CAN Output Messages data rate

[Turby]

I have a query regarding the CAN output message data rate. I have enabled all of the PDM CAN output messages and with an attached CAN bus logger I notice that I am receiving CAN output messages 0x500 to 0x505 every 10 milliseconds rather than the expected 50 milliseconds.

This is a frequency of 100Hz rather than the expected 20Hz. Has the output rate changed to that shown in the user manual and is it configurable ?

Whilst having a higher frequency is an advantage, its also using 5 times the expected can bus bandwidth...

I'm using a PDM 30 with the firmware version 1.80A.

[adrian]

The 0x500 to 0x505 messages from the PDM are compound messages, so they have an additional identifier within the data so that a much larger number of channels can be sent on the same address. This way it only takes up 6 addresses rather than 30 to send all the PDM default channels.

So when you have a message with 5 compound ID's to get a transmit rate of 20Hz for a particular channel you actually have to send the message 5 times faster, so in this case 100Hz.

In the below image you can see the raw CAN messaging. If you look at the time stamps you can see the actual time between two messages with the same compound ID is 50ms.

PDM Compound ID.png (20.86 KiB) Viewed 9988 times

[Turby]

Thanks Adrian, you quite correct, it seems I missed that nugget of info and was just looking at the can id