EmbeddedPUS

Minimal ECSS Packet Utilisation Standard (PUS) implementation in C, designed for small-scale academic space missions.

Zero dynamic allocation, no global state, C99 with C++-compatible headers — and 100% line & branch test coverage.

Standards Compliance

• ECSS-E-ST-70-41C: Packet Utilisation Standard (PUS)

Features

Implemented Services

Service	Name	Subtypes
ST[01]	Request Verification	Acceptance, Start, Completion (success & failure), Routing failure; Progress reports must be emitted manually by the handler
ST[03]	Housekeeping	TM[3,25] HK report, TM[3,26] diagnostic report
ST[05]	Event Reporting	Info, Low/Medium/High severity
ST[17]	Test	TC[17,1] are-you-alive, TC[17,3] on-board connection test
ST[20]	Parameter Management	TC[20,1] request report, TC[20,3] set values, TM[20,2] value report

Design Principles

• Transport-agnostic — a pure PUS layer operating on the secondary header and application data; wrap its packets in a CCSDS Space Packet primary header or carry them in CCSDS SDLP TC/TM transfer frames
• No heap — all memory is caller-supplied or statically declared
• No global state — everything lives in a pus_context_t you own
• Composable — each service has its own context struct; mix and match what you need
• Portable C — no platform-specific dependencies
• C99, C++-friendly — compiles as C99; every public header is wrapped in extern "C" for direct use from C++

Project Structure

EmbeddedPUS/
├── include/ # Public API headers
├── src/ # Library source + internal headers
├── example/
│ └── obc_example.c # Minimum OBC usage example
├── tests/ # Unit tests (single file per module) + minimal framework
├── tools/
│ └── coverage_html.sh # Coverage report generator
├── docs/ # ECSS-E-ST-70-41C reference (PDF)
├── Makefile
├── LICENSE
└── README.md

Building

make # build and run tests
make example # build and run the OBC example
make clean # remove build artifacts

Testing & Coverage

make compiles and runs the full unit-test suite under a strict warning set (-Wall -Wextra -Wpedantic -Wconversion and more). Coverage is maintained at 100% of lines and branches; regenerate the report with gcovr:

sudo apt install gcovr
make coverage-html
# Prints a console summary and writes an HTML report to build/coverage/index.html

Quick Start

#include"pus.h"#include"pus_service_17.h"#include"pus_service_3.h"#include"pus_service_5.h"/* 1. Allocate contexts statically */staticpus_context_tg_pus;
staticpus_service_3_ctx_tg_s3;
/* 2. TM sink — called for every outgoing packet */staticpus_status_tuart_send(void*ud, constuint8_t*data, uint16_tlen)
{
(void)ud;
/* write data[0..len] to your UART / radio */returnPUS_STATUS_OK;
}
/* 3. HK provider — fill the housekeeping buffer on demand */staticpus_status_thk_provider(uint16_tsid, uint8_t*buf,
uint16_tcap, uint16_t*out_len, void*ud)
{
(void)sid; (void)cap; (void)ud;
buf[0] =read_temperature();
*out_len=1u;
returnPUS_STATUS_OK;
}
voidapp_init(void)
{
/* 4. Initialise */pus_config_tcfg= {0};
cfg.default_source_id=0x0001;
cfg.tm_sink=uart_send;
pus_init_with_config(&g_pus, &cfg);
/* 5. Register service handlers */pus_service_17_register_handlers(&g_pus); /* auto-respond to ping */pus_service_3_init(&g_s3);
pus_service_3_register_hk(&g_s3, 0x0001, hk_provider, NULL);
}
voidapp_on_tc_received(constuint8_t*raw, uint16_tlen)
{
/* 6. Decode, route, verify — all in one call */pus_tc_process(&g_pus, raw, len);
}
voidapp_periodic(void)
{
/* 7. Emit periodic housekeeping */pus_service_3_emit_hk(&g_pus, &g_s3, 0x0001u);
/* 8. Emit an event */pus_service_5_emit(&g_pus, PUS_5_1_EVENT_INFO, 0x0101u, NULL, 0u);
}

See example/obc_example.c for a more complete scenario covering all five services.

Memory

• Code size: ~7.8 kB .text for all services (x86-64 -O2, unstripped; varies by target and flags)
• Per-context RAM: sizeof(pus_context_t) — handler table + counters
• No heap: zero dynamic allocation; all buffers are caller-supplied

Limitations

• Single-threaded: pus_context_t is not thread-safe; protect with a mutex if used from multiple tasks
• Fixed-capacity tables: handler slots and service contexts are bounded by PUS_MAX_TC_HANDLERS, PUS_SERVICE_3_MAX_STRUCTURES, PUS_SERVICE_20_MAX_PARAMS (all overridable at compile time via -D)

References

• ECSS-E-ST-70-41C — Telemetry and Telecommand Packet Utilization, European Cooperation for Space Standardization (local copy)

License

Licensed under the Apache License 2.0. See LICENSE.