SD card problem

dynamitron · Joined: 18 Mar 2009 Posts: 38

Hello all,
I have a project where I must use a SD card under fat32.
For starting, I am trying to do simple things with mmcsd.c from the CCS library. I use a SD daughter card from Microchip (AC164122). This card is brand new.

I use this simple code just to test writing a value and read it back just after, it comes from the examples library : ex_mmcsd.c

I had no success getting the card initialized. To make sure the hardware is ok, I am watching the SPI signal with a scope and there? SDI (signal form the card to the pic) stay always at 0V.

What is wrong ? If anyone have some advice, I would be very interested to know it.

Thanks in advance for the answer.

Dynamitron.

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

In order to help you we need more info:
- What is your compiler version number?
- Which processor are you using?
- Describe your hardware connections, or even better post a schematic.
- The pull-up resistors are present on the data lines?
- What voltage is the PIC running?
- And what voltage the SD card?
- Do you get any output printed? What output?

Post a small example program demonstrating your problem. Even when you are using ex_mmcsd.c you would have had to make some modifications for your hardware setup.

asmallri · Joined: 12 Aug 2004 Posts: 1631 Location: Perth, Australia

dynamitron · Joined: 18 Mar 2009 Posts: 38

Thanks for the first answers.

Some more info :

Compiler version 8.40
Processor Pic 18F8722
Pic voltage 5V
Voltage of the SD card 5V (pic side), 3.3V (card side).

There is 10k pull-up resistor to 3.3V on the daughter card on the SD side.
SD and Pic are interfaced by level converters and everything is as provided by microchip

The code is from ccs exemple ex_fat.c and mmcsd.c

asmallri · Joined: 12 Aug 2004 Posts: 1631 Location: Perth, Australia

dynamitron · Joined: 18 Mar 2009 Posts: 38

Where do I find this inofrmation ? On the card itself ?

asmallri · Joined: 12 Aug 2004 Posts: 1631 Location: Perth, Australia

dynamitron · Joined: 18 Mar 2009 Posts: 38

I have a rev1 card, it is mentionned on the delivery sheet which comes with the card.

I have tried to use a C code from microchip compiled with their student compiler. A this moment, I see indeed that with the scope, the SDI is alive but still the card is not going to initialized state.
The soft is very hard to understand, I do not believe that I will be able to do anything with it. I probably must pursue with ccs.

Any hint before I start modifying the card with my soldering iron ?

asmallri · Joined: 12 Aug 2004 Posts: 1631 Location: Perth, Australia

dynamitron · Joined: 18 Mar 2009 Posts: 38

yes I saw it and it is my next move...
Thanks for this suggestion, I will let you know.