====== Get the firmware ======

You can either take a pre-built firmware package from [[http://www.smarthomatic.org/builds/builds.html]] or [[build your own firmware|build your own firmware]]. If you take the prebuilt package, extract it to a directory of your choice.

====== Three different storage areas ======

Every microcontroller has three parts that can be flashed (written):

  * Three **fuse bytes** contains microcontroller specific configuration bits. These should only be set once.
  * The **flash memory** contains the firmware. It can be overwritten about 10.000 times.
  * The **EEPROM memory** contains (firmware) configuration data. It is also written to by the device in normal operation. It can we overwritten about 100.000 times.

{{danger.gif}} **In general, it's a good idea to only flash what you need to, because of the limited amount of possible write cycles.**

====== Programming fuses ======

===== Using a make rule =====

If you build your binaries by yourself with "make", your fuse settings should be available as files **lfuse.bin**, **hfuse.bin** and **efuse.bin** in the bin subdirectory **of the device you want to flash**. You can write these fuses with:

<code>
make program_fuses
</code>

Be sure about the fuse settings you want to write in your microcontroller. With wrong fuse settings, your microcontroller might not be accessible anymore!

===== Calling avrdude directly =====

If you are creating a new or modified SHC device, you may want to write other than the default fuses. You can do so with:

<code>
avrdude -p ATMEGA328P -U lfuse:w:0x??:m
</code>

(replace ?? by the hex value for the needed fuse settings and use "lfuse", "hfuse" or "efuse" accordingly).

===== Strange avrdude error messages =====

Some fuses only use a part of their bits. If you set such a fuse, avrdude may complain at verification that it read out another value than it wrote.

Writing the EFuse of the ATMega168 or 328 returns a value of only the last 3 bits (upper 5 unused), so a value of xxxxxyyy is read out as 00000yyy. Example:

<code>
avrdude: verification error, first mismatch at byte 0x0000
         0xfc != 0x04
avrdude: verification error; content mismatch
</code>

Don't worry. The warning is only returned because avrdude does not know that the upper 5 bits are always 1 (as per spec).

====== Flashing the firmware / eeprom ======

===== Using flash scripts =====

After setting up avrdude, you can flash the firmware by calling the flash scripts

  * **flash.cmd** / **flash.sh** for flashing firmware, eeprom and fuses
  * **flash_firmware.cmd** / **flash_firmware.sh** for flashing only the firmware

===== Using a make rule =====

If you have the source code on your machine, you can flash the firmware with the following command from the firmware subdirectory:

<code>
make program
</code>

===== Calling avrdude directly =====

If you want to call avrdude by hand you can flash everything with:

<code>
avrdude -p m328p -U flash:w:shc_basestation.hex -U eeprom:w:shc_basestation.e2p:r -U lfuse:w:lfuse.bin:r -U hfuse:w:hfuse.bin:r -U efuse:w:efuse.bin:r
</code>

(leave one part "-U ..." out to flash only a part).