■

http://bbqandbanjos.blogspot.jp/2012/03/arduino-com-usb-unknown-device-problem.html

hard リセットの仕方
https://learn.sparkfun.com/tutorials/pro-micro--fio-v3-hookup-guide/troubleshooting-and-faq#ts-serial

softwareリセット
Be aware of the automatic (software) reset
Reset arduino with code
1)///禁じ手///////これは fio v3を破壊するかもしれない///////
void software_Reset() // Restarts program from beginning
//but does not reset the peripherals and registers
{
asm volatile (" jmp 0");
}

void (softReset)(void){
asm volatile (" jmp 0");
}
2）//////////////////////////////////////////////////////
void reboot() {
wdt_disable();
wdt_enable(WDTO_15MS);
while (1) {}
}
//////////////////////////////////////////////////////
http://usemodj.com/blog/?cat=79

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1246541553
http://www.instructables.com/id/two-ways-to-reset-arduino-in-software/?lang=ja
http://www.xappsoftware.com/wordpress/2013/06/24/three-ways-to-reset-an-arduino-board-by-code/?goback=%2Egde_1268377_member_252364609

2)
http://arduino.cc/en/Main/ArduinoBoardFioTips#.UxJV4ON_t8E
void setup() {
Serial.begin(57600);
Serial.print(255);
}