Picbasic MMC SD : sdfs3.bas

[mackrackit]

Card present is just a switch. I do not use that myself. You could put anything in the socket and make the LED light.

It is used with SDFS if you want to detect a card and force the code to re-initialize for a new card with out a power cycle, "hot swap".

At this time do not use it. Just more stuff to debug.

If you have an 18F4550, or equivalent, to connect like the example might also be a good place to start.

[Bruce]

Just a quess since I don't have your hardware to test;

With the card operating on 3.3V and the PIC on 5V, you should change to a port with
TTL inputs. Or use some type of buffer, or a PIC that will operate on 3.3V at whatever
osc speed you need.

PortC on the 18F452 are Schmitt Trigger type inputs that need higher threshold voltages
for logic 1 than TTL inputs.

[iw2fvo]

Hi Bruce,

I do have a resistor voltage divider 1k8_3K3> to gnd for the signals that go from PIC to MMC. The MMC output goes directly to PIC input portc.4 pin 23.
Could be that the card output level it is not enough to be reconized by the PIC s/t input....
I will really try with a level shifter and 18f452.
Any suggestion for a DIL ( not SMD ) device to be used for voltage shifting ?
Thanks a lot for the help.
Regards,
Ambrogio

Just a quess since I don't have your hardware to test;

With the card operating on 3.3V and the PIC on 5V, you should change to a port with
TTL inputs. Or use some type of buffer, or a PIC that will operate on 3.3V at whatever
osc speed you need.

PortC on the 18F452 are Schmitt Trigger type inputs that need higher threshold voltages
for logic 1 than TTL inputs.

[Bruce]

Hi Ambrogio,

Page 10, Figure 2 is a really simple bi-directional level shifter for 3.3V to 5V systems.
http://www.standardics.nxp.com/suppo...df/an97055.pdf

If you have a couple BS170 or similar on-hand, this one works, and it's cheap.

[iw2fvo]

Bruce,
it is a clever and inxpensive system.
If I am not wrong, I do have to put the level shifter from the data out of the card ( pin 7 ) to the input of PIC (pin 23) that has a higher VinH because of the S/T input type. It is more than 3v3.
I will have the BS170 by monday evening.
Additional question: where can i found the MMC digital interface declaration ?
I will like to examine a time history diagram from which I will learn to do with simple instruction ...
> when the SS has to be set hi or lo?
> same thing for SI, SO, CLK and so on . At the moment I am not able to find those kind of information .Those data are normally declared for all type of IC's I used up to now : where are the mmc interface data history ?
Thanks very much
Ambrogio
North Italy

Hi Ambrogio,

Page 10, Figure 2 is a really simple bi-directional level shifter for 3.3V to 5V systems.
http://www.standardics.nxp.com/suppo...df/an97055.pdf

If you have a couple BS170 or similar on-hand, this one works, and it's cheap.

[Bruce]

I'm not 100% sure if this what you're looking for, but Jan Axelson has a book titled
USB Mass Storage that covers MMC & SD cards.

http://www.lvr.com/usbmstoc.htm

Scroll down the page for a list.

You might also want to signup at http://www.jedec.org if you're looking for manuals, docs,
etc.

[iw2fvo]

Hi to all in the forum ,

Before starting with the hardware changes, I try with a program found on the web. I modified it for my hardware and it seem to me it is at least initializing the MMC properly.
The program is : MMC_POST[1] from Gary Warner. The modified one is attached. you can also find attached the terminal screen capture.
My system does not have the external EEPROM so i think this is the reason for which it does not go on...
I think it was not an hardware problem : >> What do you think ?
I will modify the program to avoid external EEPROM to see if it goes on.
Any comment ?
Thanks
Bye
Ambrogio
North Italy

I'm not 100% sure if this what you're looking for, but Jan Axelson has a book titled
USB Mass Storage that covers MMC & SD cards.

http://www.lvr.com/usbmstoc.htm

Scroll down the page for a list.

You might also want to signup at http://www.jedec.org if you're looking for manuals, docs,
etc.

[iw2fvo]

I do not have the pic18f4550 in m hands now.
Do you use the SDFS program or do you have other programs in basic ?
Have you a timed bit interface declaration for the MMC SD ?
Any time history diagram available just to try with a simple comands and response? Where can I found it on the WEB ? I will like to try with a very simple program ...
I will order that PIC but it will require some time.
Do you have in mind some kind of level shifter DIP ( not SMD ) to be used ?
Thanks
Ambrogio

Card present is just a switch. I do not use that myself. You could put anything in the socket and make the LED light.

It is used with SDFS if you want to detect a card and force the code to re-initialize for a new card with out a power cycle, "hot swap".

At this time do not use it. Just more stuff to debug.

If you have an 18F4550, or equivalent, to connect like the example might also be a good place to start.