[En-Nut-Discussion] Lost caracter with At91 UART0

Ulrich Prinz ulrich.prinz at googlemail.com
Sun Dec 18 02:12:41 CET 2011

Hi Remi,

Am 17.12.2011 02:01, schrieb Remi Bilodeau:
>  I found my problem...
> Nut/OS seem to not use nested interrupt... 
This is not the job of the OS itself. But we might miss some setup
functions that enable easy user control of the interrupt controller.

We set priorities but make not full use of the controllers options.
Nut/OS grew up from AVR which does not support any kind of priorities.

ARM hen introduced priorities but it was up to the chips manufacturer of
how to do that.

With Cortex it is unified by ARM LTD. for all Cortex designs and it is
availbale through CMSIS interface. With completing the merge to Nut/OS
we will provide the needed functions to control the NVIC of Cortex.

If you find a way to easy setup the AT91 interrupt controller for
priority handling, please provide the information here or post a patch.

Afai a simple setup of the interrupt controller is done providing some
levels of priority.

Ah, please check the usarts setup file at91_usartX.c. In that you should
find a #define right at the beginning. This sets the interrupt priority.
I did not check, if the complete code structure is provided to control
the priotity from user code via ioctl().

> Any idea about this and nested IRQ ??
I am not sure if nested interrupts are supported by AT91. As I said it
was to the chip manufacturer to implement interrupts with the older ARM

Best regards

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