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--- flash_the_atmega [2013/10/05 11:29] – breaker27
+++ flash_the_atmega [2023/03/01 19:40] (current) – [Using flash scripts] breaker27
@@ Line 1: / Line 1: @@
 ====== 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. If you take the prebuilt package, extract it to a directory of your choice.
+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:
@@ Line 13: / Line 25: @@
 Be sure about the fuse settings you want to write in your microcontroller. With wrong fuse settings, your microcontroller might not be accessible anymore!
-====== Programming your own fuses ======
+===== 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:
@@ Line 23: / Line 35: @@
 (replace ?? by the hex value for the needed fuse settings and use "lfuse", "hfuse" or "efuse" accordingly).
-====== Flashing the controller ======
+===== 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
+xfc != 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 =====
@@ Line 31: / Line 57: @@
   * **flash.cmd** / **flash.sh** for flashing firmware, eeprom and fuses
   * **flash_firmware.cmd** / **flash_firmware.sh** for flashing only the firmware
-  * FIXME: The Linux scripts do not exist yet.
-===== Calling avrdude directly =====
+===== Using a make rule =====
-If you want to call avrdude by hand you can flash everything with:
+If you have the source code on your machine, you can flash the firmware with the following command from the firmware subdirectory:
 <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
+make program
 </code>
-(leave one part "-U ..." out to flash only a part).
+===== Calling avrdude directly =====
-You should only write the fuses once. **And in general, it's a good idea to only flash what you need to, because there is a limited amount of possible flash cycles.**
+If you want to call avrdude by hand you can flash everything with:
-===== 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
+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).