Hi firstly, in order to make code more readable and importable it is important to post it between two sets of three backticks - ``` - see this post for more details - How to share code or flow json
You should go back and edit your post.
Secondly, setting msg.payload=00000008 is just setting the number 8 - e.g. you might as well have written msg.payload=8 - in other words, this in not correct.
It is more likely you need to send a Buffer
An example would be - to send 000000000000008c02010000013feb55ff74000f0ea850209a6900009400d6120000 you need to convert it to a bytes (a Buffer) which can be either hard coded or converted in a function node like this...
msg.payload = Buffer.from("000000000000008c02010000013feb55ff74000f0ea850209a6900009400d6120000","hex");
return msg;
Here is some proof...
Lastly, there is also a CRC to calculate to append to the end. This is not so straight forward.
In this post here an example where I calculated CRC in a function node for another user - you might be able to adapt it.
