LoRa_stm8l

LoRa_stm8l

LoRa technology

LoRa adopts a star network structure, which is the simplest network structure with low latency compared to mesh network structure. In practical applications, IoT devices using the LoRa protocol wireless communication distance is more than 15 kilometers (suburban environment), battery life can reach more than 10 years, and can connect millions of wireless sensor nodes with LoRa technology gateways, an advantage that traditional network communication standards cannot achieve. The transmission distance, rate and power consumption of commonly used wireless communication methods are as follows:

model	The longest transmission distance	Maximum transmission rate	Minimum reception power consumption
Bluetooth	15m	2MB/s	6mA
WiFi	100m	54MB/s	105mA
ZigBee	75m	250KB/s	2mA
LoRa	15km	600KB/s	3mA

SX1278 chip

The SX1278 transceiver mainly uses LoRa remote modem, which is used for ultra-long-distance spread spectrum communication, has strong anti-interference and can minimize current power consumption. With Semtech's patented LoRa modulation technology, the SX1278 uses low-cost crystals and materials to obtain high sensitivity of more than -148dBm.
This design uses Anxinke's Ra-02 module. Related technical parameters can be found at https://docs.ai-thinker.com/lora.

stm8l chip

In this design, the STM8L051F3 processor is used, and the relevant technical parameters can be found at https://www.st.com/en/microcontrollers-microprocessors/stm8l051f3.html. The STM8L051F3 has five low power modes, namely Wait mode, Low-power run mode, Low-power wait mode, Active-halt mode and Halt mode.

1. Wait mode: The CPU clock stops working, but the selected module continues to work. Internal interrupt, external interrupt, or reset can cause the CPU to exit Wait mode.
2. Low-power run mode: The CPU and selected peripherals operate normally, using a low-speed oscillator (LSI or LSE). The microcontroller enters the low-power operation mode through software and can exit the mode through software or reset.
3. Low-power wait mode: Enters this mode when a wait event is executed at low power consumption. Similar to low power operation mode, but the CPU clock is stopped. This mode can be exited by reset, internal or triggered external events (external events generated by timer, serial interface, DMA) controller (DMA1) and I/O ports. When wakeup is triggered by an event, the system returns to low power operation mode.
4. Active-halt mode: The CPU and peripheral clocks stop except RTC. Can be woken by RTC interrupt, external interrupt or reset.
5. Halt mode: The CPU and peripheral clock are stopped and the device remains powered on. The RAM content is saved. Wake up by external interrupt or reset. Some peripherals also have a wake-up function from shutdown. It can be awakened within 5μs, and the wake-up time is very fast.

Operating in these 5 different modes, the operating current is shown in the table below:

model	Current
Wait mode
Low-power run mode	5.1μA
Low-power wait mode	3μA
Active-halt mode	1.3μA
Halt mode	350nA

The minimum driving current of the I/O pin of the STM8L051F3 microcontroller can reach 5μA, which is all for the low power consumption of the microcontroller.

Node design

Gateway design