Imp + SD card reader, what would it do?

Curious to find out, but before I break my Imp or an SD card reader…
Any idea what would happen or what could be done with it?

Hugo said in one of the presentation videos that nothing will happen if IMP accidentally is inserted into a SD reader.

All I can see from the drawings that the VCC and GND are the same like in the case of the SDCard but a major difference is that one of the GND’s (SD has two GND pins) is used as a GPIO. Don’t know what happens if the IMP is powered up and has a firmware which automatically rises that pin up to logical 1. It might be that this can’t happen and no firmware is started ever if the dedicated serial number pin does not works (no id chip there).

Anyway You should wait for inside answer before blowing up something :slight_smile: I am also curious …

Hugo has a very honest face so I popped an imp into my laptop SD slot. Nothing exploded. Both imp and SD reader remain functional.

I believe they left open the possibility of programming an imp to emulate an SD card, which I would very much like to see as an alternative to the flashy app method of programming. An API class to log data to local “disk” would be cool too, for applications where the imp will be out of WiFi range for a while.


Good to know.
Is there any mention of being able to dual purpose an SD card slot? I’m guessing it would all be a matter of software on the device side, changing the function of the SD card data lines…

Being able to use the Imp for data logging and limited storage would be great, I already have an SD for that…

Any SD slot will have pin 6 grounded, and this pin is an open-drain line to communicate with the ID chip; if the line is low at powerup, the imp assumes it’s in an SD slot and just… does nothing.

We have had the imp pretending to be an MMC card in the past, so the hardware is capable, but no plans to actually implement this functionality right now. One issue is that some hosts are very aggressive on their power control and will power down cards when idle, which isn’t ideal for us :slight_smile:

What about the opposite?
Can I insert an SD card into April impee and still have a functional SD card when I remove it?

@ZPM: if you wanted to dual purpose a slot in your product, and have a spare UART or I2C, you can do this:

Put the ID chip on pin 6 as usual, with a host-side pull up. If you see a card inserted and this line is high, then there’s an imp there and communicate using a UART or I2C on pins 8 & 9.

If you see a card inserted and this line is low (as cards also tie both grounds together), it’s a memory card and you can use MMC or SPI protocol to access it on the usual pins (standard arduino type interface).

The same technique can be used to prevent errant behavior when an SD card is inserted into an imp slot, if so desired (low pass filter pin 6. High=imp, low=MMC/SD).

Sorry to bring up an old thread, Hugo are you saying its possible to build an impee with a slot where we can insert either an imp or an SD card for say remote (cloud) or local storage respectively?

Yep, you could.