Blackfin UART Interrupt/Callback for receiving data

Question

Hi,
I am having trouble structuring a simple program to receive data from the Blackfin UART1.  Data is received over the UART1 every second, so I'm planning on creating an interrupt service routine to read in the data and store it to a global string array .  After reading the following page on Blackfin callbacks,
http://zone.ni.com/devzone/cda/tut/p/id/3244
I believe this is the general way I should approach the problem:
Main VI:
- Static VI reference that references the UART interrupt service routine VI
- Static VI reference connects to BF UART Open block, BF UART Control block, then to the UART interrupt service routine
- Global string array indicator
UART interrupt service routine VI:
- UART Read block with the output buffer appending string to a global string array
This is not working--the global string array does not update.  I have been able to read the data through the UART1 in another VI, but this was not triggered by an interrupt.  Is this the right approach to the problem or does someone have a sample VI that I can look at?
Thanks in advance,
Chris

Answer 1

Hi Chris,
I would not recommend using the BF UART VIs in an Interrupt VI -- VDK is very strict about what is allowed in ISRs, and in general, it is best to do as liitle as possible in ISRs. Also, the callback will execute when the buffer is full (not necessarily once a second).
Instead, you could do a simple timed loop application that has a period of 1s, and do the UART Read in the timed loop. Or, you could even do something as simple as put the BF UART Read in a while loop that contains a Wait Until Next ms Multiple function to cause the loop to execute once per second. I recommend using the UART echo example as a starting point (attached).
Michael P
National Instruments
Attachments:
UART echo.vi ‏39 KB