Talkie device with LoRa

This project is software implementation for LoRa communication device implemented with STM32F103 NUCLEO board. The main function of the device is to send and receive data in very ling ranges.

Configuration of microcontroller pins

First step was configuration of STM32 pins ind CubeMX. The following libraries will be used for the project

#include "LoRa.h"
#include "gps.h"
#include "ssd1306.h"
#include "ssd1306_tests.h"
#include "ssd1306_fonts.h"
#include <string.h>
#include <stdio.h>

I configured

• UART for GPS module
  • PA10 as receiving pin
  • PA9 as transmitting pin

// ====================== GPS SETUP ==========================
GPS_Init();

void GPS_display_status(GPS_t *gps)
{
    ssd1306_SetCursor(0, 16); // adjust position as needed

    if (gps->lock == 0)
    {
        // GPS module is connected but no fix yet
        ssd1306_WriteString("GPS: no fix", Font_11x18, White);
    }
    else if (gps->lock > 0 && gps->satelites >= 3) 
    {
        // GPS has a valid fix (3+ satellites)
        ssd1306_WriteString("GPS OK!", Font_11x18, White);
    }
    else
    {
        // if GPS string is invalid or module not responding
        ssd1306_WriteString("GPS not found!", Font_11x18, White);
    }

    ssd1306_UpdateScreen();
}

char gps_buffer[GPSBUFSIZE];

GPS_parse(gps_buffer); // this fills the gps struct

GPS_display_status(&gps);

If the GPS module hasn't found sufficient amount of satellites, it is not fixed. If 3 or more satellites are fixed GPS module data will parsed. If there are wiring errors, GPS module will not be interfaced by the controller.

• For LoRa SPI protocol is used
  • PA4 for NSS PA5 for clock
  • PA6 for MISO
  • PA7 for MOSI
  • PA8 for LoRa_RST
  • PA0 for DI0

// ====================== LORA SETUP ==========================
// configuring SPI pins for lora

lora.CS_port		= NSS_GPIO_Port;
lora.CS_pin		= NSS_Pin;
lora.reset_port		= LoRa_RST_GPIO_Port;
lora.reset_pin		= LoRa_RST_Pin;
lora.DIO0_port		= DIO0_GPIO_Port;
lora.DIO0_pin		= DIO0_Pin;
lora.hSPIx		= &hspi1;

char		send_data[200];
uint16_t	status = LoRa_init(&lora);

memset(send_data, 0, 200);

// checing status
if (status == LORA_OK)
	{
		/*	
		snprintf(send_data, sizeof(send_data), "\n\r LoRa OK! :)");
		LoRa_transmit(&lora, (uint8_t*)send_data, 120, 100);
		HAL_UART_Transmit(&huart1, (uint8_t*)send_data, 200, 200);
		*/
		ssd1306_SetCursor(16, 16);
		ssd1306_WriteString("LoRa OK!", Font_11x18, White);
		ssd1306_UpdateScreen();
		HAL_Delay(500);
	}
else if (status == LORA_NOT_FOUND)
	{
		// mcu cant communicate with lora	
		ssd1306_WriteString("LoRa not found, check wiring!", Font_11x18, White);
		ssd1306_UpdateScreen();
		HAL_Delay(500);
	}
else if (status == LORA_UNAVAILABLE)
	{
		// setup is not correct
		ssd1306_WriteString("Setup is not correct..", Font_11x18, White);
		ssd1306_UpdateScreen();
		ssd1306_UpdateScreen();
		HAL_Delay(500);

	}


lora.frequency      = 434;
lora.spredingFactor = SF_9;
lora.bandWidth      = BW_250KHz;
lora.crcRate        = CR_4_8;
lora.power          = POWER_17db;
lora.overCurrentProtection = 130;
lora.preamble       = 10;

Similarly to GPS, LoRa modules wiring and status is checked in this section.

• For OLED screen I2C protocol was used
  • PB9 for serial data line
  • PB8 for serial clock

// ======================OLED SETUP =============================

// Initialize the display
ssd1306_Init();
    
// clear the display buffer
ssd1306_Fill(Black);
    
// set cursor position and write text
ssd1306_SetCursor(16, 16);
ssd1306_WriteString("Startup...", Font_11x18, White);

// update the display
ssd1306_UpdateScreen();
HAL_Delay(500);
ssd1306_Fill(Black);

OLED is initialized, and on boot a startup screen is displayed

Additionally two push buttons are connected for control (one for scanning available data, one for sending)

• scan_Pin GPIO input with pull up resistor
• send_Pin GPIO input with pull up resistor

After this the code was generated through Cube MX.

On boot (powering)

![[Pasted image 20251129213306.png| center | 600]]

Next the wiring and setting of LoRa module are checked, in case of success we get this screen

![[Pasted image 20251129213347.png| center | 600]]

For GPS, the no fix status is displayed until the enough satellites are found for a lock.

![[Pasted image 20251129213444.png| center | 600]]