Hi Markl, Have you tried just Googling: `Sd card: detection switch connections` There seems to be some useful looking stuff comes back from that. :)

I did! :) Before I asked, I was thinking that I would put a pull up resistor to the A and connect the B output to a gpio pin of my CPU. That way, I should have an interrupt on card insert. Is there any flaw in my thinking? thanks ;)

Sorry about the delay in replying. If you look at: [https://www\.hirose\.com/product/en/download\_file/key\_name/DM3AT\-SF\-PEJM5/category/Drawing%20\(2D\)/doc\_file\_id/44099/?file\_category\_id=6&item\_id=06090031000&is\_series=](https://www.hirose.com/product/en/download_file/key_name/DM3AT-SF-PEJM5/category/Drawing%20%282D%29/doc_file_id/44099/?file_category_id=6&item_id=06090031000&is_series=) it shows the card detect switch as:    (The Hirose drawing is not great because there does not seem to be a corresponding   in the diagram.) If the diagram is correct however, you can connect either of the A or B pins to ground (or a supply) and then use a pullup (or pull down) on the other and then sense the voltage at the junction of the switch and the pullup (pulldown) resistor. This gives a very clear distinction between the voltage levels indicating the two states of card inserted and no card. It is safer to do that than to connect the switch in series between a pullup (or pulldown) and a GPIO pin because you would need a pulldown (or pullup) on the GPIO pin to ensure it does not float when the switch is open (i.e. no card inserted). This then reduces the voltage differnce between the voltage levels indicating the two states of card inserted and no card because when the dard is inserted you have a pullup fighting a pulldown. Be careful to debounce the sense input in some way to avoid false card registrations. :)