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Miscellaneous FAQ

How do I test my keyboard?

Testing your keyboard is usually pretty straightforward. Press every single key and make sure it sends the keys you expect. You can use QMK Configurator's test mode to check your keyboard, even if it doesn't run QMK.

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 QK_BOOT, 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 inoperable
  • 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 e.g. 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 28672/7000h
  • 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, MOUSEKEY_ENABLE, EXTRAKEY_ENABLE, CONSOLE_ENABLE
  • DFU tools do /not/ allow you to write into the bootloader (unless you throw in an extra fruit salad of options), so there is little risk there.
  • EEPROM has around a 100000 (100k) write cycle. You shouldn't rewrite the firmware repeatedly and continually; that'll burn the EEPROM eventually.

NKRO Doesn't work

First you have to compile firmware with the 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 and you will need to switch to 6KRO mode, in particular when you are in BIOS.

TrackPoint Needs Reset Circuit (PS/2 Mouse Support)

Without reset circuit you will have inconsistent result due to improper initialization 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. Thus, calculating 1<<16 will unexpectedly equal zero. To work around this, 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

Wake 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 your BIOS settings. 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

Some problems can be fixed by switching from a USB 3.x port to a USB 2.0 port.

Mac Compatibility

OS X 10.11 and Hub

See here:

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

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

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

More info: