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I reached out a while back about the custom VPW payload support and had my first track weekend last weekend. It worked great! I now have brake module data that I never had before which is awesome.
I have a question about how the software handles VPW packets with different headers.
Since the GM VPW bus is very slow (10.4 kbps), GM has DPID support. Which basically allows you to cut down on the number of requests needed. You can request up to 4 PIDs with a single request message. This has the advantage of getting rid of up to 3 messages transmitted on the bus.
Does the software do a request, and then wait for a reply before moving onto the next request/PID?
Reason I ask is that I am able to achieve higher throughput with some diagnostic tools I programmed (for development of hardware) by taking advantage of DPIDs.
The general process is to send a request message to a module, asking for up to 4 parameters. The module replies with 4 seperate messages like normal, of the PIDs in question as quickly as it can, and time synched. As the messages come in, i know the response prefix since I know I sent the DPID request. So i don't necessarily have to do a single request/response when polling, which helps my throughput.
I'm not sure if this is something that's possible to support, as it would require multiple responses to a single request to be processed for different PIDs. Almost like a filter as they come in.
You can see on the green and yellow traces (brake and throttle), the refresh rate can be a bit slower, which i know is due to the fact that they come from different modules, and probably waits for one to respond before requesting a pid from the other. I poll multiple parameters from the ECU so using DPID could help.