Yes i found out that that was a bit tricky because i use the serial receive to receive 3 bytes the first is a specific number 254 the second is data byte 1 and the third is databyte 2. The first byte is to have some kind of synchronisation (in my case the second and third byte never have a value of 254)...
To create some kind of buffer for the serial receive i made use of the FIFO registers in labview FPGA.
A small explanation of how the piece of code works.
As you can see there are 2 whileloops now the lower whileloop is the same as i explained earlier (or simular because it could be that i made some small space saving changes...) but at the end you see that i use the FIFO write function
To create a FIFO: go to the project explorer right-click on the FPGA target select new => FIFO
A propperty dialog will appear where you can set the settings. I suggest you you click the help button for more info(if you use less then 20 received bytes at one time set it to flipflop it will save some memory on the FPGA).
When you select ok then you will see that there is a FIFO created in the fpga subtree. To place it on the block diagram just drag it from the project explorer to the block diagram.
If you right click the item on the block diagram you can select 3 methods "read", "write", and "clear" in the receive we want to write the data to the fifo.
( as you can see i used a "convert from boolean array to number" because the fifo doesn't work with boolean arrays.)
i set the timeout value to -1 this means that it wil wait forever before it times out.
now for the upper while loop the functionality is as followed: again you see that the timeout is set to -1 so the whileloop will not loop any further because the FIFO read will never timeout so it waits untill there is something in the FIFO.
If there is something in the FIFO and for example it is not equal to 254 then the case is false (where in my case nothing happens) so the case will end and the whileloop is run again untill the FIFO read is equal to my startbyte 254 if that is the case then the second while loop will be active and i extract the 2 data bytes by using a case structure that is connected with the loop iteration.
So the first time it is run the iteration will be "0" so i extract the first databyte by using the HDL node ( i use it because labview doesn't know how to convert from numer to bitlevel or from boolean array to bitlevel besides using a for loop and the index array function and in VHDL this programmed very easily). You can also use a flat sequence to do the same (but i use my program to show the different ways to programming)
The false constant is to make sure the loop keeps running.
when te loop is run for the second time i extract the second byte and when the while loop runs for the third time i make the false constant to true so te whileloop will exit and run again in the upper whileloop waiting for the next set of bytes to be received
in attachement you will find the solution of the serial receive with the fifo registers.. this works fine for my program.
If you still have any question i wil do my best to answer them as quickly as possible
kind regards
Snakebomber
