sd_softdevice_enable does not return

[wouchida]

On one of our products, we are experiencing approximately 4% failures during production.  I traced the problem to be caused by function sd_softdevice_enable not returning.  This problem does not occur if I have a Segger JTAG probe connected or if the internal LF 32 KHz RC oscillator is used instead of the external crystal.  But with the external 32 KHz (20 ppm) crystal oscillator, about 4% of boards do not return from the sd_softdevice_enable function.  On the problem boards, our hardware engineers believe that this LF external oscillator is starting up normally.  They do not observe any startup differences between a good board or a bad board.  I would like to know the reasons why the function sd_softdevice_enable might not return.

[Kenneth]

All variants of the nRF82832 can have this issue (for instance it may vary over temperature), and thereby all applications running on the nRF52832 should apply this workaround yes.

Best regards,
Kenneth 

[eiadj]

Kenneth,

Ok, we have a different version of the product which essentially the same circuit with a different PCB layout and mechanical enclosure - we have NOT observed the issue with that product. Any idea's why?

With the product experiencing failures, we are seeing around 4% of units impacted - does that make sense based on Nordics data on this issue? Some context hear will help us understand is errata_108 is responsible for all of our issues or if there is a second effect we missing.

Can this issue spread with the working boards (Is errata_108 susceptibility something that could increases with usage time)? This will help dictate how we deal with existing inventory that already has firmware installed.

Thanks,

Eiad Jandali

[Hung Bui]

Hi Eiad, 

 

Kenneth is on vacation so I will try to help. 

As far as I know, your 4% error rate is in the ballpark of with what we observed. We recommend to implement the errata fix in all of your product.

Of the "working product" you have now, if it's working properly it doesn't mean that the chip doesn't have the issue, but it's possible that the corrupted memory is at a location that it doesn't affect the current normal operation of the device , at this moment. It can be guaranted that it will always works fine in the future. 

[wouchida]

Questions:
1. I assume that for errata 108, the following code segments from a later SDK can be used. Is this correct?

2. Currently, we are using nRF52832 chip, revision Rev 1 (QFAA-B00) and will be eventually transitioning to Rev 2 (QFAA-E00).  Will the below fix and the errata fixes for SDK_11 still work for the Rev 2 hardware?  In other words, will the hardware version check still be satisfied for to Rev 2 hardware?

/* Workaround for Errata 108 "RAM: RAM content cannot be trusted upon waking up from System ON Idle or System OFF mode" found at the Errata document for your device located at infocenter.nordicsemi.com/ */
if (errata_108()){
        *(volatile uint32_t *)0x40000EE4 = *(volatile uint32_t *)0x10000258 & 0x0000004F;
}

static bool errata_108(void)
{
    if ((((*(uint32_t *)0xF0000FE0) & 0x000000FF) == 0x6) && (((*(uint32_t *)0xF0000FE4) & 0x0000000F) == 0x0)){
        if (((*(uint32_t *)0xF0000FE8) & 0x000000F0) == 0x30){
            return true;
        }
        if (((*(uint32_t *)0xF0000FE8) & 0x000000F0) == 0x40){
            return true;
        }
        if (((*(uint32_t *)0xF0000FE8) & 0x000000F0) == 0x50){
            return true;
        }
    }

    return false;
}

Thanks,

Wayne

[Hung Bui]

Hi Wayne, 

Yes, it's the correct workaround. 

The errata is remained on Rev2 and the above code can be used for Rev 2 as well.