Voltage level

General discussion on mikroBasic.
Post Reply
Author
Message
pubinho
Posts: 23
Joined: 20 Dec 2007 16:11

Voltage level

#1 Post by pubinho » 10 Jan 2008 10:36

I have a new problem. I have a doubt:
I'm trying to communicate with my SD card through SPI. I have a easypic sd 4 powered by 5 V ( USB ).
Sd card wants 3.3 V. So I put a LM1086 CT 3.3 to feed Sd card.
My doubt is that I linked Portc to Sd card data lines, but line of portc are at 5 V( high level). Is this the reason why I can't try to initialize Sd ?
How can I solve this problem?
Top
alsopb
Posts: 217
Joined: 31 Oct 2005 00:56

#2 Post by alsopb » 11 Jan 2008 17:38

Try your SD card in some other device.

I fear you have destroyed it.

You can try a level shifting device called resistive divider to drive it. Perhaps 1.2k and 2.2k resistor in series. The output of the PIC goes to the top of the 1.2k, take the output to the SD card from the junction of the two resistors and ground the remaining 2.2k end.

The VR only is supplying voltage to the SD card, it doesn't shift input levels.
Top
pubinho
Posts: 23
Joined: 20 Dec 2007 16:11

thanks

#3 Post by pubinho » 11 Jan 2008 18:53

I tried to do a voltage divider a 270 ohm and a 430 ohm but it can't work.
Why this situation? Are these resistance too small?
Please answer me!!!!!
Top
pubinho
Posts: 23
Joined: 20 Dec 2007 16:11

#4 Post by pubinho » 11 Jan 2008 18:55

Sd still work.... I have not destroyed yet
Top
rmteo
Posts: 1330
Joined: 19 Oct 2006 17:46
Location: Colorado, USA

#5 Post by rmteo » 11 Jan 2008 19:17

See my reply here:

http://www.mikroe.com/forum/viewtopic.php?t=13098
Top
pubinho
Posts: 23
Joined: 20 Dec 2007 16:11

#6 Post by pubinho » 11 Jan 2008 19:28

U wrong, I saw a project with a sd card as datalogger with pic16f876, if it has spi interface it can work
Top
alsopb
Posts: 217
Joined: 31 Oct 2005 00:56

#7 Post by alsopb » 13 Jan 2008 03:15

Those resistors probably OK. I was trying to minimize the current.
PIC's have a maximum total device current limit.

Do an experiment. Set the port pin high and measure the voltage with the device attached. See that it is OK.

I haven't a clue about the current the device you're using draws.
Top
Copy'nPaste
Posts: 573
Joined: 25 Apr 2006 15:39
Location: Cape Town, South Africa

#8 Post by Copy'nPaste » 13 Jan 2008 09:23

Why don't you just download the schematic that the people from mE so very kindly supply on the website :evil: :evil: :?:
Your resistors are waaay to low in value :(
"Copy'nPaste"
Top
Post Reply

Return to “mikroBasic General”