Pic 18f4550 interface SD card isn't working with lib ex_fat

[kideltn]

After simulation Proteus interface with SD card but fail

[petiot]

shouldn't your resistors on SDA and SCL pull up to not down?

[Ttelmah]

You need a level translator chip on the incoming data line from the SD card.
Given the minimum supply voltage for the 4550, is 4.2v, the voltage required for a 'high' on the SDI line, is 3.36v or more (if the supply voltage is higher). The SD card, only guarantees Voh to be the supply *0.75 (2.25v, with the 3v supply shown), the PIC is not going to see any 'high' data on this line....

Best Wishes

[kideltn]

Thanks for reply !
I used schematic from

and change pin to match 18f4550.
I don't understand Ttelmah,

[Ttelmah]

The problem is voltage levels.
If you use a PIC that runs off 3.3v, and run both the PIC, and the SD card off this voltage, then both are using the same logic 'levels', and will co-exist fine. What you have is a PIC running off a higher voltage, and because of this it both outputs higher voltages than the SD card can take (easily handled with resistors), and wants higher voltage _inputs_ than the SD card generates. This later is not do-able with resistors, but instead needs a level translator of some sort. The 'logic levels' change with different voltage supplies.
Now, PIC inputs, have two different voltage levels required, according to whether you use 'Schmitt' inputs, or 'TTL' inputs. The Schmitt inputs, have a Vih specification, of 0.8*Vcc. So for a 5v supply, 4v is _required_ for a high to be seen. The TTL inputs have a specification at 5v, on the 18F452, of 2v required for Vih. A lot lower. It is possible to run without buffers, by using sofwtare SPI, on pins without the Schmitt inputs. However the circuit you show is not doing this, and won't actually work reliably.
A search here, will find many dozens of past posts about this. It is not a PIC/SD card 'thing', since using a low voltage PIC solves the problem, but a general 'mixing logic families of different voltages' thing. You wouldn't expect a piece of equipment designed for 220v, to run on 110v supplies without an adapter, and the same applies when you mix supplies on a PCB....

Best Wishes

[kideltn]

Thanks you again!
Really, my major is coder and my project involved sd card. I'm beginner in electronic and thanks for your explanation to help me a lot.
I read datasheet 18f4550 and decide change pin as figure:

I changed SDO to RB4 (RB4 has input TTL).
But I really am not confident with above figure.
Can you consult me it !
Thanks a lot !

[Humberto]

You need to add a 3-10K pull up (to +5V) in DO line.

Humberto

[asmallri]

If you go to my projects page there are operational examples demonstrating how to integrate and SD card with a 5 volt PIC with resistor dividers on SDI, CLK and CS of the SD cards. For a production project you need a level translator between the DO of the Card and SPI of the PIC but for a proof of concept you will find it will work ok without it but the SPI PIC input will be operating out of spec. You also need the pullup to 3.3 volts on the DO of the card as already discussed.

While it is technically possible to implement a software SPI interface to the SD card as you have done, it is not generally a good idea. You need to take into account the shear volume of traffic that needs to be exchanged between the PIC and the SD card just to do a directory lookup.
_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

[ckielstra]

Things become a lot easier when you use a PIC18 model that can run at 3.3V.
Why not use the PIC18LF4550? (L = Low voltage)
Or one of the many other PIC18 chips?

[asmallri]