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