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Card Detect on Panda I SD Card header


I am trying to understand the pins on the header as I would like to get card detect enabled. I am not using the GHI SD Card board but a 9 pin board with CD. The 8 other pins [ Dat0-3, CMD, VDD, GND, CLK] hook up fine and the basic read write samples work (with a Thread.sleep(1) to enable the unmount without an exception).

What pin if any should I connect CD to?

I am struggling to understand IO4/PWM. The USBizi manual says that On power up, this pin is used to select the communication interface for GHI boot loader and debugging. So what purpose does it have for SD Cards?

Out of interest what is IO46* power enable signal for?



IO4 is the MODE pin. At boot time (before your app starts!) it’s checked to see what debugging to use. It doesn’t have any impact on your app when it’s running, and it doesn’t have any direct impact on the SD card. It can be used in your app as a PWM pin, as ain interrupt input pin, or as a general IO pin.

I’d suggest you use IO4 as your CD pin :slight_smile: Unfortunately, you’ve got to implement the code for sensing CD yourself.

Power Enable must be a SD or MMC card specification / requirement, but i have no idea either what it is for or how it’s used.


It has nothing to do with SD and shouldn’t be used as card detect because of special nature.

You can use any other IO for card detect.


If you look at the schematic of the Panda2 or the Domino then you will see that the Power Enable pin is used to turn the power to the SD card on and off. This is purely for power saving and isn’t required… :slight_smile:


The USBizi manual says that IO43 should be used for card detect, as it is on the Panda II. IO43 isn’t broken out on the Panda I

Maybe I’m being slow but why was IO4 put on the SD Card header on the Panda 1, when it seems IO43 was the right one.

Also was it CD on the Micro SD Card Expansion board?



Card detect is just an IO, it is high when no card is inserted and low when it is inserted. IT can be connected to anything. We may have connected it some pin one board A but that doesn’t mean it will be on the same pin on board B. Did I answer your questions?


uSD doesn’t have a detect IIRC - at least on the samples I’ve seen they didn’t, and the GHI board doesn’t have it on the connector…


thanks for the answers and help.
I’ll use another pin for my project on the Panda I (& I’ll get a Panda II soon for future projects!)

Gus I didn’t mean any criticism of the products or changes between them. They are such a good platform for a beginner.



I know, I was only explaining :slight_smile: