AVR is RISC microcontroller familly, with JTAG interface implmentation members. This is powerfull debug acces, but you need to have special hadrware for this interface. Also JTAG connector have to be implemented on your target board. The goal of this project is to implement JTAG iinterface by the easiest way is possible into youtr target.

There is only one standart FT232USB driver, which is connected to JTAG pins of your target AVR processor. This FT232 is also used for standart serial communication. All job is done on your PC , which emulates JTAG interface via FT232 BitBang mode. This allows you to control fuses, memory lock bits and initial software downloading by one exe programm at your PC, via USB, without any external HW necessarity. The performance is not as original specialized JTAG hardware, of course, but is enough to be used as initial tool for download one of "bootloader" routines into new , "clean" AVR for first time and continue with this bootloader via USB serial link for future AVR Flash software upgrade ....

The connection is simple (Click at picture to see it in full resolution) :

Full KiCad schematics :


(You have to add libraries into your KiCad copy before you open schematics file.)

PC software for JTAG emulation via FT232 is here :

This software is not supported since there is new HappyJTAG2 version. Please check HappyJTAG2 page!