Debugging/Troubleshooting QMK

Debugging FAQ

This page details various common questions people have about troubleshooting their keyboards.

Debug Console

hid_listen Can't Recognize Device

When debug console of your device is not ready you will see like this:

Waiting for device:.........

once the device is plugged in then hid_listen finds it you will get this message:

Waiting for new device:.........................

If you can't get this 'Listening:' message try building with CONSOLE_ENABLE=yes in [Makefile]

You may need privilege to access the device on OS like Linux.

  • try sudo hid_listen

Can't Get Message on Console


  • hid_listen finds your device. See above.

  • Enable debug with pressing Magic+d. See Magic Commands.

  • set debug_enable=true. See Testing and Debugging

  • try using 'print' function instead of debug print. See common/print.h.

  • disconnect other devices with console function. See Issue #97.


Safety Considerations

You probably don't want to "brick" your keyboard, making it impossible to rewrite firmware onto it. Here are some of the parameters to show what things are (and likely aren't) too risky.

  • If your keyboard map does not include RESET, then, to get into DFU

    mode, you will need to press the reset button on the PCB, which

    requires unscrewing the bottom.

  • Messing with tmk_core / common files might make the keyboard


  • Too large a .hex file is trouble; make dfu will erase the block,

    test the size (oops, wrong order!), which errors out, failing to

    flash the keyboard, leaving it in DFU mode.

    • To this end, note that the maximum .hex file size on Planck is

      7000h (28672 decimal)

Linking: .build/planck_rev4_cbbrowne.elf [OK]
Creating load file for Flash: .build/planck_rev4_cbbrowne.hex [OK]
Size after:
text data bss dec hex filename
0 22396 0 22396 577c planck_rev4_cbbrowne.hex
  • The above file is of size 22396/577ch, which is less than


  • As long as you have a suitable alternative .hex file around, you

    can retry, loading that one

  • Some of the options you might specify in your keyboard's Makefile

    consume extra memory; watch out for BOOTMAGIC_ENABLE,


    • DFU tools do /not/ allow you to write into the bootloader (unless

      you throw in extra fruit salad of options), so there is little risk


    • EEPROM has around a 100000 write cycle. You shouldn't rewrite the

      firmware repeatedly and continually; that'll burn the EEPROM


NKRO Doesn't work

First you have to compile firmware with this build option NKRO_ENABLE in Makefile.

Try Magic N command(LShift+RShift+N by default) when NKRO still doesn't work. You can use this command to toggle between NKRO and 6KRO mode temporarily. In some situations NKRO doesn't work you need to switch to 6KRO mode, in particular when you are in BIOS.

If your firmware built with BOOTMAGIC_ENABLE you need to turn its switch on by BootMagic N command(Space+N by default). This setting is stored in EEPROM and kept over power cycles.

TrackPoint Needs Reset Circuit (PS/2 Mouse Support)

Without reset circuit you will have inconsistent result due to improper initialize of the hardware. See circuit schematic of TPM754.

Can't Read Column of Matrix Beyond 16

Use 1UL<<16 instead of 1<<16 in read_cols() in [matrix.h] when your columns goes beyond 16.

In C 1 means one of [int] type which is [16 bit] in case of AVR so you can't shift left more than 15. You will get unexpected zero when you say 1<<16. You have to use [unsigned long] type with 1UL.

Special Extra Key Doesn't Work (System, Audio Control Keys)

You need to define EXTRAKEY_ENABLE in to use them in QMK.

EXTRAKEY_ENABLE = yes # Audio control and System control

Wakeup from Sleep Doesn't Work

In Windows check Allow this device to wake the computer setting in Power Management property tab of Device Manager. Also check BIOS setting.

Pressing any key during sleep should wake host.

Using Arduino?

Note that Arduino pin naming is different from actual chip. For example, Arduino pin D0 is not PD0. Check circuit with its schematics yourself.

Arduino Leonardo and micro have ATMega32U4 and can be used for TMK, though Arduino bootloader may be a problem.

Enabling JTAG

By default, the JTAG debugging interface is disabled as soon as the keyboard starts up. JTAG-capable MCUs come from the factory with the JTAGEN fuse set, and it takes over certain pins of the MCU that the board may be using for the switch matrix, LEDs, etc.

If you would like to keep JTAG enabled, just add the following to your config.h:


USB 3 Compatibility

I heard some people have a problem with USB 3 port, try USB 2 port.

Mac Compatibility

OS X 10.11 and Hub

Problem on BIOS (UEFI)/Resume (Sleep & Wake)/Power Cycles

Some people reported their keyboard stops working on BIOS and/or after resume(power cycles).

As of now root of its cause is not clear but some build options seem to be related. In Makefile try to disable those options like CONSOLE_ENABLE, NKRO_ENABLE, SLEEP_LED_ENABLE and/or others.