System reboot without NRST low

Peter Rabold · ‎2018-02-27

Posted on February 27, 2018 at 11:02

I'm using an STM32L152 with IAR embedded workbench.

This MCU has an external reset pin (NRST) which is bidirectional. The MCU outputs a low signal if its reset system detects a watchdog reset, software reset or low-power management reset. With other words: If I reboot the system using HAL_NVIC_SystemReset() the NRST pin is taken low.

Question: How can I reboot the system by software without signalling it at the NRST pin? Can I inhibit the NRST output pin or is there a way to call the reset vector to reboot?

Thanks for your support.

#reset #nrst-pin

Andrew Neil · ‎2018-02-27

Posted on February 27, 2018 at 12:03

Isn't that what

HAL_NVIC_SystemReset()

does ?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Andrew Neil · ‎2018-02-27

Posted on February 27, 2018 at 12:04

Yes, you can call the reset vector - IIRC, the IAP app notes do that.

But this will not give you a full hardware reset

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Andrew Neil · ‎2018-02-27

Posted on February 27, 2018 at 12:06

How can I reboot the system by software without signalling it at the NRST pin?

Why do you want to do that?

If you explain what you're trying to achieve, people may be able to suggest ways to reach that goal ...

http://www.catb.org/~esr/faqs/smart-questions.html#goal

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Peter Rabold · ‎2018-02-27

Posted on February 27, 2018 at 12:13

Because I have another MCU on that NRST reset line (on Arduino shield) which must not be reset.

Peter Rabold · ‎2018-02-27

Posted on February 27, 2018 at 12:15

What is the IAP app ?

Can I just make a call to the reset vecor at address 0 or how should that work ?

And what is not reset in that case ?

Andrew Neil · ‎2018-02-27

Posted on February 27, 2018 at 13:05

See the Product Page -

http://www.st.com/en/microcontrollers/stm32l152vb.html

- it has a full list of App Notes and other support materials

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Andrew Neil · ‎2018-02-27

Posted on February 27, 2018 at 13:05

So don't do that, then?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

henry.dick · ‎2018-02-27

Posted on February 27, 2018 at 14:49

That does sound like a peculiar design. You pretty much created the problem you are trying to solve now.