MicroSD Cards and SDFS

[mackrackit]

SD cards have 9 pads.
Looking at the pads and the pads towards you the right hand pad is #9(the pad on the angle). From there they then going from right to left 1 to 8

The other three connections from the socket are a common, Write Protect, and Card Detect.

SD pads 8 and 9 are pulled high (3.3 volt) with a 10k.
Pad #4 is 3.3 volt.
Pads 3 and 6 are VSS.
Pad #1 is Chip Select, CS
Pad #2 is Data Out from PIC, into SD.
Pad #7 is Data In to PIC, out from SD.

[rsocor01]

mackrackit,

Thank you for your response.

SD cards have 9 pads.

All the MicroSD cards that I have seen so far have 8 pads. Look at the attached picture.



Can I use SDFS with MicroSD cards that have 8 pads? From searching in google, I found that these MicroSD cards can operate in two modes, SPI and SD modes. Please take a look at the attached pics.



What mode should I use? How do you relate the pin functions to the schematics in the SDFS help file?


Robert

[Normnet]

Just a guess but use an adapter and SPI mode is by far most common.

Norm

[mackrackit]

Doh.... I was thinking regular SD cards.

The only time I have used them was with an adapter so using one straight should not be a problem.

Looking at the pin outs between the two it appears pin 9 has been dropped and pin 1 is not used on the micros. Pin 2 on the micro is the same as pin 1 on the full size, I think. Just compare the pin names and functions between the two.

SPI.... That is what SDFS uses. The only option it hardware SPI or not. Testing for speed between the two I have not seen a difference. Hardware SPI on the chip I use is also one of the USART pins so I have been using software SPI.

[rsocor01]

Hi,

I will use the SPI mode for the SDFS as you guys suggested. I've already ordered my MicroSD socket from mouser. So, I will keep you posted if I get it to work or not.

About all the extra pins that the MicroSD card doesn't use like the WP, I guess that I can comment out these lines of code that I don't need in the SDFS program. I'm going to have to study this SDFS code to see how it works.

Robert

[mackrackit]

When not using Write Protect do a search through SDFS for "SD_WE" and comment out anything to do with it. It only shows up in about 6 places.
Comment this

SD_WE_TRIS = 1

And all occurrences of this

If (SD_WE) Then
        FAT_error = CE_WRITE_PROTECTED
        Return        ' Return Byte FAT_error.
    Endif

The PIC® pin assignments will look something like this

SDI        Var    PORTB.2    ' SPI data in SD #7
SDI_TRIS    Var    TRISB.2    ' SPI data in direction
SCL        Var    PORTB.1    ' SPI clock  SD #5
SCL_TRIS    Var    TRISB.1    ' SPI clock direction
SD_CS        Var    PORTB.3    ' SD card chip select SD #1
SD_CS_TRIS    Var    TRISB.3    ' SD card chip select direction
SD_CD        Var    PORTB.4    ' SD card detect
SD_CD_TRIS    Var    TRISB.4    ' SD card detect direction
SDO        Var    PORTC.7    ' SPI data out   SD #2
SDO_TRIS    Var    TRISC.7    ' SPI data out direction

If you are not using the hardware SPI from the PIC® and need to use other pins put this in your code

SDC_UseHardSPI = FALSE

If you run into problems let us know.

[rsocor01]

If you run into problems let us know.

Thank you. As soon as I get the parts, I will start playing with the SDFS and the MicroSD card. I am sure I will have some questions.

Robert