AVR-Chat

Hi all,

 

I have an Arduino Mega2560 board and programming it with Studio 6.1 and AVR
GCC. I am debugging with a JTAG ICE3

 

The issue is that there is no transmit register empty interrupts for USARTS
1 to 3. USART0 is ok.

 

This code is used to set the control register for USART1 but nothing happens
and there is no interrupt firing.

 

 

    UART1_CONTROL |= (1 << UART1_UDRIE);

 

 

I am using code that is at the link below and if I use UART0 it all works
and interrupts are working.

 

I just don't get any interrupts with USART's 1 to 3.

 

I do have USART1 enabled in the header file.

 

Reading back both the STATUS and CONTROL registers, the bit for URDIE is set
in both so the interrupt should be firing.

 

 

I do have sei() in the code after the UART is initialised. As I said, UART0
works.

 

I have used a #error at points in the code to confirm what's been compiled
and it is all as expected.

 

This is a link to the library.

 

https://github.com/andygock/avr-uart/wiki

 

Appreciate any pointers to consider?

 



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As a follow up.

 

I checked the disassembly and the vector at $004A is correct and points to
the interrupt handler.

 

It's almost as if the interrupt is masked but when I debug into the code
that sets the CONTROL register, I can see that UDRIE is being set so the
interrupt should fire as it is level triggered.

 

Very puzzling.

 

Dave.



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