FreeRTOS output: <NEORV32-IRQ> Unexpected IRQ! cause=0x8000000b </NEORV32-IRQ>

[victorlga]

Hi!

I am new to neorv32, risc-v, FPGA, and open source, sorry if missed any guidelines or made any dumb questions.

I am trying to run FreeRTOS with NEORV32 in my FPGA DE0-Nano.

My output is:

[19:17:59:737] ␍␊
[19:17:59:737] <NEORV32-IRQ> Unexpected IRQ! cause=0x8000000b </NEORV32-IRQ>␍␊
[19:17:59:785] ␍␊
[19:17:59:785] <NEORV32-IRQ> Unexpected IRQ! cause=0x8000000b </NEORV32-IRQ>␍␊
[19:17:59:817] ␍␊
[19:17:59:817] <NEORV32-IRQ> Unexpected IRQ! cause=0x8000000b </NEORV32-IRQ>␍␊
[19:17:59:848] GPTMR IRQ Tick␍␊
[19:17:59:865] ␍␊
[19:17:59:865] <NEORV32-IRQ> Unexpected IRQ! cause=0x8000000b </NEORV32-IRQ>␍␊

It was supposed to be only [19:17:59:848] GPTMR IRQ Tick. ChatGPT said:

The FreeRTOS demo you are running seems to handle General Purpose Timer (GPTMR) interrupts, but there might be other interrupts enabled or pending that aren't being handled, such as the machine external interrupt (MEI).

But I have no idea where this MEI is coming from. Is this a common issue or am I configuring badly my top level?

Also, I will share here the project when it's done. I am building a reaction wheel FOC controller for nanosat applications using NEORV32. It is my capstone project for an undergraduate Computer Engineering course at Insper (Brazil) in partnership with Brazil's Ministry of Science and Technology.

[AndreCorreaSantos]

I was wondering the same thing!

[NikLeberg]

Hi @victorlga!

I am new to neorv32

Hello and welcome to neorv32. You didn't break any rules no worries. :)

Is this a common issue or am I configuring badly my top level?

It's not an issue I've heard before. How did you configure your toplevel? Could you copy your VHDL into here so we can have a look?
I'm assuming, that for the C-code, you just used the FreeRTOSS example from stnolting/neorv32-freertos, right?

I am building a reaction wheel FOC controller for nanosat applications using NEORV32.

That sounds AMAZING! Feel free to show & tell your results here.

[NikLeberg]

The corresponding toplevel input to neorv32 that is capable of triggering this interrupt is mext_irq_i which is typically just statically connected to 'L' i.e. a logic low level. Did you connect something to that input?

[victorlga]

Thanks! @NikLeberg this was the source of my issue

[stnolting]

Hey @victorlga.

As @NikLeberg has already mentioned cause=0x8000000b indicated a interrupt request from the top's mext_irq_i ("machine external interrupt"). By default, this interrupt source is disabled via the mie CSR; so the interrupt cannot trigger until the according enable-bit is set. So I assume you've customized the default FreeRTOS example?