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.
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 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 filename0 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,
MOUSEKEY_ENABLE, EXTRAKEY_ENABLE, CONSOLE_ENABLE, API_SYSEX_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
EEPROM has around a 100000 (100k) write cycle. You shouldn't rewrite
the firmware repeatedly and continually; that'll burn the EEPROM
First you have to compile firmware with the build option
NKRO_ENABLE in Makefile.
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.
If your firmware was 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.
Without reset circuit you will have inconsistent result due to improper initialization of the hardware. See circuit schematic of TPM754:
1UL<<16 instead of
read_cols() in [matrix.h] when your columns goes beyond 16.
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
You need to define
rules.mk to use them in QMK.
EXTRAKEY_ENABLE = yes # Audio control and System control
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.
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.
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
Some problems can be fixed by switching from a USB 3.x port to a USB 2.0 port.
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
SLEEP_LED_ENABLE and/or others.