read back protection puts tag to high current consumption

[Sal]

Hi, I am seeing an issue where after enabling read back protection (rbp) on NRF52 and using sdk 12.1 the tag goes to state where it drains a lot of current.

command used: nrfjprog -f NRF52 --rbp ALL

I have used power profiler to check the behavior, current drain jumps to about ~1.5 mA, from ~120 uA. Since nrfjprog commands are disabled after rbp, issuing a reset command (nrfjprog -f NRF52 --reset) would not help the issue, rather increases the current consumption even higher to about ~3.5 mA (although I see an error message indicating recover command should be used to talk to the chip again, but still the command seems to succeed the first time around and increase current drain even more):

$ nrfjprog -f NRF52 --reset ERROR: The operation attempted is unavailable due to readback protection in ERROR: your device. Please use --recover to unlock the device.

The only way to recover is via a battery pull (pinreset, or debugreset commands also do not seem to fix the issue as the current drain stays high).

Can you please help explain why (and also under what conditions) the chip goes to this state (probably "debug state"?) and how can I recover without a battery pull. I would need to have the rbp enabled and it seems using rbp is only one way the chip could get into this high current drain mode.

**Please help explain other possible conditions that could lead to this high current drain mode.

Thanks.

[Stian Røed Hafskjold]

Yes, the chip enters debug mode, and needs to be reset. You can reset by using a pin reset: infocenter.nordicsemi.com/.../power.html. The PSELRESET registers need to be set, and the p21 pin must be routed out to the debugger. You can do a pin reset with nrfjprog --pinreset

[Sal]

I am using a Ubuntu vm to program chip and windows 7 to power profile (The commands are issued from Ubuntu therefore linux: JLinkExe).

Tried your suggestion on my custom board, still seeing the same issue (does not exit debug mode). Here is the logs and revision of jlink/nrfjprog:

$ nrfjprog -v
nrfjprog version: 9.7.1
JLinkARM.dll version: 6.20e

$ JLinkExe
SEGGER J-Link Commander V6.20e (Compiled Oct  6 2017 17:06:37)
DLL version V6.20e, compiled Oct  6 2017 17:06:32


Connecting to J-Link via USB...O.K.
Firmware: J-Link OB-SAM3U128-V2-NordicSemi compiled Jul 24 2017 17:30:12
Hardware version: V1.00
S/N: 681792490
VTref = 3.300V


Type "connect" to establish a target connection, '?' for help
J-Link>SWDSelect
Select SWD by sending SWD switching sequence.
Found SWD-DP with ID 0x2BA01477
J-Link>SWDWriteDP 1 0x04000000
Write DP register 1 = 0x04000000
J-Link>

I also have a board with pin reset connection you suggested earlier. Trying the same command on it would also not exit debug mode. Also tried just the pinreset command and it also seems to put the tag in the high current mode (very strange!). For your reference here are the command sequence:

1. Program tag
2. check the current drain and issue a reset to make sure: nrfjprog --reset
3. run pinreset and monitor the current nrfjprog --pinreset
4. the current drain jumps to around ~3 mA. This is even without rbp enabled.

I am currently trying to use the same setup as yours to eliminate any hw issues on my custom board. Attached please find the setup I am using to measure the current and issue commands (rbp/reset/etc.) at the same time (screenshot attached above).

1. The nrf52 dev kit is running the below hex file (top right dev kit). nRF5_SDK_12.1.0_0d23e2a\examples\ble_peripheral\ble_app_beacon\hex\ble_app_beacon_pca10040_s132.hex
2. It is powered via the devkit(nrf51) and ppk setup (buttom dev kit -- connected to windows 7 host).
3. A third dev kit (nrf51 -- top left -- connected to Ubuntu vm) is used to issue commands via the ribbon cable as shown on the screenshot. However, the commands are not directed to the NRF52 chip. Instead they are directed to the nrf51 kit (top left dev kit). (Please let me know if there is a jumper setup that would direct the command to the nrf52 kit. If the setup is not correct please share your setup).
4. On the ppk ui I see the average current about ~550uA (which application you are using that would give 2uA?)
5. Please note that this is the same setup I am using when using my custom board to measure current (here in the screenshot it is only replaced with NRF52 kit -- top right board).

Thanks.