SCORE Time Synchronization Documentation#

This documentation describes the SCORE (Scalable Core for Automotive Real-time Environments) Time Synchronization system, which provides high-precision time synchronization for automotive applications using gPTP (IEEE 802.1AS) and NTP.

Overview #

SCORE Time Synchronization is a safety-critical time synchronization daemon (tsyncd) and client library (libscore_time) designed for automotive systems. It provides:

Vehicle Time: High-precision synchronized time using gPTP (IEEE 802.1AS) over Ethernet
Absolute Time: UTC/wall-clock time from GNSS, NTP, or kernel RTC
Lock-free IPC: Shared memory communication using seqlock protocol for zero-copy reads
AUTOSAR Compliance: Designed for ASIL QM level with safety qualifiers
Multi-platform: Supports Linux and QNX operating systems

Key Features #

Time Synchronization

gPTP (IEEE 802.1AS) slave implementation for vehicle time
NTP client for absolute time synchronization
Support for external time sources (GNSS)
Automatic fallback and error recovery

Performance & Safety

Lock-free shared memory IPC using seqlock protocol
Zero-copy time reads for clients
ASIL QM compliance with safety qualifiers
Sub-microsecond precision for vehicle time

Platform Support

Linux with PTP Hardware Clock (PHC) support
QNX with BPF packet capture
Bazel build system for reproducible builds

Project Layout #

The SCORE Time Synchronization project includes the following structure:

src/common/: Shared IPC and utility code - include/score_time/ipc/: Shared memory structures (SharedState, ShmRegion) - include/score_time/utils/: Utilities (PthreadLockGuard, time functions, parsers)
src/tsyncd/: Time synchronization daemon implementation - engine/: Core synchronization engine and state machine - platform/: Platform-specific code (Linux, QNX) - protocol/: gPTP and NTP protocol implementations
src/libscore_time/: Client library for reading synchronized time
tests/: Unit and integration tests
docs/: API documentation and architecture diagrams

Quick Start #

Building the Project

To build all components:

# Build all components
bazel build //src/...

# Build tsyncd daemon only
bazel build //src/tsyncd:tsyncd

# Build client library
bazel build //src/libscore_time:score_time

# Run all tests
bazel test //tests/...

Running tsyncd Daemon

# Run with default configuration
sudo bazel run //src/tsyncd:tsyncd -- --iface eth0

# Run with custom configuration file
sudo bazel run //src/tsyncd:tsyncd -- --config /path/to/config.ini

Using Client Library

#include "score_time/ipc/shared_state.hpp"
#include "score_time/ipc/shm_region.hpp"

// Open shared memory
score_time::ipc::ShmRegion shm;
shm.Open("/score_time_vehicle_time", sizeof(score_time::ipc::SharedState), false);

auto* state = static_cast<score_time::ipc::SharedState*>(shm.Addr());

// Read vehicle time
std::int64_t base_ns, mono_ns;
score_time::AccuracyQualifier acc;
score_time::TimePointQualifier tpq;

if (score_time::ipc::ReadVehicle(*state, base_ns, mono_ns, acc, tpq)) {
    // Use synchronized time
}