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AWR1843: AWR1843 with external Watchdog

saber ragab1
Expert 1350 points
Part Number: AWR1843

We need to add external watchdog for safety reasons, So we have several questions:

1- Is it possible to use external watchdog with AWR1843 chip?

2- How the flash bootloader will handle refreshing the watchdog in that case? 

3- Are their any constrains for using the external watchdog (timing , specific part number, ....)?

  • 0
    TI__Guru 69990 points

    Hi Saber,

    1. Yes, it is possible to use external watchdog with AWR1843. Mostly external watchdog needs to be fed by AWR device via an interface (SPI/I2C/GPIO). So on AWR1843 you need to implement a logic to interface with external PMIC/External_Host (having external watchdog). 

    2. Handling external watchdog will be responsible for the application running on AWR device. So deivce's bootloader is independent of controlling Ext.WDT.

    3. There is no dependency on controlling ext.WDT on part no.

    Note- Here assumption is that external WDT is running on ext. PMIC or MCU where AWR device is feeding to that WDT at a time interval.

    TI LP8770 PMIC has external WDT feature which you can use with AWR1843.

    Regards,

    Jitendra

  • 0 in reply to Jitendra Gupta
    Expert 1350 points

    Hi Jitendra,

    Thanks for your reply.

    My concern is during loading the program code and during flashing, the watchdog already is running after power up and the flash boat-loader will not refresh it, So we have to design the HW to disable the watchdog after power up and the application enable it is that the case or there is another solution. 

    Thanks in advance

  • 0 in reply to saber ragab1
    TI__Guru 69990 points

    Hi,

    Even though there is watchdog enabled in bootloader, bootloader will be held WDT in reset while switching to application. That means when application starts running watchdog will not be active, application needs to activate it with required configuration set.

    Based on this understanding could you specify, why do you need External Watchdog? (your last reply is not clear to explain reason to use Ext WDT).

    Regards,

    Jitendra

  • 0 in reply to Jitendra Gupta
    Expert 1350 points

    Hi Jitendra,

    you are taking about the internal watchdog but our project is safety level which requires external watchdog not internal one, So the external WD can't be disabled by software during bootloading. It means that to avoid WD reset, the software has to finish bootloading before WD reset.

    the question is now How much time (worst case) AWR1843 needs for bootloading, we can then meet that time requirement by changing the WD timeout value.  

    Waiting your soon answer
    Thanks,
  • 0 in reply to saber ragab1
    TI__Guru 69990 points

    Hi,

    Here is the boot time based on image size for GP (non HS device).

    GP Image (non HS device)

    Image Size(bytes)

    344964

    614400

    Boot time (cycles)

    7275615

    12958273.49

    Boot time (ms)

    36.37808

    64.79136745

    Based on your application size you can calculate back the application boot time and change the WD timeout accordingly.

    Regards,

    Jitendra