IWDG short period (125 us) problem

[Rub�n Acerete Halli]

Posted on February 23, 2017 at 13:04

Hello,

We are developing a PV converter and we have choose an STM32F407VGT microcontroller in order to controlling its power electronics and communications. 

We are using the

♯

in order to ensuring that the software works properly and if not reset the system and initialize in a safe state. Mainly stopping the PWM modules and stop triggering the Mosfets. We would like configuring the IWDG at minimum period (125us). We carries out the IWDG reset in a timer (TIM2) update event interrupt each 50us. For reseting de WDG we are using the HAL function HAL_IWDG_Refresh(&hiwdg). Following is the IWDG initialization code:

hiwdg.Instance = IWDG;

hiwdg.Init.Prescaler = IWDG_PRESCALER_4;

hiwdg.Init.Reload = 0;

if (HAL_IWDG_Init(&hiwdg) != HAL_OK)

{

  Error_Handler();

}

We have tested 3 different values for hiwdg.Init.Reload, 0, 1, and 2. If we use 0 or 1 the systems restarts continuously. If we use 2 the watchdog works, but four application the watching time is too long and produce that some converter components could explode. How can we configuring the IWGD in order to having a WD period of 125us as told in the manual reference?

#iwdg #stm-32 #stm32f407 #problem

[Rub�n Acerete Halli]

Posted on February 24, 2017 at 09:41

I think that I am already doing it. because the RCC initializacion function test de return value. I will attach the whole code below.

[AVI-crak]

Posted on February 24, 2017 at 10:59

Then it is necessary to use more predictable mechanism of protection, on WWDG (a step from PCLK) + NMI_Handler ().

In this case there is a possibility of correct end of an emergency. Iron dumping - it isn't always ideal. Sometimes it is required to establish quickly legs мк in a necessary state which differs from dumping.

NMI_Handler () - all timers (except a dog) will automatically stop. It is impossible to work normally further already, it is necessary to finish correctly operation of the device + the ravine of an event on the independent carrier.

WWDG - a step from PCLK + normal interruption in which it is possible to finish accurately work of a cycle forcibly - transfer of a task to other prepared address, or in a forehead - start of an emergency task. For example the stop of the engine can lasts minutes and more. It is necessary to hold мк to a full stop of the engine, otherwise there can be problems.

It is simple to stamp a huge number of a code in interruption - it won't turn out. All environment is simpler to kill (this interruption very strong) - and to start only resolved. The stop of timers and installation of legs мк in a safe state is the simplest and bystry, remains in the interruption.

[Rub�n Acerete Halli]

Posted on February 24, 2017 at 14:20

I will try implement the WWDG but the IWGD cotinues existing and I do not understnad Why. Maybe It is a documentation error. I do not. 

[AVI-crak]

Posted on February 24, 2017 at 16:20

There are no documentation errors, there is not a full understanding.

IWGD - is intended for fatal cumulative errors when several physical devices of the periphery + an error of a program code, hangup on the data bus or to that similar can fail as avalanche directly. In this case helps only rest.

WWDG is intended for detection of errors of a program code, more precisely than incorrect distribution of machine time. As a rule when actuating similar interruption, мк works operationally: all data buses, all periphery and so on. Just instead of computation necessary at present - мк it was busy with some nonsense absolutely not necessary at this moment. And as a result - didn't manage to execute a basis cycle.

WWDG use as is - doesn't give security blanket. It is necessary to track the PLL generator, for its monitoring there is a separate interruption.

In case of PLL failure - the processor doesn't execute complete reset, but all timers pass into an inactive status. It is feeble protection if the logical unit on a timer output at rest is required from you.

[Rub�n Acerete Halli]

Posted on February 24, 2017 at 18:26

Ok Thank you very much for the detailed explanation. I will try the WWGD. I did not know that if the PLL fall the PWM modules stops in a safe way.