Instructions Circuit Diagram

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Loading a program
How do we load a program into the microcontroller’s ‘Flash’-memory?
Normally you would need a special programming device, equipped with
an IC-socket, in which you would insert the microcontroller-chip. The
programming device allows you to transfer the program directly into the
microcontroller’s ‘Flash’-memory. The programming device is named
‘programmer’.
Using the ‘programmer’ normally implies providing the YETI with some
connector and cabling system and connecting the YETI with the ‘pro-
grammer’ to load a new program or program version. However a few
clever engineers at DLR (www.dlr.de) were able to develop and provide
us with a smart programming tool.
This smart tool does provide a permanent small piece of software in
the microcontroller’s ‘Flash’-memory, called the ‘Bootloader’.
Immediately after switching on the microcontroller’s power supply the
microcontroller will always check whether a ‘Bootloader’-program is
available in the ‘Flash’-memory. If the program is available, the micro-
controller will execute this ‘Bootloader’-program.
Now pay attention:
The ‘Bootloader’-program has been designed to communicate with the
YETI by infrared transmitter and receiver modules. Communications
require special software at a PC. This software is called ‘Flash’ and
may remind you of the name of the microcontroller’s memory. Of
course the PC will have to be equipped with equivalent infrared trans-
mitter and receiver modules.
The bootloader and the ‘Flash’-program will start communicating and
the ‘Flash’-program will now start sending a YETI-program to the
‘Bootloader’ instruction by instruction. The bootloader will receive the
instructions one by one and will put them into its ‘Flash’-memory. Of
course the storing process will not overwrite the memory area, in which
the ‘Bootloader’ is stored. Instead the received program will be stored
in the memory area next to the ‘Bootloader’-program.