I am working on implementing the Storm SoC on my DE0-Nano. Everything is going smoothly, but I am having trouble with the Uart TX Interrupts.

I know that this interrupt is called whenever the Uart is not transmitting, so I am trying to set it up to read from a buffer in software and turn itself off when the buffer is empty. I have tried to disable the interrupt within the ISR as well as set a flag which then turns off the interrupt when it reaches the if statement in the main loop.

The program seems to come to a halt either way when I try to disable the interrupt. To disable the interrupt I have tried the 3 following statements (and I think all possible combinations of the 3)

VICVectCntl2 = 0; // enable and channel select = 2
VICIntEnable ^= ( 1 "leftshift" 2 ); // enable channel 2
VICIntEnClear = 2;

Please ignore the leftshift part, it won't let me put the correct C syntax for left shift there without screwing everything up.


Please let me know what I am doing wrong. Thanks!

Chris

Thanks to the help of Stephan I have solved the problem.

There are two possible solutions. To disable the TX interrupt you would have to do VICIntEnClear = (1 "shift left by" 2) not VICIntEnClear = 2 as I was mistakenly doing earlier.

The option I'm going with hover is to change the trigger mode from going off constantly if the interrupt is high (which is will almost always be if the UART isn't constantly being filled) to only changing on edges. To do this you just need to add in VICTrigMode |= (1 "shift left by" 2);