I was trying to program the nRF52_Sensor_R40 using OpenOCD + STLink, but without luck.
Then I decided to use my JLink EDU to erase the nRF52 and it worked! \o/
I powered the nRF52_Sensor_R40 with 3.3V connected the GND to JLink’s pin 20, the 3.3V to JLink’s pin 1, the SWDCLK to JLink’s pin 9 and SWDIO to JLink’s pin 7.
$ sudo JLinkExe -if SWD SEGGER J-Link Commander V6.80d (Compiled Jun 26 2020 17:19:52) DLL version V6.80d, compiled Jun 26 2020 17:19:40 Connecting to J-Link via USB...O.K. Firmware: J-Link ARM V8 compiled Nov 28 2014 13:44:46 Hardware version: V8.00 J-Link>con Please specify device / core. : NRF52832_XXAA Type '?' for selection dialog Device> Specify target interface speed [kHz]. : 4000 kHz Speed> Device "NRF52832_XXAA" selected. Connecting to target via SWD InitTarget() start Device will be unsecured now. InitTarget() end Found SW-DP with ID 0x2BA01477 Unknown DP version. Assuming DPv0 Scanning AP map to find all available APs AP: Stopped AP scan as end of AP map has been reached AP: AHB-AP (IDR: 0x24770011) AP: JTAG-AP (IDR: 0x02880000) Iterating through AP map to find AHB-AP to use AP: Core found AP: AHB-AP ROM base: 0xE00FF000 CPUID register: 0x410FXXXX. Implementer code: 0x41 (ARM) Found Cortex-M4 r0p1, Little endian. FPUnit: 6 code (BP) slots and 2 literal slots CoreSight components: ROMTbl @ E00FF000 ROMTbl: E000E000, CID: B105E00D, PID: 000BB00C SCS-M7 ROMTbl: E0001000, CID: B105E00D, PID: 003BB002 DWT ROMTbl: E0002000, CID: B105E00D, PID: 002BB003 FPB ROMTbl: E0000000, CID: B105E00D, PID: 003BB001 ITM ROMTbl: E0040000, CID: B105900D, PID: 000BB9A1 TPIU ROMTbl: E0041000, CID: B105900D, PID: 000BB925 ETM Cortex-M4 identified. J-Link>