TrySpace Component - Electrical Power System

This repository is an example Electrical Power System (EPS) component for the TrySpace environment.

Overview

Command line interface (CLI), flight software (FSW), ground software (GSW), and simulation (SIM) directories are included in this repository.

The EPS component is an I2C device with a fixed ID of 0x1E and a maximum speed of 400kHz. The EPS is a system as it includes a solar array, batteries, and power rails / switches to the space vehicle. Eight switches are available for routing to specific components. Each command sent to the device requires a CRC-8-CCITT polynomial 0x07 that is calculated over the I2C address through the end of the payload. The specific command format is as follows:

• uint8, I2C address (7-bit), 0x1E
• uint8, command
  • (0) No operation
  • (1) Get housekeeping
  • (2) Set switch OFF
  • (3) Set switch ON
• uint8, payload
  • Unused except for set switch commands
• uint8, CRC-8-CCITT polynomial 0x07

EPS telemetry is updated once per second. The housekeeping format is as follows:

• uint8, battery voltage (32V / 255 = 0.12549V per count)
• uint8, battery temperature (250C / 255 = 0.9803921568627451C per count)
• uint8, solar array voltage (32V / 255 =0.125V per count)
• uint8, solar array temperature (250C / 255 = 0.9803921568627451C per count)
• uint8, switch 0 state (0 off, 1 on, else fault)
• uint8, switch 0 voltage (32V / 255 =0.125V per count)
• uint8, switch 0 current (10A / 255 = 0.0392156862745098A per count)
• uint8, switch 1 state (0 off, 1 on, else fault)
• uint8, switch 1 voltage (32V / 255 =0.125V per count)
• uint8, switch 1 current (10A / 255 = 0.0392156862745098A per count)
• uint8, switch 2 state (0 off, 1 on, else fault)
• uint8, switch 2 voltage (32V / 255 =0.125V per count)
• uint8, switch 2 current (10A / 255 = 0.0392156862745098A per count)
• uint8, switch 3 state (0 off, 1 on, else fault)
• uint8, switch 3 voltage (32V / 255 =0.125V per count)
• uint8, switch 3 current (10A / 255 = 0.0392156862745098A per count)
• uint8, switch 4 state (0 off, 1 on, else fault)
• uint8, switch 4 voltage (32V / 255 =0.125V per count)
• uint8, switch 4 current (10A / 255 = 0.0392156862745098A per count)
• uint8, switch 5 state (0 off, 1 on, else fault)
• uint8, switch 5 voltage (32V / 255 =0.125V per count)
• uint8, switch 5 current (10A / 255 = 0.0392156862745098A per count)
• uint8, switch 6 state (0 off, 1 on, else fault)
• uint8, switch 6 voltage (32V / 255 =0.125V per count)
• uint8, switch 6 current (10A / 255 = 0.0392156862745098A per count)
• uint8, switch 7 state (0 off, 1 on, else fault)
• uint8, switch 7 voltage (32V / 255 =0.125V per count)
• uint8, switch 7 current (10A / 255 = 0.0392156862745098A per count)
• uint8, CRC-8-CCITT polynomial 0x07

Command Line Interface

The CLI can be configured to connect to either the hardware or simulation. This enables direct checkouts these without interference. Note that make cfg (tryspace_orchestrator.py) must be run at the top level tryspace-lab to produce the required ./shared/device_cfg.h.

Flight Software

The core Flight System (cFS) flight software application receives commands from the software bus. Two message IDs exist for commands:

• 0x18D0 - Commands
  • (0) No operation
  • (1) Reset counters
  • (3) Set switch OFF
  • (4) Set switch ON
• 0x18D1 - Requests
  • (0) Request telemetry

Two message IDs exist for telemetry:

• 0x08D0 - Application Housekeeping
• 0x08D1 - Component Telemetry

Ground Software

The XTCE file provided details the CCSDS Space Packet Protocol format used for commanding and telemetry.

Simulation

The simulation available is built as a library that is loaded by the tryspace-director for use. This maintains the state of the simulation and enables communication to the FSW via simulith. Similar to the CLI, the make cfg call at the top level tryspace-lab is required prior to building.