1# Flashing firmware externally supplying direct power 2 3**WARNING:** Never use a high current rated power supply, like PC ATX power 4 supply. It'll literally melt your PCB traces on short circuit. 5 6On some mainboards the flash IC Vcc pin is connected to a diode, which prevents 7powering the rest of the board. 8 9![][flash_ic_diode] 10 11Please have a look at the mainboard specific documentation for details. 12 13On those boards it's safe to use a programmer and supply power externally. 14 15**WARNING:** Verify that you apply the correct voltage! 16 17## USB programmer 18USB programmers are usually current limited by the host USB hub. On USB 2.0 19ports the limit is 500mA, which is sufficient to power the flash. Those are 20the best choice as they are stateless and have a fast power on reset cycle. 21 22## Single board computers (like BeagleBone Black / RPi) 23Be careful when connecting a flash chip, especially when using a Pomona 24test-clip. A short circuit or overcurrent (250mA) causes a brown-out reset, 25resulting in a reboot of the running operating system (and possible loss of 26remote shell). 27 28[flash_ic_diode]: flash_ic_diode.svg 29
