OpenSpaceEGSE

Python-based EGSE application for on-ground satellite testing.

Current scope:

• CCSDS Space Packet encode/decode
• TM/TC SDLP transfer frame encode/decode
• UART byte-stream framing + parser
• TC send pipeline and TM receive pipeline
• Desktop GUI (control + monitoring)

The docs/ folder contains standards reference PDFs, including:

• space_packet_ccsds.pdf
• TM/TC SDLP related PDFs

---

1) Project Structure

OpenSpaceEGSE/
├── docs/
├── src/
│   └── openspace_egse/
│       ├── config.py
│       ├── ccsds/
│       │   ├── __init__.py
│       │   ├── space_packet.py
│       │   ├── sdlp.py
│       │   ├── sdlp_uart.py
│       │   ├── send_flow.py
│       │   ├── receive_flow.py
│       │   └── telemetry.py
│       └── gui/
│           └── app.py
├── tests/
└── pyproject.toml

---

2) Installation & Run

Requirements

• Python >= 3.11
• For GUI on Linux: python3-tk OS package must be installed

Setup

python -m pip install -e .[dev,gui]

Run GUI

openspace-egse-gui

Running on WSL in Windows

Running app on WSL in Windows may cause problems with USB com connection in the App. Here is the step by step instruction to handle it.

1. Make sure you have usbipd installed in your system

winget install usbipd

2. Check list of USB devices and search for your device

usbipd list

3. Bind the device (i.e. 1-2)

usbipd bind --busid 1-2

4. Attach the device to WSL (i.e. 1-2)

usbipd attach --wsl --busid 1-2

You can the check if the device is visible in WSL using commands:

lsusb

or

ls /dev/tty*

It may show up as /dev/ttyACM*.

Run tests

pytest

---

3) Protocol Stack Implemented

End-to-end flow:

TX (TC to OBC)

1. Build TC command payload
2. Wrap in CCSDS Space Packet (packet_type = TELECOMMAND)
3. Wrap in SDLP TC Transfer Frame
4. Wrap in UART stream envelope + SLIP escaping
5. Write to serial port

RX (TM from OBC)

1. Read UART bytes
2. SLIP de-frame + parse UART envelope
3. Decode SDLP TM frame
4. Extract CCSDS Space Packet(s)
5. Decode telemetry payload and display/update charts

---

4) CCSDS Space Packet

Implemented in src/openspace_egse/ccsds/space_packet.py.

Primary header length: 6 bytes.

Supported fields:

• version (3 bits)
• packet_type (TELEMETRY / TELECOMMAND)
• secondary_header_flag
• apid (11 bits)
• sequence_flags (2 bits)
• sequence_count (14 bits)
• data_length (len(data_field) - 1)

Validation includes APID, sequence count, payload length consistency, and bytes-like checks.

Example

from openspace_egse.ccsds import SpacePacket

packet = SpacePacket.build_tc(
		apid=100,
		sequence_count=5,
		payload=b"\x01\x02\x03",
)

raw = packet.encode()
decoded = SpacePacket.decode(raw)
assert decoded == packet

---

5) SDLP TM/TC Transfer Frames

Implemented in src/openspace_egse/ccsds/sdlp.py.

TM Transfer Frame (TmTransferFrame)

• Primary header length: 6 bytes
• Supports:
  • spacecraft_id, virtual_channel_id
  • master_channel_frame_count, virtual_channel_frame_count
  • first_header_pointer
  • ocf (optional, 4 bytes)
  • fecf (optional, 2 bytes)

TC Transfer Frame (TcTransferFrame)

• Primary header length: 5 bytes
• Supports:
  • spacecraft_id, virtual_channel_id, frame_sequence_number
  • bypass_flag, control_command_flag
  • frame length field consistency checks
  • optional fecf (2 bytes)

Both TM/TC include strict encode/decode length validations.

---

6) UART Framing (Stream Boundary Handling)

Implemented in src/openspace_egse/ccsds/sdlp_uart.py.

Important: this is a project transport envelope (not a CCSDS standard field layout).

Envelope payload (inside SLIP)

• Byte 0: frame type (1=TM, 2=TC)
• Byte 1: flags (bit0 = has_fecf)
• Bytes 2..3: SDLP frame length (uint16, big-endian)
• Remaining: encoded SDLP frame bytes

SLIP framing

• END=0xC0, ESC=0xDB
• Escapes handled with 0xDC / 0xDD
• Parser supports fragmented chunks and multiple concatenated frames

---

7) TC Command Creation & Sending

Implemented in src/openspace_egse/ccsds/send_flow.py.

Main API:

• TcCommandSender.send(command, parameter=None)
• TcSendConfig for SCID/VCID/APID settings

Built-in commands:

Command	Payload format
ping	0x01 + uint16(parameter)
set_mode	0x02 + uint8(parameter)
reset_subsystem	0x03 + uint8(parameter)
request_status	0x04

Sequence counters are incremented automatically after successful write.

Example

from openspace_egse.ccsds import TcCommandSender, TcSendConfig

sender = TcCommandSender(
		serial_port=my_serial,
		config=TcSendConfig(
				spacecraft_id=1,
				virtual_channel_id=0,
				space_packet_apid=100,
		),
)

sender.send("set_mode", 2)

---

8) TM Reception & Decoding

Implemented in src/openspace_egse/ccsds/receive_flow.py.

Main API:

• SdlpSpacePacketReceiver.process_uart_bytes(...)
• SdlpSpacePacketReceiver.process_serial_once(...)
• receive_and_print_once(...)

Behavior:

• Parses UART stream to TM/TC SDLP frames
• Extracts Space Packet(s) from frame data field
• For TM uses first_header_pointer as packet start offset
• Returns decoded SpacePacket objects with frame type context

---

9) Telemetry Payload Format (Current GUI Decoder)

Implemented in src/openspace_egse/ccsds/telemetry.py.

Current expected TM payload layout (>= 7 bytes):

Offset	Size	Meaning	Conversion
0	1	status code	mapped to text (BOOT/IDLE/NOMINAL/SAFE/FAULT)
1..2	2	temperature	signed int16 / 100 -> °C
3..4	2	voltage	uint16 / 1000 -> V
5..6	2	battery capacity	uint16 / 10 -> %

---

10) GUI Features

Implemented in src/openspace_egse/gui/app.py.

Control panel

• Serial connect/disconnect
• TC command selection + parameter input
• Send TC button
• Simulation tools:
  • single telemetry injection
  • auto simulation start/stop
  • simulation frequency toggle

Monitoring panel

• Live charts:
  • temperature
  • voltage
  • battery capacity
• State text fields:
  • status
  • latest values
  • last update time
• Clear telemetry data button

Event log

• On-screen event log
• Optional log-to-file
• Default file: logs/egse_events.log (repo-local)

---

11) Central Configuration

All runtime/configurable parameters are in:

• src/openspace_egse/config.py

This includes serial defaults, GUI timings/history, simulation waveform parameters, APIDs/SCID/VCID defaults, and event log defaults.

---

12) Extending with Your Own TC Commands

Edit src/openspace_egse/ccsds/send_flow.py:

1. Add enum value in TcCommandName
2. Add metadata in _TC_COMMAND_DEFINITIONS
3. Add payload encoder branch in build_tc_command_payload(...)

If parameter behavior changes, GUI control logic automatically adapts via tc_command_definition(...).

Tip: keep command IDs (0x01, 0x02, ...) stable and documented.

---

13) Extending with Your Own TM Telemetry

Edit src/openspace_egse/ccsds/telemetry.py:

1. Define your payload field offsets
2. Decode raw bytes into engineering units
3. Update status map if needed

Then update GUI rendering in src/openspace_egse/gui/app.py if you add new displayed fields or plots.

---

14) Notes

• This repository currently focuses on a clear, testable baseline rather than complete mission-specific protocol coverage.
• sdlp_uart.py transport envelope is intentionally simple for UART stream robustness and development velocity.
• Unit tests cover encode/decode, stream boundary handling, receive/send pipelines, and telemetry decoding.