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