nRF52840 Errata 187 for SDK 15.0.0

[joer55]

Hello:

I am working on a USB bootloader project.  I am running into the issue where the USB will not boot on first start up but boots following this.  I read some of the previous comments on the issue. On thing I am seeing:  The code below does not return True for our implementation. It would fix the issue if did return True. This is the Errata 187 detection code.

static inline bool nrf_drv_usbd_errata_type_52840_fp1(void) {

   return ( nrf_drv_usbd_errata_type_52840() &&
    ( ((*(uint32_t *)0xF0000FE8) & 0xF0) == 0x20 ) &&    /// use to be 0x10
    ( ((*(uint32_t *)0xF0000FEC) & 0xF0) == 0x00 ) );

}

I am seeing the value 0x30 returned from register 0xF000_0FE8 (instead of 0x10 or 0x20).  Is it ok to patch the  nrf_drv_usbd_errata_type_52840_fp1() function with 0x30 instead of 0x20?

Thanks,

joer55

[ovrebekk]

Hi Joe

What you are seeing is an issue in the errata file, where future revisions default to not implementing any workarounds. 

In later SDK versions this is changed, and a function called nrf_errata_xxx will be called instead, to verify which workarounds should be applied or not.

For reference here is the implementation for errata 187:

static bool nrf52_errata_187(void)
{
    #ifndef NRF52_SERIES
        return false;
    #else
        #if defined (NRF52820_XXAA) || defined (DEVELOP_IN_NRF52820)\
         || defined (NRF52833_XXAA) || defined (DEVELOP_IN_NRF52833)\
         || defined (NRF52840_XXAA) || defined (DEVELOP_IN_NRF52840)
            uint32_t var1 = *(uint32_t *)0x10000130ul;
            uint32_t var2 = *(uint32_t *)0x10000134ul;
        #endif
        #if defined (NRF52840_XXAA) || defined (DEVELOP_IN_NRF52840)
            if (var1 == 0x08)
            {
                switch(var2)
                {
                    case 0x00ul:
                        return false;
                    case 0x01ul:
                        return true;
                    case 0x02ul:
                        return true;
                    case 0x03ul:
                        return true;
                }
            }
        #endif
        #if defined (NRF52833_XXAA) || defined (DEVELOP_IN_NRF52833)
            if (var1 == 0x0D)
            {
                switch(var2)
                {
                    case 0x00ul:
                        return true;
                    case 0x01ul:
                        return true;
                }
            }
        #endif
        #if defined (NRF52820_XXAA) || defined (DEVELOP_IN_NRF52820)
            if (var1 == 0x10)
            {
                switch(var2)
                {
                    case 0x00ul:
                        return true;
                    case 0x01ul:
                        return true;
                    case 0x02ul:
                        return true;
                }
            }
        #endif
        return false;
    #endif
}

As a quick fix you can change the code to ensure that errata 187 is applied to your device, yes. 

Best regards
Torbjørn

[joer55]

Thanks for the very helpful and complete response, much appreciated.

Joer55

[ovrebekk]

You welcome Joe, the best of luck with your project