Hi, I'm wonder if it's possible to control watchdog on mbed ?

Regards

macc

Yes, but you'll have to do it yourself, there are no ready-made classes in mbed library.

It shouldn't be hard. What would make a good natural interface?

Something like:

Watchdog wd;      // create a watchdog
wd.feed(1.0);     // feed the watchdog with a specific timeout
wd.feed();        // re-feed the watchdog with the same timeout

I've not done a review of may watchdog architectures, but I can't believe they can't support something like that.

Simon

A good source of inspiration could be NXP's driver library. For example, here's what they have for the watchdog:

void WDT_Init (uint32_t ClkSrc, uint32_t WDTMode) Initial for Watchdog function Clock source = RTC , PCLK, IRC 
void WDT_Start (uint32_t TimeOut) Start WDT activity with given timeout value.
void WDT_Feed (void) After set WDTEN, call this function to start Watchdog or reload the Watchdog timer.
FlagStatus WDT_ReadTimeOutFlag (void) Read WDT Time out flag.
void WDT_ClrTimeOutFlag (void) Clear WDT Time out flag.
void WDT_UpdateTimeOut (uint32_t TimeOut) Update WDT timeout value and feed.
uint32_t WDT_GetCurrentCount (void) Get the current value of WDT.

P.S. I thought watchdog is supposed to be kicked, not fed? ;)

Wikipedia says:

• writing a “service pulse”
• "kicking the dog"
• “petting the dog”
• "feed the watchdog"
• "waking the watchdog"

I do wonder sometimes in these sorts of wikipedia listings whether it is more someone sitting down coming up with as many ideas of what they could imagine calling something, rather than what anyone actually calls it :)

I think I prefer kick, but why kicking a watchdog keeps him quiet I'm not sure.

I think it's like kicking the dog so that it keeps away and doesn't bite you :)

Here is a quick example that does something:

#include "mbed.h"

DigitalOut led(LED1);

class Watchdog {
public:
    void kick(float s) {
        LPC_WDT->WDCLKSEL = 0x1;                // Set CLK src to PCLK
        uint32_t clk = SystemCoreClock / 16;    // WD has a fixed /4 prescaler, PCLK default is /4 
        LPC_WDT->WDTC = s * (float)clk;         
        LPC_WDT->WDMOD = 0x3;                   // Enabled and Reset        
        kick();
    }
    
    void kick() {
        LPC_WDT->WDFEED = 0xAA;
        LPC_WDT->WDFEED = 0x55;
    }
};

Watchdog w;

int main() {
    printf("Hello World!\n");
    w.kick(2.5);

    int hang = 0;
    while(1) {
        printf("loop...\n");
        wait(0.1);
        
        if(hang == 10) {
            while(1);
        }

        w.kick();
        hang++;
    }
}

WatchdogExample

I'm sure it needs lots of refinement, but might be an interesting starting point.

Simon

Hi Igor,

In the stuff from the driver library, what are the units for timeout, PCLK cycles?

Thanks for reply.

Where are the NXP driver library ? When I'm traying to include :

#include "lpc17xx_wdt.h"

or  #include ""LPC1768/LPC17xx_wdt.h"

compiler complain "Cannot open source file ....".

The deeper question is how to use NXP driver library or other resources not beeing included into compiler

Regards

macc

Timeout is milliseconds. The library routine sets up the clock and converts the timeout value as necessary. Here's the code:

/********************************************************************//**
 * @brief         Set WDT time out value and WDT mode
 * @param[in]    clk_source select Clock source for WDT device
 * @param[in]    timeout value of time-out for WDT (us)
 * @return        None
 *********************************************************************/
uint8_t WDT_SetTimeOut (uint8_t clk_source, uint32_t timeout)
{

    uint32_t pclk_wdt = 0;
    uint32_t tempval = 0;

    switch ((WDT_CLK_OPT) clk_source)
    {
    case WDT_CLKSRC_IRC:
        pclk_wdt = 4000000;
        // Calculate TC in WDT
        tempval  = (((pclk_wdt) / WDT_US_INDEX) * (timeout / 4));
        // Check if it valid
        if ((tempval >= WDT_TIMEOUT_MIN) && (tempval <= WDT_TIMEOUT_MAX))
        {
            LPC_WDT->WDTC = tempval;
            return    SUCCESS;
        }

        break;

    case WDT_CLKSRC_PCLK:

        // Get WDT clock with CCLK divider = 4
        pclk_wdt = SystemCoreClock / 4;
        // Calculate TC in WDT
        tempval  = (((pclk_wdt) / WDT_US_INDEX) * (timeout / 4));

        if ((tempval >= WDT_TIMEOUT_MIN) && (tempval <= WDT_TIMEOUT_MAX))
        {
            CLKPWR_SetPCLKDiv (CLKPWR_PCLKSEL_WDT, CLKPWR_PCLKSEL_CCLK_DIV_4);
            LPC_WDT->WDTC = (uint32_t) tempval;
            return SUCCESS;
        }

        // Get WDT clock with CCLK divider = 2
        pclk_wdt = SystemCoreClock / 2;
        // Calculate TC in WDT
        tempval  = (((pclk_wdt) / WDT_US_INDEX) * (timeout / 4));

        if ((tempval >= WDT_TIMEOUT_MIN) && (tempval <= WDT_TIMEOUT_MAX))
        {
            CLKPWR_SetPCLKDiv (CLKPWR_PCLKSEL_WDT, CLKPWR_PCLKSEL_CCLK_DIV_2);
            LPC_WDT->WDTC = (uint32_t) tempval;
            return    SUCCESS;
        }

        // Get WDT clock with CCLK divider = 1
        pclk_wdt = SystemCoreClock;
        // Calculate TC in WDT
        tempval  = (((pclk_wdt) / WDT_US_INDEX) * (timeout / 4));

        if ((tempval >= WDT_TIMEOUT_MIN) && (tempval <= WDT_TIMEOUT_MAX))
        {
            CLKPWR_SetPCLKDiv (CLKPWR_PCLKSEL_WDT, CLKPWR_PCLKSEL_CCLK_DIV_1);
            LPC_WDT->WDTC = (uint32_t) tempval;
            return    SUCCESS;
        }
        break ;


    case WDT_CLKSRC_RTC:
        pclk_wdt = 32768;
        // Calculate TC in WDT
        tempval  = (((pclk_wdt) / WDT_US_INDEX) * (timeout / 4));
        // Check if it valid
        if ((tempval >= WDT_TIMEOUT_MIN) && (tempval <= WDT_TIMEOUT_MAX))
        {
            LPC_WDT->WDTC = (uint32_t) tempval;
            return    SUCCESS;
        }

        break;

// Error parameter
        default:
            break;
}

    return ERROR;
}

I made it to compile in the online compiler. Should be importable as library. Get links here: DriverLibrary For documentation see index.chm in the original package.

The code is quite sloppy, I had to fix tons of warnings and found a couple of bugs in the process, but don't assume there are none left.

Wow , I'm ipressed ! Good work.

Thanks for clear and detailed explanation.

macc

I wrote a watchdog class inspired by Simon's post that includes Reset and Interrupt operations.

But I can't seem to read the status of the reset to main to determine what happened: Power-on or Watchdog Timeout. Reading LPC_WDT->WDMOD yields 0. Seems that I am reading the wrong register.

Is this the correct register to read?

int main() {
 int ResetType = w.status();   // read watchdog to determine why we are here
// bool ResetType = w.status();   // read watchdog to determine why we are here
 

/*===========================================================
        status     Read Watchdog status
       
    This procedure reads the current Watchdog status to
    determine how we were reset.
 ==========================================================*/  

#if 0
    bool Watchdog::status() {            // read Status
         bool foo = (LPC_WDT->WDMOD & (1<<WDTOF)); // to get WDTOF flag
         LPC_WDT->WDMOD &= ~(1<<WDTOF); // reset status for next time
         return(foo);
    }
#endif   
    int Watchdog::status() {            // read Status
         int foo = LPC_WDT->WDMOD; // to get WDTOF flag
         LPC_WDT->WDMOD &= ~(1<<WDTOF); // reset status for next time
         return(foo);
    }

You appear to be reading the correct register (and I assume WDTOF is set to 2). Carrying on from Simon's example, I have:

#include "mbed.h"

// Simon's Watchdog example

class Watchdog {
public:
    void kick(float s) {
        LPC_WDT->WDCLKSEL = 0x1;                // Set CLK src to PCLK
        uint32_t clk = SystemCoreClock / 16;    // WD has a fixed /4 prescaler, PCLK default is /4 
        LPC_WDT->WDTC = s * (float)clk;         
        LPC_WDT->WDMOD = 0x3;                   // Enabled and Reset        
        kick();
    }
    
    void kick() {
        LPC_WDT->WDFEED = 0xAA;
        LPC_WDT->WDFEED = 0x55;
    }
};

Watchdog wdt;

// Watchdog service routine

void bad_dog(void)
{
    wdt.kick();    
    printf("Dog kicked\n");
}

int main() {
    Ticker          service;
    DigitalOut      heartbeat(LED1);
    unsigned long   wd_flag;
    int             count = 0;
    
    printf("Reset!\n");
    wd_flag = (LPC_WDT->WDMOD >> 2) & 1;
    printf("Watchdog caused reset: %s\n", (wd_flag > 0) ? "True" : "False");    
    wd_flag = (LPC_WDT->WDMOD >> 2) & 1;
    printf("Check watchdog cleared before clear: %s\n", (wd_flag == 0) ? "True" : "False");
    LPC_WDT->WDMOD &= ~(1 << 2);
    wd_flag = (LPC_WDT->WDMOD >> 2) & 1;
    printf("Check watchdog cleared after clear: %s\n", (wd_flag == 0) ? "True" : "False");
    
    wdt.kick(5.0);          // 5 second timeout on watchdog - to make it visible
    
    service.attach(&bad_dog, 2);
    while(1)
    {
        heartbeat = !heartbeat;
        wait(0.5);
        count++;
        if(count > 20)
            service.detach();   // Stop servicing watchdog, to force "bite"
    }
}

Reset!
Watchdog caused reset: False
Check watchdog cleared before clear: True
Check watchdog cleared after clear: True
Dog kicked
Dog kicked
Dog kicked
Dog kicked
Dog kicked
Reset!
Watchdog caused reset: True
Check watchdog cleared before clear: False
Check watchdog cleared after clear: True
Dog kicked
...

Thanks Jon,

I had created two methods as Reset and Interrupt. The Reset proc was ok, but the Interrupt procedure was not. Need to do a little more study here as I can see the WDTOF flag true at the interrupt entry but this gets cleared when I attempt to pass pass this onward as a Reset method with time as 0.

Thanks for the feedback!

What registers are available to pass information to the newly rebooted code.

i.e besides knowing if the 'dog' reset the machine can you pass any other flags.

This would be of help in providing information to the app, it could take into account that a sensor was providing faulty reading for example.

Thank you.

Sorry for the bad formatting of my former answer !

There are 5 registers in the RTC (LPC_RPC->GPREG0 to ...4) intended for this purpose. I tested this with a little change in the example of Simon Ford. I add two functions: getBU returns one RTC backup register setBU write a new value

The main test program increments this BU counter after each restart i = w.getBU(); printf("Hello World! this is nr %i\n",i); w.setBU(i+1); ...and the test was positive !

Robert

#include "mbed.h"
#include "LPC17xx.h"

DigitalOut led1(LED1),led2(LED2);
Serial pc(USBTX, USBRX);


class Watchdog {
// from // http://mbed.org/forum/mbed/topic/508/
public:
    void kick(float s) { //set the watchdog duration = s
        LPC_WDT->WDCLKSEL = 0x1;                // Set CLK src to PCLK
        uint32_t clk = SystemCoreClock / 16;    // WD has a fixed /4 prescaler, PCLK default is /4 
        LPC_WDT->WDTC = s * (float)clk;         
        LPC_WDT->WDMOD = 0x3;                   // Enabled and Reset        
        kick();
    }
    
    void kick() { //reset the watchdog
        LPC_WDT->WDFEED = 0xAA;
        LPC_WDT->WDFEED = 0x55;
    }
    void setBU(char x){
        LPC_RTC->GPREG0 = x;
    }
    char getBU(){
        return LPC_RTC->GPREG0;
    }
};

Watchdog w;

int main() {
    wait(0.2);
    led1=1;
    pc.baud(115200); //i
    int i;
    i = w.getBU();
    printf("Hello World! this is nr %i\n",i);
    w.setBU(i+1);
    w.kick(2.5);

    int hang = 0;
    while(1) {
        printf("loop...\n");
        wait(0.1);
        
        
        if(hang == 10) {
            led2=1;
            while(1);
        }

        w.kick();
        hang++;
    }
}

This code works great! Thank You...

Is there a way to capture on a reboot that the reboot was triggered by the Watchdog? Like, could w.setBU(1) be set if the watchdog engages and triggers a reboot? Then the bit could be read on the next startup...

Example (on Startup):

if(w.getBU() == 1){pc.printf("Rebooted By Watchdog...\n"); w.setBU(0);}

This is what I have done : Let us use one bit of this register: - when the programs starts , set this bit "on" - when the program stops in a normal way, set this bit "off" . I need a menu to stop the program because I use a electronic switch. The power-on occurs with a push-button. Then the microprocessor starts and a digital out sets the same mosfet to ground, maintaining the power-on status. The "off" menu releases this digital out and the power is off.

Now it is easy: if the program starts with the bit "on"...it is a restart from the watchdog. If the program starts with the bit "off"...it is a normal start.

This was done with a atmega128 but it is not the real answer to your precise question. The LPC 1768 is a powerfull beast: in the user manual look at 3.4.1 Reset Source Identification Register.(RSID) It is at the page 21 of UM10360 (your are lucky...there are 840 pages) The bit WDTR is set when ...a watchdog timeout occurs and this is the answer to your question (I hope ...) This should be the LPC_SC->RSID register. Try to return in the getBU - the backup registers, like my example return LPC_RTC->GPREG0; - the reset source LPC_SC->RSID

The compiler accepts this LPC_SC->RSID but I did not test further.

Robert

I recall that there are status register bits for the cause of reset: power-on, watchdog timeout, etc.

can we or can we not turn off the watchdog in LPC1768??

I believe its OFF by default

How can I get the above to work for the lpc11u24 ?

Cheers

Ceri

Thanks for the code,

a few problems ...

feed does not work, I cannot add it as:

feed();
WatchDog.feed();

or

Watchdog WD 


WD.feed()

additionaly, just using:

DigitalIn CtlAltDel(P0_1);
WatchDog (4.0);

while (1)
{
    // Flash LED's for 3.5 seconds ..

    if (!CtlAltDel)
    {
       LED's = ON;
       wait (6);
    }

}

the LPC11U24 does reset, but the DFU/ISP pin is ignored :( and just runs normal code.

As my main reason was to jump to boot-loader with a single button.

I would of expected this to happen ? or am I wrong ?

Cheers

Ceri

Thanks The above works,

but still not able to get LPC11U24 to reset into DFU/ISP Bootloader.

Thanks

Ceri

Many thanks again,

sounds a bit strange ?

my original idea was to force a reset, but I don't know the command.

Ceri

Found out ho to do it :)#

NVIC_SystemReset();

works, press ISP button ... DFU/ISP drive appears

MAGIC .

Ceri

I've been trying to get WDT on LPC1768 to work in "debug mode", that is, I don't want WDT to do a reset but to just interrupt. I've used Simon's base code, and the WDT timer fires once (LED lights), but I think i'm stuck in the wdt_isr. it's not clear from the reference manual, how one clears the WDT interrupt flag, so the WDT timer can fire again.

any one have an example of WDT running in "non reset" mode?

Not all NXP watchdog timers can do this. You should check in the reference manual if it is capable of doing this, some can only do an interrupt once.

The LPC11u24 can do it as you want, here is an example of that: https://developer.mbed.org/users/Sissors/code/WakeUp/file/9d355da2770e/Device/WakeUp_LPC11u24.cpp. If the LPC1768 has the same WDT you can implement something similar.