lo-cate

A PCB and firmware project to create a simple LoRa capable device with an intergrated IMU.

PCB

The PCB was designed to be simple, power over USB and be manufactorable using basic electrical tooling.

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LoRa; Connected to the micro via SPI, the antenna connection is terminated to a U.FL SMD connector w/ track impedance matched to 50Ω
IMU; Connected to micro via SPI
Microcontroller; STM32F401RET7 w/ an 8MHz external oscillator to allow USB OTG capabilities.
USB; Mini B for communicating between the STM and external PC, 5v in fed into a 3.3v linear reg for use by all IC's
LED's; 3 RGB LED's connected to the micros power outputs for baic HMI
Buttons; Debounced using RC filter and connected to interrupt capable pins on the micro, MCU WKUP is connected to the micros sleep wakeup pin

[] Change the Programming header for the STM32 from the 1.27mm pins
[] Fix the oscillator circuit to fit into the STM32 design guidlines C19 & C18 should be calculated via C_L = 2*(C_Load - C_Stray) also R14 will need adjusting also