Pmod SD: Full-sized SD Card Slot

[TonyIta]

Dear all 

I am trying to interface this d Pmod SD: Full-sized SD Card Slot

I can not understand very well the schematic. Please someone can help?

Basically i can not understand the MISO input is attached to a 100k resistor to VCC -------Vcc-------100k ohm ----------PICMISO/Data0DO. See link below. I was wondering if someone can help me to understand what it is for.

I have also another question please. I am interfacing the Pom unit to a microchip Explorer 8 Development Board using the  PIC18F87 it runs a 3.3 V and 5V . Assuming it runs at 5 volt and the Pom runs a 3.3V. is this configuration ok for that or i should add  a sifter voltage 

Thank you so much for your time 

Cordially 

Antonio 

 

[JColvin]

Hello @TonyIta,

The Pmod SD is configured as such because the SPI communication with an SD card is a subset of the SD Card Memory protocol, and so the MISO line is connected to the Data0 line on the physical SD card slot. More details about this can be found in the specifications provided on the SD associations website here.

Based on the schematics for the Explorer 8 Development board, it appears you may be able to use jumpers J15 and J16 to adjust the supplied voltage to the Pmod ports to 3.3V rather than 5V. If that is not an option with the PIC18F87, then yes you will need to implement some sort of level shifter, otherwise you will likely damage any connected SD card.

Thanks,
JColvin