# Frequently Asked Build Questions This page covers questions about building QMK. If you haven't yet done so, you should read the [Build Environment Setup](getting_started_build_tools.md) and [Make Instructions](getting_started_make_guide.md) guides. ## Can't Program on Linux You will need proper permissions to operate a device. For Linux users, see the instructions regarding `udev` rules, below. If you have issues with `udev`, a work-around is to use the `sudo` command. If you are not familiar with this command, check its manual with `man sudo` or [see this webpage](https://linux.die.net/man/8/sudo). An example of using `sudo`, 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 Note that running `make` with `sudo` is generally *not* a good idea, and you should use one of the former methods, if possible. ## Linux `udev` Rules On Linux, you'll need proper privileges to access the MCU. You can either use `sudo` when flashing firmware, or place these files in `/etc/udev/rules.d/`. **/etc/udev/rules.d/50-atmel-dfu.rules:** ``` # 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" ``` **/etc/udev/rules.d/52-tmk-keyboard.rules:** ``` # tmk keyboard products https://github.com/tmk/tmk_keyboard SUBSYSTEMS=="usb", ATTRS{idVendor}=="feed", MODE:="0666" ``` ## WINAVR is Obsolete It is no longer recommended and may cause some problem. See [TMK Issue #99](https://github.com/tmk/tmk_keyboard/issues/99). ## USB VID and PID 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. https://github.com/tmk/tmk_keyboard/issues/150 You can buy a really unique VID:PID here. I don't think you need this for personal use. - http://www.obdev.at/products/vusb/license.html - http://www.mcselec.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=92&option=com_phpshop&Itemid=1 ## 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. https://launchpad.net/~terry.guo/+archive/ubuntu/gcc-arm-embedded https://github.com/tmk/tmk_keyboard/issues/212 https://github.com/tmk/tmk_keyboard/wiki/mbed-cortex-porting#compile-error-cstddef https://developer.mbed.org/forum/mbed/topic/5205/ ## `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 ``` ## BOOTLOADER_SIZE for AVR 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 OPT_DEFS += -DBOOTLOADER_SIZE=2048 ``` ## `avr-gcc: internal compiler error: Abort trap: 6 (program cc1)` on MacOS This is an issue with updating on brew, causing symlinks that avr-gcc depend on getting mangled. The solution is to remove and reinstall all affected modules. ``` brew rm avr-gcc brew rm dfu-programmer brew rm gcc-arm-none-eabi brew rm avrdude brew install avr-gcc brew install dfu-programmer brew install gcc-arm-none-eabi brew install avrdude ``` ### avr-gcc 8.1 and LUFA If you updated your avr-gcc to above 7 you may see errors involving LUFA. For example: `lib/lufa/LUFA/Drivers/USB/Class/Device/AudioClassDevice.h:380:5: error: 'const' attribute on function returning 'void'` For now, you need to rollback avr-gcc to 7 in brew. ``` brew uninstall --force avr-gcc brew install avr-gcc@7 brew link avr-gcc@7 ```