I bought this Pro Micro on eBay a while back, and I never really got around to using it. But now that I do my iMac won't recognize the board. I plug it into my iMac and open Arduino and go to the board tab, and it doesn't even have a Pro Micro choice, so I just choose Micro.

In ports it isn't showing up like my other boards do. Is it my computer, because my Chinese clone Uno and Mega weren't being recognized a while ago? I downloaded the CH340 chip driver for them because they used the CH340 chip and now they are recognized and work perfectly!

The thing is the Pro Micro does not use that chip so is there something else I have to do like another driver to download? It is not the cable because I have tried 5 cables and some had the symbol with the circle triangle and square connected on them, which is the usb serial symbol I think, so they aren't just power cables. If anyone knows what the problem is, that would be awesome! Here is the error it gives me when I try to upload it.

 Arduino: 1.6.9 (Mac OS X), Board: "Arduino/Genuino Micro"

failed MSpanList_Insert 0x31dea0 0x29ab70fa1fa 0x0
fatal error: MSpanList_Insert

runtime stack:
runtime.MSpanList_Insert(0x2c70d0, 0x31dea0)
/usr/local/go/src/runtime/mheap.c:692 +0x8f
runtime.MHeap_Alloc(0x2c6d20, 0x6, 0x10000000034, 0xf989)
runtime.MCentral_CacheSpan(0x2d10d8, 0x30c270)
/usr/local/go/src/runtime/mcentral.c:85 +0x167
runtime.MCache_Refill(0x308000, 0xc200000034, 0x30c270)
/usr/local/go/src/runtime/mcache.c:90 +0xa0

 goroutine 1 [running]:
/usr/local/go/src/runtime/asm_amd64.s:198 fp=0xc2082b7468          sp=0xc2082b7460
 runtime.mallocgc(0x2200, 0x19ff80, 0x0, 0xc2080d68e9)
/usr/local/go/src/runtime/malloc.go:178 +0x849 fp=0xc2082b7518     sp=0xc2082b7468
 runtime.newarray(0x19ff80, 0x20, 0xa5ca)
/usr/local/go/src/runtime/malloc.go:365 +0xc1 fp=0xc2082b7550    sp=0xc2082b7518
 runtime.hashGrow(0x1b4300, 0xc2080dc150)
/usr/local/go/src/runtime/hashmap.go:744 +0x86 fp=0xc2082b7580    sp=0xc2082b7550
 runtime.mapassign1(0x1b4300, 0xc2080dc150, 0xc2082b7698, 0xc2082b7688)
/usr/local/go/src/runtime/hashmap.go:456 +0x568 fp=0xc2082b7620  sp=0xc2082b7580
  arduino.cc/builder/props.PropertiesMap.Merge(0xc2080dc150,      0xc2082b7748, 0x1, 0x1, 0x3)
/Users/jenkins/jenkins/workspace/arduino-builder-     macosx/src/arduino.cc/builder/props/properties.go:162 +0x153     fp=0xc2082b7718 sp=0xc2082b7620
 arduino.cc/builder/props.PropertiesMap.Clone(0xc20803ce40, 0xb2f5f)
/Users/jenkins/jenkins/workspace/arduino-builder-    macosx/src/arduino.cc/builder/props/properties.go:170 +0xad fp=0xc2082b7770     sp=0xc2082b7718
 arduino.cc/builder.(*RecipeByPrefixSuffixRunner).Run(0xc20801e300,     0xc208068000, 0x0, 0x0)
/Users/jenkins/jenkins/workspace/arduino-builder-    macosx/src/arduino.cc/builder/recipe_runner.go:53 +0x2c4 fp=0xc2082b78e8    sp=0xc2082b7770
arduino.cc/builder.runCommands(0xc208068000, 0xc2082b7af8, 0x1c, 0x1c,     0xc208038001, 0x0, 0x0)
/Users/jenkins/jenkins/workspace/arduino-builder-   macosx/src/arduino.cc/builder/builder.go:181 +0x139 fp=0xc2082b7978    sp=0xc2082b78e8
 arduino.cc/builder.(*Builder).Run(0xc2082b7ce0, 0xc208068000, 0x0,   0x0)
/Users/jenkins/jenkins/workspace/arduino-builder-  macosx/src/arduino.cc/builder/builder.go:116 +0xe8e fp=0xc2082b7cc0   sp=0xc2082b7978
 arduino.cc/builder.RunBuilder(0xc208068000, 0x0, 0x0)
/Users/jenkins/jenkins/workspace/arduino-builder- macosx/src/arduino.cc/builder/builder.go:212 +0x49 fp=0xc2082b7ce8  sp=0xc2082b7cc0
/Users/jenkins/jenkins/workspace/arduino-builder-   macosx/src/arduino.cc/arduino-builder/main.go:316 +0x171b fp=0xc2082b7f98    sp=0xc2082b7ce8
/usr/local/go/src/runtime/proc.go:63 +0xf3 fp=0xc2082b7fe0   sp=0xc2082b7f98
/usr/local/go/src/runtime/asm_amd64.s:2232 +0x1 fp=0xc2082b7fe8    sp=0xc2082b7fe0
arduino-builder returned 2
Error compiling for board Arduino/Genuino Micro.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.
  • Click the apple logo in the top left corner ; click About This Mac; click More Info…; click System Report…; then under Hardware click USB and see if anything gets added when you plug in the Arduino. Let us know if or if not. It could be a bare board without bootloader.
    – Gerben
    Feb 11, 2017 at 19:51
  • No nothing shows up what do i do? Feb 11, 2017 at 20:04
  • Try and upload the bootloader to the Arduino. You might need to use a second Arduino to do this.
    – Gerben
    Feb 11, 2017 at 20:19
  • Ok how do i do that? Feb 11, 2017 at 20:27
  • 2
    Your error appears to be with compilation not uploading. To make sure, try the verify button rather than the upload one. If it still fails, the problem is the sketch and/or Arduino install, not the board or USB. Feb 11, 2017 at 20:46

1 Answer 1


From what you say here:

I plug it into my iMac and open Arduino and go to the board tab, and it doesn't even have a Pro Micro choice, so i just choose Micro.

and from the dump you provide:

Arduino: 1.6.9 (Mac OS X), Board: "Arduino/Genuino Micro"

It looks to me like you're selecting the wrong board. Instead of just picking a "similar" board from the Tools menu, what you should do is add the Sparkfun board manager package and then select the Pro Micro from it.

Here you can find the procedure step by step. Follow it and you should be all set.


If you tried to upload a sketch with a wrong board selection, then your your Pro Micro may have become "bricked". In order to unbrick it, follow this procedure (same link as above, different section).

Once you unbrick it, upload the specific blink example code for Pro Micro that you can find in another section of the same link.

If it keeps not working, READ THE ENTIRE ARTICLE linked and try out all troubleshooting instructions before anything else.

  • Let us know whether it worked or not. :) Feb 13, 2017 at 15:41
  • Ok i downloaded the sparkfun thing and choose the correct board, and I downloaded the boot loader to it using an Uno and it still doesn't show up in my serial port tab!! Feb 14, 2017 at 2:24
  • no port is even coming in not only is it not working it isn't existent!! Feb 14, 2017 at 2:26
  • Please help me :( Feb 14, 2017 at 2:27
  • If its any help i downloaded the boot loader to the pro micro and the two red lights that were on it turned off and only a green light is present now, what does that mean?? Feb 14, 2017 at 2:30

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