CAN output, confirm blank field = no message

Discussion and support for MoTeC Power Distribution Modules

CAN output, confirm blank field = no message

Postby phatbob on Wed Jun 27, 2012 6:14 am

Hi

we have checkboxes to 'select' weather status data is transmitted, that is great

for the actual optional CAN outputs, we dont have checkboxes but it actually seems to send, if something is defined, and not send, if something isn't.

if one defines the four additional, optional messages with an address, it appears that only data is transmitted for each byte that actually has a channel defined for it. In other words, if you have nothing in the box, there is no message transmitted at all. So if you have say a base address of 123 defined and you have a channel in the 1st and 3rd byte, that nothing will get transmitted on the second byte. Can someone confirm that this is indeed correct ? I am using this to have two devices communicate to a single device (one of the senders is the PDM and I didn't want it to conflict with the other sender).

Can we also confirm that if we have one of the messages defined with a base address, but dont populate any of the 8 fields, that no such message will be sent ?

THanks
phatbob
 
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Re: CAN output, confirm blank field = no message

Postby JamieA on Fri Jun 29, 2012 10:34 am

That is a reasonable question, but I dont really know for sure.

Ill see what I can find out.

-Jamie
JamieA
 
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Location: Melbourne, Australia

Re: CAN output, confirm blank field = no message

Postby YuriK on Fri Jun 29, 2012 5:57 pm

Hi,
If you don't check any of the Standard messages nothing is sent on that address. Same is true for custom messages. In other words if you see "Disabled" in Settings - nothing is being sent. If you see "Address=xxx" - the packet is sent to xxx address.
As far as I understand when the message is sent it sends all 8 bytes so if you selected 8 channels with value 1 in every one of them, your message will look like 01 01 01 01 01 01 01 01. If the value of the first channel is changed to 0 then the message will look like 00 01 01 01 01 01 01 01. If you go and delete the first channel from the message setup, then the output will still be 00 01 01 01 01 01 01 01.
In general you shouldn't worry about conflicting messages as long as they don't have the same address. Sending multiple messages with the same address will cause collisions
YuriK
 
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