Project Overview
A LoRaWAN environment monitoring system developed for a smart agriculture startup. Powered by the STM32L4 ultra-low-power MCU and equipped with solar panels and lithium batteries, the system achieves battery-free operation for over 3 years. It monitors critical agricultural parameters including soil moisture, temperature, ambient light, and soil pH, with data transmitted to the cloud platform via LoRaWAN.
Currently, 2,000+ sensor nodes have been deployed, covering 500+ hectares of farmland.
Core Technologies
1. Ultra-Low Power Design
Overall system average power consumption < 50uA, achieving extremely long battery life:
// STM32L4 low-power mode switching
void enter_stop_mode_2(uint32_t sleep_seconds) {
// Set RTC wake-up
HAL_RTCEx_SetWakeUpTimer_IT(&hrtc, sleep_seconds,
RTC_WAKEUPCLOCK_CK_SPRE_16BITS);
// Disable non-essential peripherals
disable_peripherals();
// Enter STOP2 mode (approximately 1.5uA)
HAL_SuspendTick();
HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFI);
HAL_ResumeTick();
// Reinitialize clock after wake-up
SystemClock_Config();
}
// Sensors powered only during measurement
void sensor_measure_cycle(void) {
// Enable sensor power
HAL_GPIO_WritePin(SENSOR_PWR_GPIO, SENSOR_PWR_PIN, GPIO_PIN_SET);
HAL_Delay(100); // Wait for stabilization
// Read data
float soil_moisture = read_soil_moisture();
float temperature = read_temperature();
float light = read_light_sensor();
// Disable sensor power
HAL_GPIO_WritePin(SENSOR_PWR_GPIO, SENSOR_PWR_PIN, GPIO_PIN_RESET);
// Send LoRaWAN packet
send_lora_packet(soil_moisture, temperature, light);
}
2. LoRaWAN Class A Communication
Using LoRaWAN Class A mode to maximize battery life:
- SF7-SF12 adaptive: Automatically adjusts based on signal strength
- ADR enabled: Automatic transmit power adjustment
- Confirmed mode: Confirmed uplink for critical data
3. Solar Power System
- Solar panel: 2W monocrystalline silicon solar panel
- Charge IC: BQ25895 intelligent charge controller
- Battery: 18650 lithium battery 3400mAh x 2
- MPPT: Maximum power point tracking
System Architecture
Solar Panel
|
+------------------------+------------------------+
| Sensor Node (STM32L4) |
| +---------+ +---------+ +---------+ +-------+ |
| | Soil | | Temp | | Light | | pH | |
| | Moisture| | | | | | | |
| +---------+ +---------+ +---------+ +-------+ |
| | |
| +------+------+ |
| | SX1262 | |
| | LoRa Module| |
| +------+------+ |
+----------------------+---------------------------+
| LoRaWAN
v
+-----------------+
| LoRaWAN Gateway |
| (RAK7268) |
+--------+--------+
| 4G / Ethernet
v
+-----------------+
| Chirpstack |
| Network Server |
+--------+--------+
|
+------------+------------+
v v v
+----------+ +----------+ +----------+
| InfluxDB | | Grafana | | Alert |
| | | | | System |
+----------+ +----------+ +----------+
Project Results
- Coverage range: Single gateway covers 3km radius
- Battery life: Verified operation exceeding 3 years
- Data accuracy: Moisture +/-3%, Temperature +/-0.3 degrees C
- Water savings: Farmers save an average of 25% on water usage
Client Testimonial
"With this system, we can precisely monitor the condition of every plot of farmland. Irrigation and fertilization are much more efficient now." — Farm Manager