Vermes
Advanced Member level 4
Presented project is a simple system of AVR programmer. It allows you to program the internal memory of AVR microcontrollers. Construction is based on a really popular solution used all over the world – STK200 programmer. The main features of the systems are the simplicity, low cost and trouble-free launch. The programmer is supported by the best-known programs such as Bascom AVR, Avrdude PonyProg and many others. The use of buffer HCT244 increases safety of work with a computer in relation to the direct connection of the microcontroller to the LPT port. Risk of damage to the port by the assembly errors of prototype systems falls significantly. Buffering the programming signals allows to work on a long cable and additionally eliminates the programming errors.
Scheme:
System U1 74HC244 acts as the buffer that ptorects the computer port against damage. Diode D1 (1N4148) prevents from damage in case of reverse connection the programming supply voltage. Resistor R1 (100k) forces high state at the buffer input. When the programmer is disconnected from the microcontroller, that prevents from transient states. Capacitor C1 (1uF) filters the supply voltage. Diode D2 and resistor limiting its current R2 (470R) work as the supply indicator. Connector CON1 (DB25M) allows to connect the programmer directly to the LPT port in a computer or any cable.
Pictures:
Board: http://mirley.firlej.org/files/STK2_Plytka.pdf
Link to original thread (useful attachment) – Programator STK200, programator AVR