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Posted Jan 25, 2012 at 10:08 am
Figure 1
The circuit of AVR In-System-Programmer (ISP) has been modified to function with USB connection to a PC.
The modification of the old AVR ISP includes the replacement of two transistors which will be used to adapt the RS232 voltage levels to TTL voltage levels using USB to RS232 chip such as FT232BM. The source code was also modified to work with higher frequency crystal.
A few and ordinary components is required by the FT232BM to function. A serial EEPROM integrated circuit is used to store the settings of the user. When data is transmitted or received by FT232BM, the LED will start to flash. A USB-B connector and a 6-pin connector to the target AVR is required to be programmed. The target circuit is being supplied using a switch with 5V that comes from the USB connector of the PC. This removes the necessity of additional power supply for the target circuit since a single USB port can supply up to 500mA current. This current limitation should not be exceeded which includes the AVR programmer current requirement.
Using this AVR programmer in with Windows XP SP2 or later operating system will not require any driver.
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2 years ago: I recently came across your blog and have been reading along. I thought I would leave my first comment. I don't know what to say except that I have enjoyed reading. Nice blog. I will keep visiting this blog very often.
Susan
http://carusbcharger.com
2 years ago: I think the size of the PCB can still be reduced beacuse there are still enough spaces for the components to fit together with sufficient distance apart