ASR-A502 GMSL Camera Time Synchronization Solution Introduction

Technical documentation for implementing high-precision GMSL camera time synchronization on the ASR-A502 platform.

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Overview

1. Background and synchronization challenges
2. Solution architecture and implementation
3. Validation and verification procedures

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Why Time Synchronization Is Critical for AMR and Robotics Systems

In multi-camera robotic systems, inaccurate timestamp alignment can significantly impact the performance of SLAM, sensor fusion, and AI-based perception workloads.

To ensure deterministic frame synchronization across multiple cameras, a hardware-assisted time synchronization mechanism is required.

Technical Challenges

• Linux system time is not synchronized with camera hardware time
• Multi-camera frame timestamp misalignment
• Timing inconsistencies introduced by the GMSL deserializer
• Requirement for precise PPS (Pulse Per Second) synchronization

Solution Architecture

The ASR-A502 platform provides a hardware-assisted synchronization framework based on:

• Intel TGPIO (Time-Aware GPIO)
• PTP Hardware Clock (/dev/ptpX)
• PPS signal generation
• Continuous synchronization calibration service

The platform currently supports two synchronization methods.

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Solution Implementation

BIOS Configuration

The following BIOS features must be enabled before using the synchronization framework:

• Enable TGPIO support
• Integrate BIOS support for:
  • INTC1023
  • INTC1024

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TGPIO Hardware Routing

Verify that the CPU TGPIO signal is correctly connected to the GMSL deserializer.

The following example uses the ASR-A502 platform.

CPU to 120-pin Connector

120-pin Connector to MAX9296A (GMSL Daughter Board)

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Verify the PTP Device and Build the Test Utility

Identify which /dev/ptpX node corresponds to the TGPIO device.

The expected result should be similar to the example below, where the TGPIO device is mapped to /dev/ptp3.

udevadm info /dev/ptp* | grep virtual

Build the testptp utility according to the kernel version in use.

Reference source:

https://github.com/intel/linux-intel-lts/tree/lts-v6.12.36-linux-250711T071314Z

Build procedure:

cd <kernel source folder>

make headers_install ARCH=x86_64
make -C tools/testing/selftests/ TARGETS=ptp

Navigate to the generated binary location:

cd tools/testing/selftests/ptp

The folder contains:

• testptp executable
• testptp.c source code

The source code also demonstrates how to control TGPIO through IOCTL interfaces.

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Time Offset Measurement

Compare the TGPIO PTP hardware clock with Linux CLOCK_REALTIME to calculate the synchronization offset.

sudo ./testptp -d /dev/ptp3 -X

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PPS Signal Generation

For hardware validation, testptp can generate a PPS waveform through TGPIO output pins.

The PPS signal should be verified using an oscilloscope.

The ASR-A502 GMSL daughter board includes two deserializer ICs.

TIME_SYNC_0 → PPS Output

Example using /dev/ptp3:

sudo ./testptp -d /dev/ptp3 -i 0 -L 0,2 -p 1000000000

• 1000000000 represents a 1-second cycle period
• Output waveform:
  • 50% high level
  • 50% low level
• The generated PPS signal is not phase-aligned with Linux system time

TIME_SYNC_1 → PPS Output

sudo ./testptp -d /dev/ptp3 -i 1 -L 1,2 -p 1000000000

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Continuous Synchronization Service

Over long operating durations, drift between Linux system time and the TGPIO PTP hardware clock may gradually increase.

For robotics and AMR applications requiring stable long-term synchronization, a continuous calibration mechanism is strongly recommended.

Intel provides a reference implementation:

RDC#785823
Precision Time Measurement Test Scripts and Timed-GPIO for Linux*
https://cdrdv2.intel.com/v1/dl/getContent/785823?explicitVersion=true

The package includes a sample utility, pps, which continuously aligns the PPS signal with Linux system time while controlling TGPIO output.

Source location:

785823_PTM_Test_Scripts_TGPIO_for_Linux_Rev_1_0/
└── Time-Aware-GPIO-Support/
    └── user-code/
        └── tgpio_pps/
            └── pps.c

Before compiling pps.c, retrieve the TSC/clock ratio and nominal core crystal clock frequency using the following command:

cpuid -1 | grep -E "(Time Stamp|TSC/clock|nominal)"

Modify the required definitions inside pps.c, then rebuild the utility.

For TIME_SYNC_0 PPS output:

sudo ./pps -d /dev/ptp1 -p 0

This service continuously aligns the generated PPS signal with Linux system time.

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Notes

• The /dev/ptpX index may vary across different hardware platforms and BIOS versions.
• PPS timing accuracy should always be validated using an oscilloscope.
• Continuous synchronization services are strongly recommended for long-duration robotics and autonomous system deployments.
• Accurate hardware time synchronization is essential for reliable SLAM, sensor fusion, and AI perception workloads in multi-camera systems.