I put by XMC4500 in a state where OpenOCD was unable the communicate with it:
$ sudo openocd -f board/xmc4500-relax.cfg -c init -c "reset halt" -c "flash write_image erase nuttx.bin 0x0c000000" Open On-Chip Debugger 0.10.0+dev-00172-g7719e96 (2017-11-12-09:13) Licensed under GNU GPL v2 For bug reports, read http://openocd.org/doc/doxygen/bugs.html adapter speed: 4000 kHz cortex_m reset_config sysresetreq adapter speed: 1000 kHz Info : No device selected, using first device. Info : J-Link Lite-XMC4000 Rev.1 compiled Apr 2 2015 18:25:20 Info : Hardware version: 1.00 Info : VTarget = 3.300 V Info : clock speed 1000 kHz Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Error: Could not initialize the debug port Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Info : SWD DPIDR 0x2ba01477 Error: Could not initialize the debug port Error: Target not examined, reset NOT asserted! in procedure 'reset' in procedure 'ocd_bouncer'
What happened?
I just changed BOARD_SYSDIV :
# define BOARD_SYSDIV 0
But in clockconfig.c it does:
/* Setup fSYS clock */ regval = (BOARD_ENABLE_PLL << SCU_SYSCLKCR_SYSSEL); regval |= SCU_SYSCLKCR_SYSDIV(BOARD_SYSDIV); putreg32(regval, XMC4_SCU_SYSCLKCR);
SCU_SYSCLKCR_SYSDIV is defined this way:
# define SCU_SYSCLKCR_SYSDIV(n) ((uint32_t)((n)-1) << SCU_SYSCLKCR_SYSDIV_SHIFT)
So, it wrote 0xffffffff to SCU_SYSCLKCR register. 
Then I tried to flash using JLinkExe from Segger, but it also didn’t work:
$ JLinkExe -if SWD SEGGER J-Link Commander V6.14h (Compiled May 10 2017 18:39:45) DLL version V6.14h, compiled May 10 2017 18:39:37 Connecting to J-Link via USB...O.K. Firmware: J-Link Lite-XMC4000 Rev.1 compiled Apr 2 2015 18:25:20 Hardware version: V1.00 S/N: 551014400 VTref = 3.300V Type "connect" to establish a target connection, '?' for help J-Link>connect Please specify device / core. : XMC4500-1024 Type '?' for selection dialog Device> Specify target interface speed [kHz]. : 4000 kHz Speed> Device "XMC4500-1024" selected. Performing XMC4500 connection sequence. No AP preselected. Assuming that AP[0] is the AHB-AP AP-IDR: 0x24770011, Type: AHB-AP AHB-AP ROM: 0xE00FF000 (Base addr. of first ROM table) Found Cortex-M4 r0p1, Little endian. FPUnit: 6 code (BP) slots and 2 literal slots CoreSight components: ROMTbl[0] @ E00FF000 ROMTbl[0][0]: E000E000, CID: B105E00D, PID: 000BB00C SCS ROMTbl[0][1]: E0001000, CID: B105E00D, PID: 003BB002 DWT ROMTbl[0][2]: E0002000, CID: B105E00D, PID: 002BB003 FPB ROMTbl[0][3]: E0000000, CID: B105E00D, PID: 003BB001 ITM ROMTbl[0][4]: E0040000, CID: B105900D, PID: 000BB9A1 TPIU ROMTbl[0][5]: E0041000, CID: B105900D, PID: 000BB925 ETM Cortex-M4 identified. J-Link>loadbin ./nuttx.bin 0 Downloading file [./nuttx.bin]... Writing target memory failed.
Fortunately the “erase” command worked:
J-Link>erase Erasing device (XMC4500-1024)... Comparing flash [100%] Done. Erasing flash [100%] Done. Verifying flash [100%] Done. J-Link: Flash download: Total time needed: 22.650s (Prepare: 0.041s, Compare: 0.000s, Erase: 22.604s, Program: 0.000s, Verify: 0.000s, Restore: 0.004s) Erasing done.
But even after the flash erase the programming is not working:
J-Link>loadbin ./nuttx.bin 0 Downloading file [./nuttx.bin]... Writing target memory failed. J-Link>
Then I decided to try OpenOCD again:
$ sudo openocd -f board/xmc4500-relax.cfg Open On-Chip Debugger 0.10.0+dev-00172-g7719e96 (2017-11-12-09:13) Licensed under GNU GPL v2 For bug reports, read http://openocd.org/doc/doxygen/bugs.html adapter speed: 4000 kHz cortex_m reset_config sysresetreq adapter speed: 1000 kHz Info : No device selected, using first device. Info : J-Link Lite-XMC4000 Rev.1 compiled Apr 2 2015 18:25:20 Info : Hardware version: 1.00 Info : VTarget = 3.300 V Info : clock speed 1000 kHz Info : SWD DPIDR 0x2ba01477 Info : xmc4500.cpu: hardware has 6 breakpoints, 4 watchpoints Info : accepting 'telnet' connection on tcp/4444
And using telnet I tried to send the reset command:
$ telnet 127.0.0.1 4444 Trying 127.0.0.1... Connected to 127.0.0.1. Escape character is '^]'. Open On-Chip Debugger > reset halt timed out while waiting for target halted TARGET: xmc4500.cpu - Not halted in procedure 'reset' in procedure 'ocd_bouncer' Halt timed out, wake up GDB. >
At this moment I thought my board could be damaged, but I decided to try to flash it anyway:
> flash write_image erase nuttx.bin 0x0c000000 auto erase enabled Cannot communicate... target not halted. auto_probe failed
Hmm, let to test only “halt” instead of “reset halt” :
> halt target halted due to debug-request, current mode: Thread xPSR: 0x41000000 pc: 0x000000e6 msp: 0x2000ff3c
Good, now let to try again:
> flash write_image erase nuttx.bin 0x0c000000 auto erase enabled Clearing flash status Clearing flash status wrote 81920 bytes from file nuttx.bin in 17.523651s (4.565 KiB/s)
Very good, my board is live again!
Alan C. Assis 