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LORA-GPS-Tracker

This page is a work in progress!

This LORA-GPS-Tracker was designed to just test three modules, which I haven't worked with yet: the RFM95 LORA module, the ESP32-S2-Mini module and the ATGM336h GPS module. All combined this device can be used as a GPS-Tracker for LORA based systems. Additionally to the modules, the board includes a 0.96" OLED display, two user buttons, a user RGB LED, a LiPo battery charger with a 16340 cell holder, and a dual LDO setup, which is very handy when it comes to deep sleeping.

Here are some specs of the board:

  • ESP32-S2-Mini
  • USB Type-C for charging the battery and flashing the ESP32
  • Dual LDO setup, which will reduce the sleep current (the main power sinks can be shut down before entering a sleep mode)
  • Power friendly OLED display
  • Dimensions are 60x43mm

The Youtube Video shows the PCB assembly process, some initial tests and some power measurements.

Connections

The RFM95 LORA module is connected via SPI, the ATGM336h GPS module is connected via UART and the OLED display is connected via I2C.

GPIO ESP32 Function Mode
GPIO1 LORA_RST Output
GPIO2 LORA_MISO Input
GPIO3 LORA_MOSI Output
GPIO4 LORA_SCK Output
GPIO5 LORA_CS Output
GPIO6 LORA_INT Input
GPIO7 LORA_DIO1 Data
GPIO8 LORA_DIO2 Data
GPIO12 Button2 Input
GPIO14 Enable LDO2 Output
GPIO15 BAT_ADC Input
GPIO16 Button1 Input
GPIO19 USB_DN Data
GPIO20 USB_DP Data
GPIO34 OLED_RST Output
GPIO35 I2C_SCL Output
GPIO36 I2C_SDA Data
GPIO37 LED_CLK Output
GPIO38 LED_SDI Data
GPIO40 GPS_PPS Input
GPIO41 GPS_RXD Input
GPIO42 GPS_TXD Output

By switching off the EN_LDO2 output, the second LDO which powers the GPS as well as LORA module, the onboard LED and the OLED display, will be shut down.

Power measurements

State Avg. current Peak current
Reading sensors 80mA 92mA
Transmitting LORA 135mA 208mA
Deep sleep 75µA 82µA

Note: The schematics in this repo have the I2C pull-up resistors connected to +3V3. It reduces the power consumption if you don't mount these resistors or if you connect them to VDD (controllable via LDO2).