J1939 interpreting Data

[Sergio Ramos]

Hello!

If anyone has any experience or any examples of using the SAEJ1939 Protocol, I would really appreciate some help. I am using a NOx sensor and would like to extract its data to an HMI. 

I am currently trying to figure out how to utilize the parameters of the J1939 Protocol. I have the values of the Protocol from the user manual but I do not know how to interpret it for the Visilogic Function blocks. For example, to extract the NOx value would I say there are 2 bytes of max data allowed? (Since there a low and high bytes). And for data pointers, does it "point" to the address of a byte or a bit? Also, once the data is received, where would it be stored? And how can I convert it to a readable value? Would I have to convert it from a BIT to a NUM eight times (Since I get a bit of information and not a byte)?

I would really appreciate any thought or comments.  I have attached the manual, some screenshots, and my program so far. 

Thanks again. 

trial j1939.vlp

 

Conti UniNOx12V_spec_11 03 08 (1).pdf

[kratmel]

I try to check your code... I recommend to start new project with basic J1939 function.

I think you find this sample code and understand idea how to convert MI vector to separate MI and MB.

[Sergio Ramos]

Hello, so for that code, it would make an array of all the bits of the J1939 Protocol. Would it be correct to assume that I could convert that array into a a readable number by the function BIT to NUM? And also, I think I figured something out, from what you said. The bit array will start say, on MB 1000, as the example, therefore the first 8 bits would be on MB 1000-10007. So if I needed the first 8 bits only, would it look something like this?  

The formula at the end is to convert the NOx value into ppm (parts per million). 

 

I once again thank you for your help!

J1939 TRIAL V2.vlp

[kratmel]

20 hours ago, Sergio Ramos said:

The bit array will start say, on MB 1000, as the example, therefore the first 8 bits would be on MB 1000-10007. So if I needed the first 8 bits only, would it look something like this? 

Yes, Visilogic have all needed FB for convertion. One thing that you must do - find the way to test - is it reading from sensor correct.