STM CircleOS forum / Conflict between stop mode and iwdg?

gli · 2013-02-08 23:36:01

Hi,

I hope I can get some help on this.

It seems to me that you can not use stop mode and iwdg at the same time. The problem I have is that I enter slop mode and intend to stay there until it is waken up by an external interrupt, but if the iwdg is enabled, it will cause a reset and then an exit of the sleep mode. I can't reload watchdog counter in slop mode. Neither can I stop iwdg before entering into stop mode.

Any comments?

Greg

fjrg76 · 2013-05-21 22:53:44

What is the point when the STOP mode and the IWDG are enabled at the same time? Of course you can not reload the IWDG while in STOP mode 'cause the core has been stopped.

According to the RM:

The IWDG is best suited to applications which require the watchdog to run as a totally
independent process outside the main application, but have lower timing accuracy
constraints. For further information on the window watchdog, refer to Section 22 on page
465.

You might use the WWDG instead:

Advanced watchdog interrupt feature
The Early Wakeup Interrupt (EWI) can be used if specific safety operations or data logging
must be performed before the actual reset is generated. The EWI interrupt is enabled by
setting the EWI bit in the WWDG_CFR register. When the downcounter reaches the value
0x40, an EWI interrupt is generated and the corresponding interrupt service routine (ISR)
can be used to trigger specific actions (such as communications or data logging), before
resetting the device.

gli · 2013-05-24 21:56:14

Thank you for the comment on why anyone would need STOP and IWDG at the same time. But we have a special custom product that once built and sealed there is no physical access to reset the device if the firmware gets stuck. The product also requires it stay at lowest power possible most of the time The device will be woken up through an optical port by one of the EXITI pins. This optical port is also used for communications with external devices.

Since the firmware is sophisticated enough, we would like to have the DWG enabled. That is the reason we would like to have both STOP and DWG at the same time. I believe some other MCUs have this option.

hitesh53c · 2013-10-28 20:47:54

hey,
please help me to put LCD on stm32f103ve board into power saving mode?

jhnlmn · 2013-11-24 23:09:55

I have the same problem - previous developers of my FW solved it by performing reset before entering sleep. That killed the IWDG. But that also lost some important info, such as input edge detection in EXTI. So, by the time I enter sleep mode I already may have lost the wake up event. And I cannot use WWDG, as fjrg76 suggested, because max time for for WWDG is just few dozen ms, so it cannot be used as system wide watchdog (max time of IWDG may be many seconds).
So, I will continue using reset before sleep, even it will make my system buggy (it will loose input once in a while). But I just do not see any solution.
I wonder how other people solve this problem?

# 1 2013-02-08 23:36:01 Conflict between stop mode and iwdg?

Conflict between stop mode and iwdg?

# 2 2013-05-21 22:53:44 Conflict between stop mode and iwdg?

Re: Conflict between stop mode and iwdg?

# 3 2013-05-24 21:56:14 Conflict between stop mode and iwdg?

Re: Conflict between stop mode and iwdg?

# 4 2013-10-28 20:47:54 Conflict between stop mode and iwdg?

Re: Conflict between stop mode and iwdg?

# 5 2013-11-24 23:09:55 Conflict between stop mode and iwdg?

Re: Conflict between stop mode and iwdg?

Board footer