Bootloader programming issue The flash is not erased

[ting²]

Hi everyone, I am using the nRF51822, I have an issue of programming the bootloader. It is said that the flash is not erased. But I just did an erase all before programming. Is there anyone who encountered the same issue? Thanks!

[Keton]

I'm having the same issue on one of my Rigado BMD300 based boards. It came preprogrammed with bootloader and demo code which ran ok. After erasing nothing can be programmed into it despite multiple erase all and recover commands that run without error. Other chips from the same batch program just fine so this may be a faulty chip.

[bjorn-spockeli]

If the device was running the demo code, then I doubt that its a faulty chip. Could you read out the flash after erasing the chip using the follwing command in nrfjprog

nrfjprog --memrd 0x0000 --n 262144 > flash_dump.txt

and then attach the flash_dump.txt to your question?

[Keton]

It appears that my board layout may be a problem. We've planned on using p0.21 as normal gpio and it turns out that cutting the trace leading to this pin allows us to program the nRF52. Please correct me if I'm wrong but default state of the chip after erase should be that reset on pin is disabled?

[bjorn-spockeli]

@keton : Yes, the PSELRESET[0] and PSELRESET[1] are set to 0xFFFFFFFF upon reset, i.e. no pin will have the nRESET function. However, please note that P0.21 is the only pin that can be used as the reset pin on the NRF52.

[Keton]

@bjorn-spockeli this may be true for the time when application is running but my experiments suggest that P0.21 should be left disconnected during interaction with J-Link, esp. during flashing. Otherwise various unexpected things happen. As I understand the documentation P0.21 should be ordinary GPIO unless PSELRESET registers are set. Please advise is that a correct interpretation. Maybe documentation should be clarified in that matter?