Frequently Asked Build Questions

This page covers questions about building QMK. If you have not yet you should read the Build Environment Setup and Make Instructions guides.

Can't program on Linux

You will need proper permission to operate a device. For Linux users see udev rules below. Easy way is to use sudo command, if you are not familiar with this command check its manual with man sudo or this page on line.

In short when your controller is ATMega32u4,

$ sudo dfu-programmer atmega32u4 erase --force
$ sudo dfu-programmer atmega32u4 flash your.hex
$ sudo dfu-programmer atmega32u4 reset

or just

$ sudo make <keyboard>-<keymap>-dfu

But to run make with root privilege is not good idea. Use former method if possible.

WINAVR is obsolete

It is no longer recommended and may cause some problem. See TMK Issue #99.


You can use any ID you want with editing config.h. Using any presumably unused ID will be no problem in fact except for very low chance of collision with other product.

Most boards in QMK use 0xFEED as the vendor ID. You should look through other keyboards to make sure you pick a unique Product ID.

Also see this.

You can buy a really unique VID:PID here. I don't think you need this for personal use.

Linux udev rules

On Linux you need proper privilege to access device file of MCU, you'll have to use sudo when flashing firmware. You can circumvent this with placing these files in /etc/udev/rules.d/.


# Atmel ATMega32U4
SUBSYSTEMS=="usb", ATTRS{idVendor}=="03eb", ATTRS{idProduct}=="2ff4", MODE:="0666"
# Atmel USBKEY AT90USB1287
SUBSYSTEMS=="usb", ATTRS{idVendor}=="03eb", ATTRS{idProduct}=="2ffb", MODE:="0666"
# Atmel ATMega32U2
SUBSYSTEMS=="usb", ATTRS{idVendor}=="03eb", ATTRS{idProduct}=="2ff0", MODE:="0666"


# tmk keyboard products
SUBSYSTEMS=="usb", ATTRS{idVendor}=="feed", MODE:="0666"

Cortex: cstddef: No such file or directory

GCC 4.8 of Ubuntu 14.04 had this problem and had to update to 4.9 with this PPA.

'clock_prescale_set' and 'clock_div_1' not available

Your toolchain is too old to support the MCU. For example WinAVR 20100110 doesn't support ATMega32u2.

Compiling C: ../../tmk_core/protocol/lufa/lufa.c
avr-gcc -c -mmcu=atmega32u2 -gdwarf-2 -DF_CPU=16000000UL -DINTERRUPT_CONTROL_ENDPOINT -DBOOTLOADER_SIZE=4096 -DF_USB=16000000UL -DARCH=ARCH_AVR8 -DUSB_DEVICE_ONLY -DUSE_FLASH_DESCRIPTORS -DUSE_STATIC_OPTIONS="(USB_DEVICE_OPT_FULLSPEED | USB_OPT_REG_ENABLED | USB_OPT_AUTO_PLL)" -DFIXED_CONTROL_ENDPOINT_SIZE=8  -DFIXED_NUM_CONFIGURATIONS=1 -DPROTOCOL_LUFA -DEXTRAKEY_ENABLE -DCONSOLE_ENABLE -DCOMMAND_ENABLE -DVERSION=unknown -Os -funsigned-char -funsigned-bitfields -ffunction-sections -fdata-sections -fno-inline-small-functions -fpack-struct -fshort-enums -fno-strict-aliasing -Wall -Wstrict-prototypes -Wa,-adhlns=obj_alps64/protocol/lufa/lufa.lst -I. -I../../tmk_core -I../../tmk_core/protocol/lufa -I../../tmk_core/protocol/lufa/LUFA-git -I../../tmk_core/common -std=gnu99 -include config.h -MMD -MP -MF .dep/obj_alps64_protocol_lufa_lufa.o.d  ../../tmk_core/protocol/lufa/lufa.c -o obj_alps64/protocol/lufa/lufa.o
../../tmk_core/protocol/lufa/lufa.c: In function 'setup_mcu':
../../tmk_core/protocol/lufa/lufa.c:575: warning: implicit declaration of function 'clock_prescale_set'
../../tmk_core/protocol/lufa/lufa.c:575: error: 'clock_div_1' undeclared (first use in this function)
../../tmk_core/protocol/lufa/lufa.c:575: error: (Each undeclared identifier is reported only once
../../tmk_core/protocol/lufa/lufa.c:575: error: for each function it appears in.)
make: *** [obj_alps64/protocol/lufa/lufa.o] Error 1


Note that Teensy2.0++ bootloader size is 2048byte. Some Makefiles may have wrong comment.

# Boot Section Size in *bytes*    
#   Teensy halfKay   512          
#   Teensy++ halfKay 2048         
#   Atmel DFU loader 4096       (TMK Alt Controller)
#   LUFA bootloader  4096         
#   USBaspLoader     2048         

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