danics 
Hi everybody, i m newbie in hardware and i have a strange problem i write a program for my device mini2440 for send and get data in text with RS232 communication,i write another similar program in XP so when i connect my device to my computer i can send and get data with this programs, but when i connect a Magnetic Card reader to my device i cant get any data from that,so i connect card reader to my computer and test with my program and its work and i get data from card reader, whats the problem here? when i m connect GND and VCC of card reader to pin 2,3 CON0 of mini2440, my device reset automatically,when i can use this 2 pins for getting power? thanks a lot