SD Socket, Write Protection and Card Detection?

rwgast_logicdesign

Ok so a while back i just soldered and sd card to some headers, I haven't had the need for SD before today and realized theres no way I wan Insert that SD card soldered to headers into my pc... the hole header idea looks cool and thrifty but its kind of useless. Anyways I have some molex SD socket, problem is I dont know the part number or anything about them, but Im assuming there fairly standard without card detection since theres 9 pins. This is what I have put togather so far

Image

Now I was going to attach 10k pull ups to be on the safe side, then I started thinking is there any way to do card detection and most importantly write protection detection by adding some components. Ray says he can do card detection with 4 resistors but i looked at his PSM document that he refers too and the schematic in the SD section doesnt show anything except connections on p0-3.. That also doesnt take care of the write protection either.. just thought id check before i start soldering things togather. I would think card detection could easily be done via software but i have no idea how to check the wp tab..

Kye

Please check the schematics within. http://www.parallaxsemiconductor.com/sites/default/files/appnotes/AN006-SD-FFS-Drivers-v1.0_0.pdf

Thanks,

rwgast_logicdesign

thanks for the app note i will look at the schematic. i plan on writng my own drivers in pasm. i want to try to get at least a 20mhz clock so i can attempt to add some sram on the same bus.

when building this thing i realized i wanted a status led would the best way ti achieve that be to tie an led to the cs line or the io lines?

rogloh

I would just hook the LED to the CS line on the SPI bus via a suitable series resistor to the supply voltage to limit the LED current. Then when CS drops low to read or write the SD card it will light your LED to show activity. If you use the clock or data out lines from the prop instead of CS it would still light up the LED but the LED would be dimmer and/or flicker more as the signals flip from high to low in each SD transaction. The data in line should certainly not be used for this LED. Make sure you choose your resistor to not load the CS pin with too much current so as to overload the capacity of the prop IO pin. A few milliamps at most should just about suffice for a small LED these days.