_SENSOR_SIMULATED
+    return SIMULATED_VOLTAGE_MV;
+#else
+    // TODO: Read real ADC value for voltage
+    // For now return simulated value
+    return SIMULATED_VOLTAGE_MV;
+#endif
+}
+
+uint16_t adc_sensor_get_current_ma(void)
+{
+    if (!initialized) {
+        LOG_WRN("ADC sensor not initialized, calling adc_sensor_init()");
+        adc_sensor_init();
+    }
+
+#ifdef CONFIG_ADC_SENSOR_SIMULATED
+    return SIMULATED_CURRENT_MA;
+#else
+    // TODO: Read real ADC value for current
+    // For now return simulated value
+    return SIMULATED_CURRENT_MA;
+#endif
+}

software/lib/modbus_server/modbus_server.c

@@ -8,6 +8,7 @@
 #include <lib/modbus_server.h>
 #include <lib/valve.h>
 #include <lib/fwu.h>
+#include <lib/adc_sensor.h>
 #include <app_version.h>
 
 #include <zephyr/usb/usb_device.h>
@@ -121,7 +122,7 @@ static int input_reg_rd(uint16_t addr, uint16_t *reg)
 		*reg = (valve_get_movement() << 8) | (valve_get_state() & 0xFF);
 		break;
 	case REG_INPUT_MOTOR_CURRENT_MA:
-		*reg = valve_get_motor_current();
+		*reg = adc_sensor_get_current_ma();
 		break;
 	case REG_INPUT_UPTIME_SECONDS_LOW:
 		*reg = (uint16_t)(uptime_s & 0xFFFF);
@@ -130,7 +131,7 @@ static int input_reg_rd(uint16_t addr, uint16_t *reg)
 		*reg = (uint16_t)(uptime_s >> 16);
 		break;
 	case REG_INPUT_SUPPLY_VOLTAGE_MV:
-		*reg = 12300;
+		*reg = adc_sensor_get_voltage_mv();
 		break;
 	case REG_INPUT_FWU_LAST_CHUNK_CRC:
 		*reg = fwu_get_last_chunk_crc();
@@ -160,6 +161,13 @@ int modbus_server_init(void)
 {
 	k_timer_init(&watchdog_timer, watchdog_timer_handler, NULL);
 	
+	// Initialize ADC sensor
+	int ret = adc_sensor_init();
+	if (ret < 0) {
+		LOG_ERR("Failed to initialize ADC sensor: %d", ret);
+		return ret;
+	}
+	
 	// Load saved settings
 	uint32_t saved_baudrate = 19200;
 	uint8_t saved_unit_id = 1;