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There is a Card Detect pin on most SD Card connectors, it gets pulled to ground when SD card is inserted. My question, is there a way to drive an LED as a status indicator using this GND signal. I am using SD 4 bit to interface with the host. Also using a 3.3V power rail.

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    \$\begingroup\$ Other than treating it as a normal switch? Because that's all it is. A switch. \$\endgroup\$ – Ignacio Vazquez-Abrams Dec 8 '15 at 4:14
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Something like this would be fine I imagine

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ So are you suggesting I use p-channel MOSFET at the switch, in that case should I be worried about polarity with respect to the LED? \$\endgroup\$ – tilengneer Dec 8 '15 at 13:41
  • \$\begingroup\$ The switch in the diagram is just representing the chip select pin on your SD connector. When there is no card in there, the pin is not connected to ground, so the circuit is open and the LED is off. When there is a card in there the pin is connected to ground, completing the circuit and turning the LED on \$\endgroup\$ – ElecEnthusiast Dec 8 '15 at 22:17
  • \$\begingroup\$ I am not using the chip select pin to drive the LED you make use of CS when you use SPI to interface with the host, am using SD 4-bit to interface with the host that's why i am inclined to use Card Detect on the connector to drive the LED. \$\endgroup\$ – tilengneer Dec 9 '15 at 16:47
  • \$\begingroup\$ sorry i meant to say card select not chip select \$\endgroup\$ – ElecEnthusiast Dec 9 '15 at 22:18

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