The Complete Guide to Capturing Every Signal on Your Vehicle’s Network
If you’ve ever finished a test run only to realise the one CAN signal you needed wasn’t in your channel list, you already know why “log everything, decide later” has become the standard for serious vehicle testing. That’s exactly the problem VBOX 4 was built to solve.
This guide covers everything engineers, test technicians, and OEM data teams need to know about full CAN and CAN FD logging with VBOX 4 — how it works under the hood, what makes it different from selective CAN logging, and how to get it running on your next test.
| VBOX 4 captures a vehicle’s entire CAN bus — including CAN FD — automatically and continuously, with no need to pre-select individual channels before a test. It does this through four isolated, hardware-independent CAN ports (RL CAN, CAN, CAN FD 1, CAN FD 2), letting it record two full vehicle CAN buses simultaneously into a single, GNSS-time-synchronised .asc file. Channel selection happens after the test, in VBOX Test Suite, so nothing is ever lost to a misconfigured logger or an unplanned signal need. |
Why “Log Now, Select Later” Matters
Traditional CAN loggers force you to decide, before you drive, exactly which signals matter. That works fine when you know precisely what you’re testing for. It falls apart the moment:
- A post-test question comes up that wasn’t in the original test plan
- An anomaly appears and you need a signal you didn’t think to log
- The same test data needs to serve two different engineering teams with two different questions
- Re-running the test isn’t an option — track time, prototype availability, weather, or budget won’t allow it
Full-bus logging removes that risk entirely. VBOX 4 records every frame on the bus, unfiltered, and lets you decide afterwards what matters. Nothing is discarded at capture time, so a single test run can answer questions nobody had thought to ask yet.
What “Full CAN Logging” Actually Means on VBOX 4
Full CAN logging is the automatic, unfiltered capture of every message travelling on a vehicle’s CAN or CAN FD bus, without requiring the operator to define a channel list, DBC mapping, or trigger condition beforehand. On VBOX 4, this is a hardware-level capability, not a configuration workaround — the raw bus traffic is written to disk exactly as it appears on the wire.
That distinction matters. Some loggers claim full-bus capture but actually apply filtering or downsampling under load. VBOX 4 logs raw, timestamped CAN and CAN FD frames straight to an industry-standard .asc file, which any downstream CAN analysis tool — not just Racelogic’s own software — can open.
Inside VBOX 4’s CAN Architecture: Four Ports, Two Full Buses
This is where VBOX 4 goes further than most competitors, and it’s worth understanding the layout in detail because it directly affects how you wire and configure a test:
| Port | Purpose |
| RL CAN | Dedicated to Racelogic modules and displays (e.g. TC8 thermocouple modules, FIM03, MFD Touch display). Supports up to 32 Racelogic module channels, auto-recognised the moment they’re connected. |
| CAN | General-purpose port for input and/or output of standard CAN 2.0 frames — can transmit up to 8 user-configured CAN messages and 16 signals out to a third-party system via CAN Pass Through. |
| CAN FD 1 | Input-only port for full raw-bus logging of either CAN FD or CAN 2.0 traffic to .asc. |
| CAN FD 2 | A second, fully independent input-only port for full raw-bus logging — meaning VBOX 4 can capture two separate vehicle CAN buses at the same time. |
Because all four ports are electrically isolated from each other, you can connect to sensitive OEM prototype networks without introducing noise, ground loops, or the risk of disturbing the vehicle’s own bus behaviour — a common concern on pre-production ECUs.
The two CAN FD ports being genuinely independent is what allows VBOX 4 to do something many single-channel loggers can’t: synchronise two entirely separate CAN buses (say, powertrain and chassis) into one merged, time-aligned .asc file. No manual timestamp alignment, no separate log files to reconcile after the test.
A Quick Refresher: What Is CAN FD, and Why Does It Matter Here?
CAN FD (Flexible Data-Rate) is the modern evolution of the classic CAN bus protocol, developed to handle the data volume of today’s vehicles. Compared to classic CAN’s 8-byte payload per frame, CAN FD frames carry up to 64 bytes and transmit at significantly higher speed — which is why it’s become the standard on ADAS-equipped and electrified platforms with dozens of high-bandwidth ECUs. A logger that only supports classic CAN simply can’t see everything a modern vehicle is saying. VBOX 4’s CAN FD ports are built specifically to keep pace with this.
Every Signal, Perfectly Timestamped Against GNSS
Raw CAN capture is only half the story — the other half is timing accuracy. VBOX 4 synchronises every logged CAN and CAN FD frame against its GNSS position and speed data, so a suspension sensor reading, a brake pressure signal, or an ADAS target output can be correlated to the exact moment and location it occurred, down to the sample. This is what turns a bus log into genuinely usable engineering data rather than just a stream of hex frames with rough timestamps.
Because the bus is captured with no filtering, VBOX 4 also handles fast-changing signals cleanly — things like suspension damper rates or high-frequency wheel dynamics, which are exactly the kind of signals that get missed or aliased on loggers that pre-filter or downsample the bus.
From Raw Bus to Answers: VBOX Test Suite
Capturing everything is only useful if you can make sense of it afterwards. This is where VBOX Test Suite, Racelogic’s analysis software, comes in:
Post-test channel selection
pick any combination of logged CAN signals after the fact, without having planned for them in advance
Unlimited re-analysis
the same raw log can be revisited any number of times for different questions, different projects, or different engineers
Pre-configured test plugins
standard test types (braking, ADAS scenarios, lane manoeuvres, etc.) come with built-in pass/fail logic, so results are available almost immediately rather than requiring a custom analysis script
Open file format
because the data is stored as standard .asc, it’s also compatible with third-party CAN analysis tools if your workflow needs them
In practice, this means the test engineer in the car doesn’t need to be the same person who defines what’s analysed later — the data supports both.
Where Full CAN Logging Is Used
Full-bus CAN/CAN FD capture on VBOX 4 shows up across almost every serious vehicle-testing discipline:
ADAS and autonomous vehicle testing
correlating radar/camera CAN outputs, target vehicle data, and GNSS position for pass/fail scenario validation
Vehicle dynamics testing
synchronising suspension, steering, and chassis CAN signals with precise position and speed
Brake testing
combining CAN-sourced brake pressure/ECU data with VBOX 4’s high-accuracy brake-stop detection
Powertrain and hybrid/EV validation
capturing high-bandwidth CAN FD traffic from battery management and motor control units
Motorsport and performance testing
logging full vehicle telemetry without needing to predefine every channel before a session
Accident reconstruction and durability testing
where every available signal may become relevant during post-incident analysis
VBOX 4 vs. VBOX 4 ADAS: Which CAN Setup Do You Need?
| VBOX 4 | VBOX 4 ADAS | |
| CAN ports | 4 isolated ports (RL CAN, CAN, CAN FD 1, CAN FD 2) | Adds a dedicated additional CAN FD port and a fourth bus for Racelogic module input |
| Full CAN/CAN FD bus logging | Yes | Yes |
| Dual CAN bus sync | Yes (2 buses to one .asc) | Yes, with extra bus headroom for complex ADAS rigs |
| GNSS logging rate | Standard high-rate GNSS | Euro NCAP-compliant 100 Hz logging |
| Positioning accuracy | High-accuracy GNSS | Centimetre-level with RTK Base Station or NTRIP |
| Best suited for | General vehicle dynamics, performance, and durability testing | ADAS/AV scenario testing with multiple moving/static targets, driving robot integration |
If your test plan involves radar/camera fusion, driving robots, or Euro NCAP protocol compliance, VBOX 4 ADAS is the version built for it. For general performance, dynamics, and CAN-heavy powertrain work, the standard VBOX 4 already covers full dual-bus logging.
How to Set Up Full CAN Logging on VBOX 4
- Connect your CAN sources.
Wire the vehicle/sensor CAN bus into CAN FD 1 (and CAN FD 2 if logging a second bus). Connect any Racelogic modules or displays via RL CAN.
- Open VBOX Setup.
The software will detect connected Racelogic modules automatically and populate available channels.
- Enable full bus logging on the CAN FD port(s).
Set the baud rate to match the vehicle bus, or use auto-detection where supported. No channel pre-selection is required — the entire bus will be captured.
- Configure CAN Pass Through (optional).
If you need to output specific signals to a third-party system in real time, map up to 8 messages / 16 signals from RL CAN out through the CAN port.
- Run the test.
VBOX 4 logs the full raw bus, GNSS-timestamped, into a single .asc file — even across two independent buses simultaneously.
- Analyse in VBOX Test Suite.
Pull in any channel combination after the fact, apply pre-built test plugins for instant pass/fail results, or export to a third-party CAN tool.
Frequently Asked Questions
Does VBOX 4 support CAN FD, or only classic CAN?
Both. The CAN FD 1 and CAN FD 2 ports accept either raw CAN FD or classic CAN 2.0 traffic, so VBOX 4 works on legacy and modern high-bandwidth vehicle networks alike.
Can VBOX 4 log two CAN buses at the same time?
Yes. Its two independent CAN FD ports can each capture a separate vehicle bus, and VBOX 4 synchronises both into a single time-aligned .asc file — no manual merging required.
Do I need to select which CAN channels to log before a test?
No. VBOX 4’s full-bus logging captures every frame on the connected bus automatically. Channel selection happens afterwards, in VBOX Test Suite, so you’re never locked into a pre-test decision.
What file format does VBOX 4 use for CAN logs?
Logged CAN and CAN FD data is written to a standard .asc file, which is compatible with VBOX Test Suite as well as most third-party CAN analysis tools.
How is CAN data time-synchronised with GPS/GNSS data?
Every CAN and CAN FD frame is timestamped against VBOX 4’s GNSS clock at capture time, so position, speed, and bus data can be correlated to the same moment with high precision — critical for tests like ADAS scenario validation or brake-stop analysis.
How many Racelogic module channels can I connect?
Up to 32 Racelogic module channels can be logged via the RL CAN port, with automatic recognition of connected modules such as TC8 and FIM03.
What’s the difference between VBOX 4 and VBOX 4 ADAS for CAN logging?
Both support full dual-bus CAN/CAN FD logging. VBOX 4 ADAS adds an extra dedicated CAN FD port and bus headroom for driving-robot and multi-target ADAS rigs, plus 100 Hz Euro NCAP-compliant GNSS logging.