LAUNCHXL-F28P65X: How to control SCI TRANSMIT FIFO Interrupt for when data is ready

Hi Ashwin,

Ashwin Bhaskar said:

From my understanding the transmit FIFO generates interrupt when the data in the FIFO falls below the preconfigured threshold.

If this is true every time the threshold falls below the FIFO level even by one , it generates interrupts regardless of if you have data to transmit or not.

Your understanding is correct.

Ashwin Bhaskar said:

How can i only generate interrupt in FIFO if and when i call the API for writing data into my FIFO

To do this, you can just call the TX FIFO write function (SCI_writeCharArray()) to write to the TX FIFO in your main code whenever you have data ready to send; there should be no TX interrupt needed. This function will wait in a polling loop until there is enough space in the FIFO to write all of your data. 

If you're worried about a performance hit due to polling loops in your main code, you could take the approach of enabling the SCI TX interrupt in your main code whenever you're ready to transmit data and then disabling it in your ISR. Then the interrupt will happen (most likely immediately) whenever you enable it, and the FIFO has enough space. If you're transmitting infrequently and with less than 16 characters at a time though, you shouldn't see any performance issues, in which case I would recommend just calling SCI_writeCharArray() when you're ready to transmit.

Best Regards,

Delaney