I installed the ESP EXCEPTION DECODER along with my Arduino IDE. When my sketch crashes with Exception 29, I take the stack trace and input it, but I can't understand its line references (they dont seem to point to my code).

Exception (29): epc1=0x4020ec84 epc2=0x00000000 epc3=0x00000000 excvaddr=0x00000000 depc=0x00000000

ctx: sys sp: 3ffffcd0 end: 3fffffb0 offset: 01a0

3ffffe70: 3fffb558 00000000 3fff197c fffffffb
3ffffe80: 3fff0ea0 3fff0ea0 00000000 4020fb20
3ffffe90: 00000000 00000000 0000001f fffffffb
3ffffea0: 3fff0ea0 00000000 3fff0e9c 4020ed35
3ffffeb0: 40000f68 3ffe93b4 3fff0e9c 402120ec
3ffffec0: 00000000 00000007 3fff197c 402137fa
3ffffed0: 3ffe93b4 3ffe93b4 3fff0e9c 4021211a
3ffffee0: ffffffff 3fff0e9c 3fff197c 4021463c
3ffffef0: 0100a8c0 3fffdcb0 3ffee960 00000030
3fffff00: 00000000 3fff0e9c 3fff197c 4021468f
3fffff10: 4020ffa8 3fff0afc 3fff0fc4 40100690
3fffff20: 40229e46 00000000 00000012 3fff0af8
3fffff30: 4020ffa8 3fff0afc 3ffe9348 4020ffb6
3fffff40: 40104d7e 948e6801 00000018 40210074
3fffff50: 3ffe9348 3ffed9fc 948e6801 00000000
3fffff60: 4022e654 3ffee928 3ffee950 60000600
3fffff70: 0fc612e0 3ffee950 3ffee928 4022e661
3fffff80: 4022e6a6 3fffdab0 00000000 3fffdcb0
3fffff90: 3ffee968 40000f65 3fffdab0 00000000
3fffffa0: 40000f49 3ffe96e8 3fffdab0 40000f49

0x4020fb20: tcp_abort at core/tcp.c line 544

0x4020ed35: netif_sta_status_callback at glue-lwip/lwip-git.c line 303

0x402120ec: netif_set_ipaddr at core/netif.c line 545

0x402137fa: dhcp_create_msg at core/ipv4/dhcp.c line 1825

0x4021211a: netif_set_addr_LWIP2 at core/netif.c line 584

0x4021463c: dhcp_release_LWIP2 at core/ipv4/dhcp.c line 1314

0x4021468f: dhcp_coarse_tmr at core/ipv4/dhcp.c line 423

0x4020ffa8: cyclic_timer at core/timeouts.c line 165

0x40100690: free at /home/tony/.arduino15/packages/esp8266/hardware/esp8266/2.4.1/cores/esp8266/umm_malloc/umm_malloc.c line 1739

0x4020ffa8: cyclic_timer at core/timeouts.c line 165

0x4020ffb6: cyclic_timer at core/timeouts.c line 171

0x40210074: sys_check_timeouts at core/timeouts.c line 351

How can I find ou what happens at address 0x4020ec84 and what line it points to?

  • 1
    use the latest esp8266 arduino core 2.5.2.
    – Juraj
    May 21, 2019 at 10:56
  • done. went in BOARDS MANAGER and upgraded core from 2.4.1 to 2.5.2 - what next?
    – tony gil
    May 21, 2019 at 16:41
  • upgraded, must wait for problem to occur (historically it has taken 16+ hours to manifest itself - memory might be an issue)
    – tony gil
    May 21, 2019 at 16:59
  • 1
    do you use String class to build strings and convert numbers?
    – Juraj
    May 21, 2019 at 17:36
  • 1
    – Juraj
    May 21, 2019 at 19:05


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