Micro SD PMOD Question

[hlittle]

Hi,

Can anyone confirm or deny that the micro sd pmod allows the fpga to power cycle the sdcard?

The schematic seems to imply that the functionality is supported, but it says the parts are not loaded. However, in the pictures of the pmod, it looks like the parts are present (everything seems to be there, except for R6 and R15, zero ohm resistors). So there is an inconsistency there.

Do the pmods come as pictured? And if so, is it correct that I would need to just add R6 to enable the powercycling capability?

Thanks

[JColvin]

Hi @hlittle and @D@n,

The Pmod MicroSD card came in; the schematic is accurate with regards to the circuitry not being loaded. The pads and silkscreen are still present on the underside of the module (if you wanted to load the components yourself), but they are not populated in the production version.

I attached a couple of pictures of the module with my poor photography skills; I will put in a request for an official photo of the underside to be taken for the Resource Center and store page.

Thanks,
JColvin

[JColvin]

Hi @hlittle,

I am in the process of ordering a Pmod MicroSD card for myself to see what is loaded on it; I talked with the design engineer and from what they guessed (since it has been too many years for them to remember designing this module) that the picture and the modules that my co-worker has were actually prototypes of Rev A.0 that still previously had this circuitry loaded on the device before its (theoretical) removal in A.1.

I will be able to let you know with certainty what to expect on a Pmod MicroSD sometime next week.

Thanks,
JColvin

[D@n]

From the reference alone, there are no pins left to turn on or off the power.  You have the pins you need to control the SD card, but not to power it up or down save by unplugging it.  You might wish to look into sending a reset command to the device, but controlling power is off the table.

Dan

[hlittle]

@JColvin, thanks.

@D@n, With the *micro* sd pmod, pin 10 is potentially connected to the enable line of the power regulator. The reference does list pin 10 as NC, but the schematic suggests that it could be used to power cycle the sd card, if that part of the circuit is present :-)

The Nexys A7 board has the ability to power cycle the on-board micro sd card. I am just wondering if that feature exists with the pmod too.

My hope was to use the power cycle as an fail safe reset in case the sd card got into an uncooperative state.

Without the ability the power cycle the sd card, what's the next best way to reset an sd card (in spi mode)? Is toggling the chip select line and sending cmd0 the best we can do?

[D@n]

@hlittle, Thanks for pointing out the difference!  I now see what you are talking about.  The "write-protect" pin from the PModSD is now an NC on the PMod Micro, but the schematic shows that a circuit might be populated ... got it.  I'll look forward to hearing the answer as well.

Dan