Lag on Display

Connectivity General Discussion
1

Hi All,

ok loving the product works well, Im conencting via “generic” EML adapter on the ODB port, which the tablet connects to via wireless, all works BUT there is an “annoying” lag on the display is there anything obvious I need to look at ?

thanks !

2

You may wan’t to try these settings:

RealDash has two settings that may increase the data rate on some vehicles. You can access these settings by going to Garage and connection settings:

Use Multipid Request
This setting works if you have relatively new vehicle with CAN bus. When this option is enabled, RealDash constructs a multipid request command and when supported by vehicle can receive multiple values in one reply. This will increase the data rate considerably. On older vehicles this setting may slow down the time to connect to vehicle and therefore its disabled by default.

Request Only First Reply
On newer vehicles some requested information may be contained in several modules. For example engine RPM may be stored in ECU and TCU of the vehicle. Enabling this option will instruct the adapter to respond with first available value and not wait until all modules have responded to the request. This may increase the data rate in some cases.

3

Excellent, I shall go out and try ! will report back : ) :slight_smile:

are any specific mediums faster, i.e wifi, bluetooth, hard wire, or is there little in it ?

thanks !

4

The bottleneck on data rate is always the vehicle. I’ve seen over 200 values per second from OBD2 over standard Bluetooth so that is not an issue.

You can see the actual data rate by:

  • Edit the dashboard and add Text Gauge
  • Link Text gauge to ‘Calculated Values->Data update rate (values/s)’
  • Exit edit mode and observe how many values you get per second.
5

I use a mixed protocol, some of the values ​​are taken from the OBDII gateway, and of course the lion’s share is interrogated by RAW -CAN. But this does not stop me from getting values ​​with the speed of lightning. My speed is more than 600 values ​​per second. Of course, I understand that using instant values, such as RPM, SPEED, TPS via OBD II protocol, this will not give that visual effect on the display. And so I get OBD II values ​​of secondary sensors and more static values.
IMG_20200304_161631.jpg

6

In my case 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?

7

The protocol itself is built on the principle of dialogue, and these are significant delays, which, by the way, still need to be checked for errors, so the more such requests are in the current session, even the car’s ecu itself will give answers with a delay, because in addition to communicating with OBD, you need to control several actuators and interrogate a dozen sensors.
And it’s all sequential…
From experience, I can say that sensors, for example, temperatures, can be polled once every 5 seconds, it is desirable to poll the speed signal constantly …