ELM327 wireless OBD2 adapters are popular tools for accessing vehicle data. Many car owners want to know if they are compatible with the Carly app. This article delves into the specifics of using an ELM327 with Carly, focusing on the ATST (Adapter Timeout) command and its impact on performance. Understanding this setting is crucial for optimizing data retrieval speed and ensuring a smooth diagnostic experience.
Understanding the ATST Command
The ATST (Set Timeout) command controls how long the ELM327 adapter waits for a response from the vehicle’s ECU (Engine Control Unit) after sending a request. This timeout, defined in increments of 4 milliseconds, prevents the adapter from endlessly waiting for data if there’s no response. The default setting is typically 32 (approximately 200 milliseconds).
When you request a specific data point (PID – Parameter ID), often multiple ECUs might respond. The adapter needs to know how long to wait before concluding there’s no more data and moving on to the next request. This is where ATST comes into play.
Carly’s Adaptive Timing and Optimization
Carly offers two primary modes for managing the ATST setting: “Adaptive Timing” and “Optimized Timing.”
Adaptive Timing (Enabled)
With Adaptive Timing enabled, Carly relies on the ELM327’s internal logic to determine the optimal timeout. This essentially reverts to the default ATST value and allows the adapter to handle the timing based on its own algorithms. You can force this behavior by setting Expert Settings ‣ OBD Tweaks / Adaptive Timing to "Enabled" in the Carly app. This will restore ATST to the default and generally works well in most situations.
Optimized Timing
When “Optimized Timing” is selected in Carly ( Expert Settings ‣ OBD Tweaks / Adaptive Timing to "Optimized"), the app takes control of the ATST setting. It initially sets a maximum timeout (ATSTFF) to gather responses from all potential ECUs. Subsequent requests are then optimized based on the number of responses received in the initial query. If, for example, only one ECU responded to the RPM request, Carly will instruct the adapter to retrieve the RPM data and return immediately after receiving one response, effectively bypassing the timeout. This can significantly improve data refresh rates.
However, “Optimized Timing” may not be compatible with all vehicle communication protocols, particularly older ones like ISO 14230, which are inherently slower. In such cases, “Adaptive Timing” might be more reliable. Older systems may struggle with the aggressive timing strategy employed by Carly’s optimization.
Finding the Best Setting for Your Vehicle
To determine the optimal setting for your vehicle and ELM327, experiment with both “Adaptive” and “Optimized” timing modes in Carly. Monitor the data update rates in each mode and choose the one that provides the fastest and most stable connection. You can also adjust the “Reply Timeout” setting in Carly, though higher values generally favor the “Optimized” approach.
Keep in mind that even with optimal settings, certain vehicle communication protocols, like ISO 14230, have inherent limitations in speed, typically capped at around 2-3 Hz (or 10-15 PIDs per second).
Conclusion
Using an ELM327 wireless OBD2 adapter with Carly is possible, and understanding the ATST command and Carly’s timing optimization features can greatly enhance performance. While Carly’s “Optimized Timing” often yields faster data rates, compatibility varies depending on the vehicle’s communication protocol. Experimentation is key to finding the best setting for your specific car and adapter. Remember that older car models might be limited in their data transfer speed regardless of the settings.
