COM Port Disconnects and Always Goes Into Bootloader Mode

greenboba · July 11, 2021, 4:08pm

Hello, my Arduino NB MKR1500 always goes into bootloader mode by itself after uploading a sketch.

In Windows 10 Device Manager (with viewing hidden devices enabled), I can see both COM ports which the MKR1500 uses, COM3 and COM4 (COM4 is the bootloader). When I double-tap the reset button on-board, the MKR1500 switches to bootloader, which is the intended behaviour. When I only tap the reset button once, the MKR1500 switches to COM3, the other port.

However, the problem is when I upload a sketch. When I upload to the MKR1500 using COM3, it compiles and uploads the sketch, but after around 5 seconds the board makes a disconnect & reconnect sound and goes into bootloader mode by itself, using COM4. This behaviour happens on more complex sketches such as MKRNB examples, but also on simple sketches such as "Blink" and "BareMinimum". On sketches that use the serial monitor, I see some text on COM3, but once it switches to COM4 the sketch just seems to "stop working". When this happens, if I switch the serial monitor to COM4, the output is empty as well.

Sometimes, when the board is connected to COM4 and I hit the reset button once to change over to COM3, the Arduino will change after around 5 seconds to COM4 again.

I've tried switching USB cables and protocols (USB 3.0 and 2.0) which did not make a difference. I also tried reinstalling the Arduino IDE and board drivers. Another thing I tried is, while the Arduino is disconnected from the PC, holding down the reset button, plugging it in and releasing the reset button, which didn't seem to change anything either.

Thank you for any help.

Here is the compile/upload output in the IDE for the "Blink" sketch:

C:\Program Files (x86)\Arduino\arduino-builder -dump-prefs -logger=machine -hardware C:\Program Files (x86)\Arduino\hardware -hardware C:\Users\mattr\AppData\Local\Arduino15\packages -tools C:\Program Files (x86)\Arduino\tools-builder -tools C:\Program Files (x86)\Arduino\hardware\tools\avr -tools C:\Users\mattr\AppData\Local\Arduino15\packages -built-in-libraries C:\Program Files (x86)\Arduino\libraries -libraries C:\Users\mattr\OneDrive\Documents\Arduino\libraries -fqbn=arduino:samd:mkrnb1500 -vid-pid=2341_8055 -ide-version=10815 -build-path C:\Users\mattr\AppData\Local\Temp\arduino_build_126111 -warnings=none -build-cache C:\Users\mattr\AppData\Local\Temp\arduino_cache_16133 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.arduinoOTA.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\arduinoOTA\1.2.1 -prefs=runtime.tools.arduinoOTA-1.2.1.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\arduinoOTA\1.2.1 -prefs=runtime.tools.CMSIS-Atmel.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\CMSIS-Atmel\1.2.0 -prefs=runtime.tools.CMSIS-Atmel-1.2.0.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\CMSIS-Atmel\1.2.0 -prefs=runtime.tools.arm-none-eabi-gcc.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\arm-none-eabi-gcc\7-2017q4 -prefs=runtime.tools.arm-none-eabi-gcc-7-2017q4.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\arm-none-eabi-gcc\7-2017q4 -prefs=runtime.tools.CMSIS.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\CMSIS\4.5.0 -prefs=runtime.tools.CMSIS-4.5.0.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\CMSIS\4.5.0 -prefs=runtime.tools.openocd.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\openocd\0.10.0-arduino7 -prefs=runtime.tools.openocd-0.10.0-arduino7.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\openocd\0.10.0-arduino7 -prefs=runtime.tools.bossac.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\bossac\1.7.0-arduino3 -prefs=runtime.tools.bossac-1.7.0-arduino3.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\bossac\1.7.0-arduino3 -verbose C:\Program Files (x86)\Arduino\examples\01.Basics\Blink\Blink.ino
C:\Program Files (x86)\Arduino\arduino-builder -compile -logger=machine -hardware C:\Program Files (x86)\Arduino\hardware -hardware C:\Users\mattr\AppData\Local\Arduino15\packages -tools C:\Program Files (x86)\Arduino\tools-builder -tools C:\Program Files (x86)\Arduino\hardware\tools\avr -tools C:\Users\mattr\AppData\Local\Arduino15\packages -built-in-libraries C:\Program Files (x86)\Arduino\libraries -libraries C:\Users\mattr\OneDrive\Documents\Arduino\libraries -fqbn=arduino:samd:mkrnb1500 -vid-pid=2341_8055 -ide-version=10815 -build-path C:\Users\mattr\AppData\Local\Temp\arduino_build_126111 -warnings=none -build-cache C:\Users\mattr\AppData\Local\Temp\arduino_cache_16133 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.arduinoOTA.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\arduinoOTA\1.2.1 -prefs=runtime.tools.arduinoOTA-1.2.1.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\arduinoOTA\1.2.1 -prefs=runtime.tools.CMSIS-Atmel.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\CMSIS-Atmel\1.2.0 -prefs=runtime.tools.CMSIS-Atmel-1.2.0.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\CMSIS-Atmel\1.2.0 -prefs=runtime.tools.arm-none-eabi-gcc.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\arm-none-eabi-gcc\7-2017q4 -prefs=runtime.tools.arm-none-eabi-gcc-7-2017q4.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\arm-none-eabi-gcc\7-2017q4 -prefs=runtime.tools.CMSIS.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\CMSIS\4.5.0 -prefs=runtime.tools.CMSIS-4.5.0.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\CMSIS\4.5.0 -prefs=runtime.tools.openocd.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\openocd\0.10.0-arduino7 -prefs=runtime.tools.openocd-0.10.0-arduino7.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\openocd\0.10.0-arduino7 -prefs=runtime.tools.bossac.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\bossac\1.7.0-arduino3 -prefs=runtime.tools.bossac-1.7.0-arduino3.path=C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\bossac\1.7.0-arduino3 -verbose C:\Program Files (x86)\Arduino\examples\01.Basics\Blink\Blink.ino
Using board 'mkrnb1500' from platform in folder: C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\hardware\samd\1.8.11
Using core 'arduino' from platform in folder: C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\hardware\samd\1.8.11
Detecting libraries used...
"C:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\arm-none-eabi-gcc\\7-2017q4/bin/arm-none-eabi-g++" -mcpu=cortex-m0plus -mthumb -c -g -Os -w -std=gnu++11 -ffunction-sections -fdata-sections -fno-threadsafe-statics -nostdlib --param max-inline-insns-single=500 -fno-rtti -fno-exceptions -w -x c++ -E -CC -DF_CPU=48000000L -DARDUINO=10815 -DARDUINO_SAMD_MKRNB1500 -DARDUINO_ARCH_SAMD -DUSE_ARDUINO_MKR_PIN_LAYOUT -D__SAMD21G18A__ -DUSB_VID=0x2341 -DUSB_PID=0x8055 -DUSBCON "-DUSB_MANUFACTURER=\"Arduino LLC\"" "-DUSB_PRODUCT=\"Arduino MKR NB 1500\"" -DUSE_BQ24195L_PMIC "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\CMSIS\\4.5.0/CMSIS/Include/" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\CMSIS-Atmel\\1.2.0/CMSIS/Device/ATMEL/" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino/api/deprecated" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino/api/deprecated-avr-comp" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\variants\\mkrnb1500" "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111\\sketch\\Blink.ino.cpp" -o nul
Generating function prototypes...
"C:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\arm-none-eabi-gcc\\7-2017q4/bin/arm-none-eabi-g++" -mcpu=cortex-m0plus -mthumb -c -g -Os -w -std=gnu++11 -ffunction-sections -fdata-sections -fno-threadsafe-statics -nostdlib --param max-inline-insns-single=500 -fno-rtti -fno-exceptions -w -x c++ -E -CC -DF_CPU=48000000L -DARDUINO=10815 -DARDUINO_SAMD_MKRNB1500 -DARDUINO_ARCH_SAMD -DUSE_ARDUINO_MKR_PIN_LAYOUT -D__SAMD21G18A__ -DUSB_VID=0x2341 -DUSB_PID=0x8055 -DUSBCON "-DUSB_MANUFACTURER=\"Arduino LLC\"" "-DUSB_PRODUCT=\"Arduino MKR NB 1500\"" -DUSE_BQ24195L_PMIC "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\CMSIS\\4.5.0/CMSIS/Include/" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\CMSIS-Atmel\\1.2.0/CMSIS/Device/ATMEL/" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino/api/deprecated" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino/api/deprecated-avr-comp" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\variants\\mkrnb1500" "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111\\sketch\\Blink.ino.cpp" -o "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111\\preproc\\ctags_target_for_gcc_minus_e.cpp"
"C:\\Program Files (x86)\\Arduino\\tools-builder\\ctags\\5.8-arduino11/ctags" -u --language-force=c++ -f - --c++-kinds=svpf --fields=KSTtzns --line-directives "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111\\preproc\\ctags_target_for_gcc_minus_e.cpp"
Compiling sketch...
"C:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\arm-none-eabi-gcc\\7-2017q4/bin/arm-none-eabi-g++" -mcpu=cortex-m0plus -mthumb -c -g -Os -w -std=gnu++11 -ffunction-sections -fdata-sections -fno-threadsafe-statics -nostdlib --param max-inline-insns-single=500 -fno-rtti -fno-exceptions -MMD -DF_CPU=48000000L -DARDUINO=10815 -DARDUINO_SAMD_MKRNB1500 -DARDUINO_ARCH_SAMD -DUSE_ARDUINO_MKR_PIN_LAYOUT -D__SAMD21G18A__ -DUSB_VID=0x2341 -DUSB_PID=0x8055 -DUSBCON "-DUSB_MANUFACTURER=\"Arduino LLC\"" "-DUSB_PRODUCT=\"Arduino MKR NB 1500\"" -DUSE_BQ24195L_PMIC "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\CMSIS\\4.5.0/CMSIS/Include/" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\CMSIS-Atmel\\1.2.0/CMSIS/Device/ATMEL/" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino/api/deprecated" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino/api/deprecated-avr-comp" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\variants\\mkrnb1500" "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111\\sketch\\Blink.ino.cpp" -o "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111\\sketch\\Blink.ino.cpp.o"
Compiling libraries...
Compiling core...
"C:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\arm-none-eabi-gcc\\7-2017q4/bin/arm-none-eabi-g++" -mcpu=cortex-m0plus -mthumb -c -g -Os -w -std=gnu++11 -ffunction-sections -fdata-sections -fno-threadsafe-statics -nostdlib --param max-inline-insns-single=500 -fno-rtti -fno-exceptions -MMD -DF_CPU=48000000L -DARDUINO=10815 -DARDUINO_SAMD_MKRNB1500 -DARDUINO_ARCH_SAMD -DUSE_ARDUINO_MKR_PIN_LAYOUT -D__SAMD21G18A__ -DUSB_VID=0x2341 -DUSB_PID=0x8055 -DUSBCON "-DUSB_MANUFACTURER=\"Arduino LLC\"" "-DUSB_PRODUCT=\"Arduino MKR NB 1500\"" -DUSE_BQ24195L_PMIC "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\CMSIS\\4.5.0/CMSIS/Include/" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\CMSIS-Atmel\\1.2.0/CMSIS/Device/ATMEL/" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino/api/deprecated" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino/api/deprecated-avr-comp" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\cores\\arduino" "-IC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\variants\\mkrnb1500" "C:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\variants\\mkrnb1500\\variant.cpp" -o "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111\\core\\variant.cpp.o"
Using precompiled core: C:\Users\mattr\AppData\Local\Temp\arduino_cache_16133\core\core_arduino_samd_mkrnb1500_b54adf36dfefcfd47b0f5f53e70f6d2d.a
Linking everything together...
"C:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\arm-none-eabi-gcc\\7-2017q4/bin/arm-none-eabi-g++" "-LC:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111" -Os -Wl,--gc-sections -save-temps "-TC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\samd\\1.8.11\\variants\\mkrnb1500/linker_scripts/gcc/flash_with_bootloader.ld" "-Wl,-Map,C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111/Blink.ino.map" --specs=nano.specs --specs=nosys.specs -mcpu=cortex-m0plus -mthumb -Wl,--cref -Wl,--check-sections -Wl,--gc-sections -Wl,--unresolved-symbols=report-all -Wl,--warn-common -Wl,--warn-section-align -o "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111/Blink.ino.elf" "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111\\sketch\\Blink.ino.cpp.o" "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111\\core\\variant.cpp.o" -Wl,--start-group "-LC:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\CMSIS\\4.5.0/CMSIS/Lib/GCC/" -larm_cortexM0l_math -lm "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111/..\\arduino_cache_16133\\core\\core_arduino_samd_mkrnb1500_b54adf36dfefcfd47b0f5f53e70f6d2d.a" -Wl,--end-group
"C:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\arm-none-eabi-gcc\\7-2017q4/bin/arm-none-eabi-objcopy" -O binary "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111/Blink.ino.elf" "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111/Blink.ino.bin"
"C:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\arm-none-eabi-gcc\\7-2017q4/bin/arm-none-eabi-objcopy" -O ihex -R .eeprom "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111/Blink.ino.elf" "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111/Blink.ino.hex"
"C:\\Users\\mattr\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\arm-none-eabi-gcc\\7-2017q4/bin/arm-none-eabi-size" -A "C:\\Users\\mattr\\AppData\\Local\\Temp\\arduino_build_126111/Blink.ino.elf"
Sketch uses 12012 bytes (4%) of program storage space. Maximum is 262144 bytes.
Global variables use 2204 bytes (6%) of dynamic memory, leaving 30564 bytes for local variables. Maximum is 32768 bytes.
Forcing reset using 1200bps open/close on port COM3
PORTS {COM1, COM3, } / {COM1, COM3, } => {}
PORTS {COM1, COM3, } / {COM1, COM3, COM4, } => {COM4, }
Found upload port: COM4
C:\Users\mattr\AppData\Local\Arduino15\packages\arduino\tools\bossac\1.7.0-arduino3/bossac.exe -i -d --port=COM4 -U true -i -e -w -v C:\Users\mattr\AppData\Local\Temp\arduino_build_126111/Blink.ino.bin -R 
Set binary mode
readWord(addr=0)=0x20007ffc
readWord(addr=0xe000ed00)=0x410cc601
readWord(addr=0x41002018)=0x10010305
version()=v2.0 [Arduino:XYZ] Mar 26 2018 12:29:38
chipId=0x10010005
Connected at 921600 baud
readWord(addr=0)=0x20007ffc
readWord(addr=0xe000ed00)=0x410cc601
readWord(addr=0x41002018)=0x10010305
Atmel SMART device 0x10010005 found
write(addr=0x20004000,size=0x34)
writeWord(addr=0x20004030,value=0x10)
writeWord(addr=0x20004020,value=0x20008000)
Device       : ATSAMD21G18A
readWord(addr=0)=0x20007ffc
readWord(addr=0xe000ed00)=0x410cc601
readWord(addr=0x41002018)=0x10010305
Chip ID      : 10010005
version()=v2.0 [Arduino:XYZ] Mar 26 2018 12:29:38
Version      : v2.0 [Arduino:XYZ] Mar 26 2018 12:29:38
Address      : 8192
Pages        : 3968
Page Size    : 64 bytes
Total Size   : 248KB
Planes       : 1
Lock Regions : 16
Locked       : readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
readWord(addr=0x41004020)=0xffff
none
readWord(addr=0x41004018)=0
Security     : false
Boot Flash   : true
readWord(addr=0x40000834)=0x7000a
BOD          : true
readWord(addr=0x40000834)=0x7000a
BOR          : true
Arduino      : FAST_CHIP_ERASE
Arduino      : FAST_MULTI_PAGE_WRITE
Arduino      : CAN_CHECKSUM_MEMORY_BUFFER
Erase flash
chipErase(addr=0x2000)
done in 0.796 seconds

Write 12012 bytes to flash (188 pages)
write(addr=0x20005000,size=0x1000)
writeBuffer(scr_addr=0x20005000, dst_addr=0x2000, size=0x1000)
[==========                    ] 34% (64/188 pages)write(addr=0x20005000,size=0x1000)
writeBuffer(scr_addr=0x20005000, dst_addr=0x3000, size=0x1000)
[====================          ] 68% (128/188 pages)write(addr=0x20005000,size=0xf00)
writeBuffer(scr_addr=0x20005000, dst_addr=0x4000, size=0xf00)
[==============================] 100% (188/188 pages)
done in 0.089 seconds

Verify 12012 bytes of flash with checksum.
checksumBuffer(start_addr=0x2000, size=0x1000) = 4030
checksumBuffer(start_addr=0x3000, size=0x1000) = 8d76
checksumBuffer(start_addr=0x4000, size=0xeec) = 8927
Verify successful
done in 0.011 seconds
CPU reset.
readWord(addr=0)=0x20007ffc
readWord(addr=0xe000ed00)=0x410cc601
readWord(addr=0x41002018)=0x10010305
writeWord(addr=0xe000ed0c,value=0x5fa0004)

sterretje · July 12, 2021, 4:43am

@greenboba, your topic has been moved to a more suitable location on the forum.

I'm not familiar with the board but this is intended behaviour of boards with native USB. The IDE forces a reset of the board to activate the boot loader; see your output Forcing reset using 1200bps open/close on port COM3.

Do you experience problems?

greenboba · July 12, 2021, 1:35pm

Thank you for moving the topic to a better place and for your response.

Yes I think it is a problem because this doesn’t happen with my other board MKR1000, but maybe I’m doing something wrong with the MKR1500?

Let’s say I run a simple sketch with the loop being:

void loop() 
{
Serial.println(“Hello World”);
delay(1000);
}

If I upload this sketch, I’ll see Hello World appear around 4 to 5 times in the Serial Monitor for COM3, then I hear a disconnect sound and suddenly the board is in bootloader mode on COM4. I’m guessing this is why the Serial Monitor stops printing Hello World on COM3.

At this point, with the upload still “running” on COM3, if I switch to COM4 and open the Serial Monitor nothing is printing and it is empty.

With my other board, the MKR1000, the only time it enters bootloader mode seems to be when I double-tap the reset button. I’d expect similar behaviour from the MKR1500, but it seems to just enter bootloader mode by itself.

greenboba · July 17, 2021, 9:14pm

I managed to get rid of this problem, here's what I did:

With the board plugged in, double-tap the on-board RESET button to force bootloader mode.
Immediately unplug the USB cable.
Hold down the on-board RESET button, don't let go yet.
Plug the USB cable back into your PC, but this time in a different port. (You can try using a different USB cable too).
Release the RESET button.

And that's it, upload a simple Arduino sketch just to be sure everything works. I'm not sure what these steps actually do, but I have a feeling my old Arduino board (which stopped working) damaged a USB port on my PC and maybe even the USB cable too.

Even if this seems like a very specific problem, I hope this can help someone.

sterretje · July 19, 2021, 4:53pm

I don't have the board and I'm not familiar with the board.

But thanks for the feedback. Let's hope somebody more familiar can shine a light on it.

system · November 16, 2021, 4:54pm

This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.

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COM Port Disconnects and Always Goes Into Bootloader Mode

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