Transmit Specific Message, how?

D153, D175, C125, C127, C185 and C187 forum

Transmit Specific Message, how?

Postby Robbied on Sun Jun 27, 2021 10:13 pm

I need to transmit a specific message from my C127, in order for a 3rd party piece of hardware to send its CAN data. (which is setup via a supplied .DBC file)

This message needs to be "0's on base address 300 (on CAN 1, in this case)

How do I set this up to do this? And the base address for the data it will be recieving is also 300. In my mind this is a conflict, but I might be interpreting this incorrectly. Any help appreciated!

Many thanks
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Re: Transmit Specific Message, how?

Postby adrian on Mon Jun 28, 2021 8:30 am

Dash Manager doesn't let you send and receive on the same address, the only way to set this up would be to have the transmit on one CAN bus and the receive on the other and physically wire them together.

What is the device you are trying to control? It is pretty rare to have transmit and receive on the same address.
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Re: Transmit Specific Message, how?

Postby Robbied on Tue Jun 29, 2021 1:42 am

Hi,

Thanks for the response, the device is a Liteblox battery. I have had it connected to the C127 on the bench, working great with the imported DBC file and set up as the only device on this bus. I could see all the values and display them as needed on the dash.

Now that the car is built and everything transferred to the actual car harness, i have no CAN data.

The battery has been back to the manufacturer for a firmware update in the meantime, but they assured me nothing has changed in the CAN settings. However they have said unit needs to receive '0's' on 0X300 for it to start transmitting. (its base transmit address is also 0X300..)

I didnt have to do anything like this when I had comms on the bench, hence Im now scratching my head a little...

Edit; I belled out the wiring again for my own piece of mind today. All ok and with 60 ohms across the bus, (device to device with 120ohm each end).
Robbied
 
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Re: Transmit Specific Message, how?

Postby adrian on Tue Jun 29, 2021 8:56 am

That is a bit of a strange setup, you really shouldn't have 2 devices transmitting the same address on a CAN bus. If they can't change that behaviour then the only way will be to wire the two C127 CAN buses together.
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Re: Transmit Specific Message, how?

Postby Anthony on Fri Jul 02, 2021 12:21 am

Robbied wrote:Hi,

Thanks for the response, the device is a Liteblox battery. I have had it connected to the C127 on the bench, working great with the imported DBC file and set up as the only device on this bus. I could see all the values and display them as needed on the dash.

Now that the car is built and everything transferred to the actual car harness, i have no CAN data.

The battery has been back to the manufacturer for a firmware update in the meantime, but they assured me nothing has changed in the CAN settings. However they have said unit needs to receive '0's' on 0X300 for it to start transmitting. (its base transmit address is also 0X300..)

I didnt have to do anything like this when I had comms on the bench, hence Im now scratching my head a little...

Edit; I belled out the wiring again for my own piece of mind today. All ok and with 60 ohms across the bus, (device to device with 120ohm each end).



Just had a quick look at the manual.
300 is Transmit
301 & 302 are Receive

You can generate a constant channel value in dash manger under calculations > constants.
You will then need to add that channel into the transmitted channels in the comms menu
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Re: Transmit Specific Message, how?

Postby Robbied on Fri Jul 02, 2021 4:23 pm

I interpreted it this way too, although I think messages are also coming from the battery on ID 300, according to both the manual and their .DBC file the following;

BITS SIZE GAIN RANGE DESCRIPTION
[0] 1 1 [0-1] Charge override
[1] 1 1 [0-1] BT On
[2] 1 1 [0-1] BT Off
[3] 1 1 [0-1] Disable Crash
[4] 1 1 [0-1] Reset Killswitch

I have asked them what to do next, as im certain that when I had comms working on the bench previosuly I didnt have to set up any transmit messages from the C127. Im pretty sure of this, mainly as I dont know how to do it(!)

All a bit frustratiing as this is the last piece of the puzzle on the electrical system and it would be nice to get it working...
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Re: Transmit Specific Message, how?

Postby adrian on Mon Jul 05, 2021 12:20 pm

Is it possible to splice in the other CAN bus so you can at least test sending the 0x300 message to see if it works?

To transmit a message, create a new CAN template, select 'Transmit Message' from the drop down and set the address to 0x300. Id probably set the transmit rate to 1Hz for the test. You don't need to set any channels, it will send all zeros.
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Re: Transmit Specific Message, how?

Postby Robbied on Tue Jul 06, 2021 5:45 am

Thank you for your help on this, I managed to solve it finally(!)

The DBC file had somehow become altered/corrupted so that message ID 300 was set to 'recieve message' rather than 'transmit message'. Once I swapped it, it all came alive again and I finally have my BMS data on the dash :)
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