Nordic nRF52840 flash readout is inconsistent.

RE: Nordic nRF52840 flash readout is inconsistent.

Jørgen Holmefjord — Tue, 11 Jul 2023 14:18:07 GMT

[quote user="David-Enthoven"]we are using a segger J-link Compact[/quote]

How is the J-Link connected to the nRF52840? Please specify all pins/signals in use.

[quote user="David-Enthoven"]We have not had the chance yet due to some equipment being temporarily unavailable, soonest that we can do this test will be Thursday[/quote]

Please get the signals checked as soon as you have the equipment available.

[quote user="David-Enthoven"]We are running it on 3V3 lab supply (isolated from all other power on the board) and the SWD signal level is also 3V3 as far as we know.[/quote]

Have you tested other supply voltage levels if your board can handle that? Do they show same symptoms? The J-Link BASE Compact should support interface voltage levels between 1.2V to 5V on the SWD signal, given that the connections are done correctly, but would be good to get this confirmed.

[quote user="David-Enthoven"]I want to re-emphasize that this problem only near-consistently occurs on just 2 of the 5 boards.[/quote]

I noticed this, and it is also an indication to me that the signal integrity could be the source of this issue. Chip to chip variations in voltage of logic level of GPIO signals can cause marginal failures on some chips while others are working correctly, if the signal level is just below the expected threshold.

RE: Nordic nRF52840 flash readout is inconsistent.

David-Enthoven — Tue, 11 Jul 2023 12:02:44 GMT

Hi Jorgen,

we are using a segger J-link Compact
Our board is custom but our design is identical to configuration 5 w/o USB and NFC
We have not had the chance yet due to some equipment being temporarily unavailable, soonest that we can do this test will be Thursday
We are running it on 3V3 lab supply (isolated from all other power on the board) and the SWD signal level is also 3V3 as far as we know.

I want to re-emphasize that this problem only near-consistently occurs on just 2 of the 5 boards.

Kind Regards,
David Enthoven

RE: Nordic nRF52840 flash readout is inconsistent.

Jørgen Holmefjord — Tue, 11 Jul 2023 11:45:11 GMT

Hi,

What kind of debugger/programmer are you using?
Are you testing this on a custom board?
Have you looked at the SWD signals with a scope/logic analyzer? Since you get different readouts from the same chip after multiple tries, this seems to indicate a problem with the signal integrity.
What supply voltage are you running the device on? Is the signal level of the SWD lines at the same level as the supply voltage?

Best regards,
Jørgen