How to send information via J1939?

[iva]

Thanks a lot! I'll try to work it out.

[iva]

As i understand, we have only int32-type for tags on transmission.
Is it possible to form 8-bytes message at once. In other words: how to prevent sending a message which is not finished?

[mark.monroe]

You need to update the tag value with the complete value you want to send. There is no way to partially update a tag's value, then send out the data when you are done.

In the FreeCAN Excel spreadsheet I always thought that you could limit the data you wanted to send to a single bit up 4 bytes, and any combination in between. Obviously only values that can be contained in the CAN memory register that you have specified would work.

[fabiop]

Hi
with CAN bus sometimes it is really necessary to control *when* a telegram is sent. For example, a telegram contains four tags (A, B, C, D), and the value of those tags shall be aligned.
Let's say initially A=0, B=0, C=0, D=0.
I want to send a telegram with A=1, B=2, C=3, D=4.
So I write a script:

A = 1;
B = 2;
C = 3;
D = 4;

The problem is: as soon as the first instruction is executed, the CiX module sends a telegram with A=1, B=0, C=0, D=0, which is wrong. Is it possible to send a single telegram at a given time? As the original writer of this post alredy mentioned, document "First steps with CiX-CAN FreeCAN.pdf" at page 35 explains something about HRA, HRB but the information is not complete.

Please explain how to use HRA, HRB to send a telegram by direct command