I noticed there is the delay caused by smartphone (or maybe Realdash). I watched bluetooth signals by analyzer and saw that after ELM327 sent answer, it takes more than 50-75 ms before Realdash send new pid request. What is the reason for this? Is this lag depends on Realdash or specific smartphone?
Hard to say as delays are very much hardware, adapter, vehicle specific. OBD2 connection will never be ‘fast’ due its polling nature.
No, in my case i’m make sure that my realdash doesn’t send new PID request right after it recevied prvious answer. Vehicle and adapter doesn’t matter. Realash waits 50-75 ms before send new PID request. Why is realdash behaving like this? Maybe I can somehow fix it in options or maybe you can fix it in new release?
Latencies vary between setups. That 50-75ms may be the case on yours, on some other setup it could be 10ms and on others 100ms.
As I said, OBD2 connection will never be fast. If I work a hundred hours to shave off 50ms, it will still have more than 100ms of delay between values due the request-receive nature of the protocol.
If you are using custom XML, you may want to check if you have complicated ‘conversion’ attributes in there. They can parse somewhat slow.
Ok, I’m designing my bluetooth adapter so i can chose any protocol. What protocol would be better in terms of latency and where I can find description file for it?
There is no definitive answer. Every vehicle has their own quirks, they may return some values fast, others slow. Many vehicles also vary the delays during runtime depending how ‘busy’ the ECU is and so on, as diagnostic port messages are typically of low priority to ECUs.
I mean - is there bluetooth protocol that supported by Realdash that doesn’t base on “polling”? Is there the way to set constant bluetooth stream to realdash without need to send pid request?
With factory ECUs, most performant way to connect is CAN adapter. See supported adapters here:
http://realdash.net/manuals/supported_can_lin_analyzers.php
If your vehicle is older and has no CAN, then only option for fast data rate is installing aftermarket ECU.
Ok, thank you! I’ll try CAN then