ubuntu_amateur
Member level 4
there is a circuit to detect a 5V power supply via parallel port, pls take a look at the attachment.
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when Power Supply is present, parallel port input will detect Low level.
when Power Supply is absent, parallel port input will detect High level.
usually, if there is no this circuit, read parallel port will get 0x7F at address 0x379.
if this circuit is connected to parallel port, the circumstance is not improved.
the value of reading parallel doesn't change, even if the resister Rb2 is removed.
what's wrong with this circuit? Anyone help figure it out?
[/img]
when Power Supply is present, parallel port input will detect Low level.
when Power Supply is absent, parallel port input will detect High level.
usually, if there is no this circuit, read parallel port will get 0x7F at address 0x379.
if this circuit is connected to parallel port, the circumstance is not improved.
the value of reading parallel doesn't change, even if the resister Rb2 is removed.
what's wrong with this circuit? Anyone help figure it out?