# STM32F103 development board, 4G Air780E module, 5V double relay, for IoT

> Development board with STM32F103C6T6 (32-bit ARM) and 4G Air780E LTE Cat.1 bis module, for IoT projects. Includes two 5V relays controlled via PA4/PA5, flip-up Nano SIM slot, 4G antenna, network status LED and relay status LEDs. Powered at 5V via USB Type-C or KF128 terminal, programmable via SWD or USART. Standby consumption 600µA. Dimensions 62 x 72,5 mm.

- Page: https://sigmanortec.ro/en/stm32f103-development-board-4g-air780e-module-5v-double-relay-for-iot
- Price: 156.80 RON
- Availability: In stock; 1-2 zile
- Reference: 88197 · EAN: 5942890340864
- Category: Mechatronics and IoT > Sensors and Modules > GSM
- Updated: 2026-09-23
- Shop: [Sigmanortec.ro](https://sigmanortec.ro/en/llms.txt)
- Prices: RON, VAT included; prices and stock as of 2026-10-22 04:49 (Europe/Bucharest)

## Description

Integrated solution for IoT projects with 4G connectivity and external load control, based on STM32F103 and Air780E LTE Cat.1 bis module with AT firmware and low idle power consumption. Includes two 5V relays controlled from PA4 and PA5, flip-up Nano SIM slot with 4G antenna and network status LED. Simple 5V power supply via USB Type-C or KF128 terminal, easy programming via SWD or USART.
This development board represents a complete and integrated solution for IoT projects requiring 4G connectivity and control of external loads. It combines an STM32F103C6T6 microcontroller with an Air780E LTE Cat.1 bis communication module, offering a versatile solution for both rapid prototyping and industrial implementations.
The Air780E module supports 4G and is designed for energy efficiency, with a standby current consumption of only 600µA. Factory-installed, the module uses AT firmware and communicates with the STM32 via the serial port, using standard AT commands for data transmission and reception over the network. The board includes two 5V relays, which can be controlled through PA4 and PA5, allowing direct control of external devices such as lighting, fans, pumps, or other equipment.
The board integrates a flip-up type Nano SIM card slot (easy to install and remove), a dedicated 4G antenna, a blue LED indicating the Air780E network status, LEDs for relay status, a reset button, and a user-programmable button. Power can be supplied either via the Type-C port or through the KF128 terminal.
Specifications:
Microcontroller: STM32F103C6T6 based on ARM architecture, 32-bit
4G Module: Air780E LTE Cat.1 bis
Network connectivity: full 4G network
Power consumption: 600µA in standby mode
Power supply: 5 VDC via USB or KF128 terminal
Relays: 2 x 5V, controlled via PA4 and PA5
SIM Slot: Flip-up type for Nano SIM
LED Indicators: Blue for Air780E network status, LEDs for relay status
Buttons: Reset and programmable button
Programming interfaces: USART (TTL) and SWD
Accessible pins: STM32 and Air780E pins brought out
Default firmware: AT firmware on Air780E, communicates with STM32 via AT commands
Dimensions: 62 x 72.5 mm
Layout:
1. USB Type C interface
2. KF128 power terminal
3. Reset button (RST) and user-programmable button KEY (PB12)
4. Nano SIM card holder
5. Air780e module
6. Antenna
7. Blue LED for network status, it blinks intermittently after power-on and blinks faster when connected to the network
8. LED for relay status
9. Double relay, 5V
10. Common IO pins for STM32
11. Common IO pins for Air780e
12. MCU: STM32F103C6T6 (LQFP-48)
Pinout:
Connector
Pin
Role
Notes
Left
5V
5V Power
5V input, same line as USB Type-C power supply
Left
D-
USB data minus
USB data line
Left
D+
USB data plus
USB data line
Left
GND
Ground
Common reference
Left
USB_BOOT
USB boot mode
Startup mode selection related to USB, useful for programming service
Left
VDD_EXT
External logic power supply
External power line for peripherals, depending on board implementation
Left
5V
5V Power
Duplicate on header for quick access
Left
MAIN_TXD
Main UART TX
Serial line, usually to the 4G module for AT commands
Left
MAIN_RXD
Main UART RX
Serial line, paired with MAIN_TXD
Left
GND
Ground
Common reference
Left
PWRKEY
Module power control
Power on/off 4G module via PWRKEY signal
Left
GND
Ground
Common reference
Right
PA4
Relay 1 control
STM32 digital output for relay 1
Right
PA5
Relay 2 control
STM32 digital output for relay 2
Right
PA6
General IO STM32
Available pin for input/output
Right
PA7
General IO STM32
Available pin for input/output
Right
PA9
USART1 TX
Serial for debugging or external communication
Right
PA10
USART1 RX
Serial for debugging or external communication
Right
3V3
3.3V Power
For peripherals at 3.3V
Right
BOOT0
STM32 boot selection
For bootloader, useful for programming via USART
Right
3V3
3.3V Power
Duplicate on header for quick access
Right
SWD
SWDIO
Data line for SWD programming and debugging
Right
CLK
SWCLK
Clock line for SWD programming and debugging
Right
GND
Ground
Common reference
Usage:
Insert an active Nano SIM card into the flip-up slot before powering on. Connect the 4G antenna to the dedicated connector. Power the board either via the USB port or the KF128 terminal.
The factory program on the board makes the STM32 send AT commands to the Air780E to connect to the network. After a successful connection, the blue network status LED will blink at an increased rate, and the two relays will activate automatically. This is the factory program intended to test 4G connectivity.
Custom programming via USART:
To upload your own firmware via USART, use a TTL serial module (e.g., CH340). Connect the module as follows:
TTL Serial Module
Development Board
GND
TX
RX
TX
3.3V
Then place a jumper between the BOOT0 pin and 3.3V to allow firmware burning.
Custom programming via SWD:
For programming via SWD, use a Link debugger (ST Link, J-Link, etc). Connect the debugger as follows:
Link Debugger
Development Board
GND
SWCLK
DCK
SWDIO
DIO
3.3V
Package contents:
1 x STM32 Development Board with Dual Relay and Air780E 4G CAT1 Module
1 x Dedicated 4G Antenna
2 x 12-pin male headers