Description

The communications subsystem is in charge of sending the telemetry of the satellite, and receive the commands over radio. It is mounted with a Transceiver, in this case a LoRa module, that transmit the incoming SPI information to LoRa signals.

In this subsystem you will find a ESP32S3 (U1), a well known microcontroller that can be used with the Arduino Framework. It is also used in the Prototype Subsystem, making them very similar to each other. It also counts with a Lora Transceiver, the RFM95 (U2), that is controlled over SPI. Lastly there is a CAN transceiver (U6) that is used for the communication with the other subsystems.

PCB Overview

Blocks description

• U1 - Pink box: Is the microcontroller of the subsystem, the ESP32S3.
• U2 - Cyan box: LoRa module RFM95W-868S2. It is based on the chip SX1272 from Semtech.
• J2 - Green box: The ESP-Prog interface. Is used to flash the software on the microcontroller using the external programmer ESP-Prog
• U6 - Orange box: CAN transceiver. It is the SN65HVD234D. It interfaces between a Controller Area Network (CAN) controller and the physical CAN bus. It acts as a mediator, converting the digital signals from the CAN controller into the appropriate electrical signals suitable for transmission over the CAN bus, and vice versa.
• R8 - Red box: CAN optional terminantion resistors. A CAN network needs to have 120 ohms resistors on the end of the network. The very top Subsystem and the bottom subsystem of the satellite needs to be populated with 120 Ohm resistor and the solderbridge close.
• SW1, L1, L2 - Purple box: This board has 2 Leds, one is “ON” where there is power in the system, and the other is attached to IO36 of the microcontroller. The button SW1 is a reset button.