I never managed to reproduce the Core Dump but I found this : https://github.com/pycom/pycom-micropython-sigfox/commit/3f690a5733d31ff938aad6219c498f7d1bf98346 A bug fix, the issue was not resolved in the version I used. This issue could explain the core dump I encountered. The issue is fixed in the last beta version (v1.20.3.b3) and in the last release (1.20.2.r4) of the firmware.

Hi, I believe you are experiencing the same issues as discussed here: https://forum.pycom.io/topic/5765/loadprohibited-core-panic-when-initialize-wlan Can you review the discussion? There are of course slight differences between the antennas etc. on the boards (manufacturing tolerances etc) and doing a full erase using the update firmware tool might help in that regard. Let me know!

It seems that the FTDI chip I was using started to brown out. I switched to external power with a DC supply and everything is back to normal. I should've tried that first. I didn't even think of it since for the first couple of weeks the FTDI chip had no issues supplying sufficient power. Regardless, thank you very much for your help @robert-hh

@jmarcelino The only thing connected during update is PyTrack module which I use to connect USB.

@jcaron - thanks

@robert-hh Concurrent access was my first idea too. To test it: I erased the flash to standard boot and main. Then I preloaded the SD with data. Re-ran the FTP test and it still had the same crashes. Using the FTP server on the device is for me is the easiest way. Otherwise I would need to create a Timer to upload data at regular intervals. To keep data transfer low I would need keep the intervals long avoiding me to have the flexibility of choosing which data I want to download and when. To be honest, I'm a bit disappointed by the eagerness of pycom to attack this problem. The same with my other crash report.

I've merged what was comprehensible: ets Jun 8 2016 00:22:57 rst:0xc (SW_CPU_RESET),boot:0x17 (SPI_FAST_FLASH_BOOT) coUMP END ================= Rebootin0,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00 mx17 (SPI_FAST_FLASH_BOOT) configsip: 0, SPIWP:0xee clk_drv:0x0:1060 load:0x4009fa00,len:0 ho 12 tail 0 room 4 load:0x4009fode:DIO, clock div:1 load:0x3fff9028,len:8 load:0x3fff9030,lenabort() was called at PC 0x4008dbb4 on core 1 Backtrace: 0x4a00,len:14096 entry 0x400a05e0 x40083c16:0x3ffd42f0 0x40083cb3:0x3ffd4320 0x4015ea88:0x3ffd437008e05f:0x3ffd4280 0x4008e090:0x3ffd42a0 0x4008dbb4:0x3ffd42c0 03f0 0x400dce42:0x3ffd4430 ================= CORE DUMP START 0 0x4015d95b:0x3ffd4390 0x4014d4d1:0x3ffd43d0 0x400e8a2c:0x3ffd4T+JBAAALFP8PyxT/D+8RP0/JFP8PxQAAAAAAAAAAAAAALxE/T8AAAAA BQAAAL================= Connecting on /dev/cu.usbmodemPy343431... /Users/danicampora/Code/Espressif/IDF/esp-idf-20180112/componena00,len:14096 entry 0x400a05e0 bort() was callea at PC 0xs008aaa8 on cor0x00 Backtrace: 0x40ts/freertos/./queue.c:718 (xQueueGenericSend)- assert failed! a4015d282:0x3ffd3bb0 0x4015d41a:0x3ffd3bd0 0x40155916:0x3ffd3c00 0x4014e3ec:0x3ffd3c20 ====x3ffd3b50 0x4008aaa8:0x3ffd3b70 0x============= HC0AAA4AAABsAQAA BFP9P3A6/T+wPP0/ oDn9P1A8/T+N 0x4014e3ec:0x3ffd3c20 ================= CORE DUMP END ================= Rebooting... ets Jun 8 2016 00:22:57 rst:0xc (SW_CPU_RESET),boot:0x12 (SPI_FAST_FLASH_BOOT) configsip: 0, SPIWP:0xee clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00 mode:DIO, clock div:1 load:0x3fff9028,len:8 load:0x3fff9030,len:1060 load:0x4009fa00,len:0 ho 12 tail 0 room 4 load:0x4009fa00,len:14096 entry 0x400a05e0 abort() was called at PC 0x4008dbb4 on core 1 Backtrace: 0x4008e05f:0x3ffd4280 0x4008e090:0x3ffd42a0 0x4008dbb4:0x3ffd42c0 0x40083c16:0x3ffd42f0 0x40083cb3:0x3ffd4320 0x4015ea88:0x3ffd4370 0x4015d95b:0x3ffd4390 0x4014d4d1:0x3ffd43d0 0x400e8a2c:0x3ffd43f0 0x400dce42:0x3ffd4430 ================= CORE DUMP START ================= Looks like this line will provide you more infos: Backtrace: 0x40ts/freertos/./queue.c:718 (xQueueGenericSend)- assert failed!

I suffer the same error with the new firmware version (1.10.2.b1). It seems they have not solved it until now... Have you found any solution?+ Thanks

if the error code changes it certainly is another error. No clue what -1 means, sorry.