SPI\SD Card Query - Page 3 - Electronic Circuits Projects Diagrams Free

DirtyLude · 22nd January 2009, 01:33 PM

I still haven't figured this out. I even pulled the shield off of the card slot to make sure the contacts were touching the right spots on the card and detect continuity all the way from the contact to the uC pin.

I'm going to leave this for a while and work on some other projects.

I realized my setup picture above points to my Logic analyzer screen shot.
http://www.higginstribe.com/z8e/sdcard-encore-setup.jpg

UTMonkey · 22nd January 2009, 01:47 PM

Quote:

Originally Posted by blueroomelectronics

Well you will need a level shifter when using the SPI in hardware for the SDI pin. 3.3V is just not high enough for the Schmitt inputs on a 5V PIC. I'd have to check the datasheet but I recall it's something like VCC-0.8 (4.2V) is a 1.

Hi Bill,

I have had a look at the data sheet but the page doesnt make a lot of sense.

What does it mean?

Thanks

Mark

AtomSoft · 22nd January 2009, 02:02 PM

To better explain that page. It basically shows you the voltage at any given pin (left side aka characteristics) .

So you look for the pin in question in this case I/O PORTS (Except RC4/RC5 in USB MODE)

Then you figure out if its a SCHMITT PIN or TTL or is it RC3 and RC4

If its a SCHMITT pin then the LOW = VSS to .2 from VDD (1v)
The SCHMITT pin HIGH = .8(4v) from VDD to VDD itself (if a pic with 5v source then 5v)

As bill said below:
.8v * 5v = 4v (HIGH)
.2v * 5v = 1v (LOW)

blueroomelectronics · 22nd January 2009, 02:05 PM

It means 0.8 * VCC is a logic high for schmitt inputs

4V with a 5V VCC

UTMonkey · 22nd January 2009, 08:49 PM

Thanks Jason and Bill.

DirtyLude · 26th January 2009, 02:27 PM

I found my problem. Phase was set incorrectly, so it was clocking data in and out on the wrong edges. I knew it was something stupid like this.

Thanks for giving it a look.

UTMonkey · 27th January 2009, 09:44 PM

Quote:

Originally Posted by blueroomelectronics

Remember the SPO on the SD card is driven not open collector so pullups won't help.

Sparkfun uses this design on one of their level converter designs.

Ok, just pretend I know very little about electronics (there already? good

).

I have just grabbed a spare breadboard and wired up the above circuit with a 5 volt and 3 volt regulator, I wasn't able to source a BSS138 but used a 2N7000 (literally because they are both n-channel mosfet - I still don't understand mosfet operation at all)

With a multimeter and with no inputs on TX-3.3V I measured 3.3 volts on TX-3.3V and 5 volts on TX-5V.

Is this correct? I am guessing yes, but please correct me.

Next, I ground the TX-3.3V . I now measure 0 volts on TX-3.3V and 0 volts on TX-5V.

Is this correct? is this what Bill described as:-

Quote:

the SPO on the SD card is driven not open collector

Thanks in advance.

Mark

blueroomelectronics · 27th January 2009, 11:29 PM

Sounds perfect.

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22nd January 2009, 01:33 PM	#31
DirtyLude	I still haven't figured this out. I even pulled the shield off of the card slot to make sure the contacts were touching the right spots on the card and detect continuity all the way from the contact to the uC pin. I'm going to leave this for a while and work on some other projects. I realized my setup picture above points to my Logic analyzer screen shot. http://www.higginstribe.com/z8e/sdcard-encore-setup.jpg __________________ Mark Higgins

22nd January 2009, 02:02 PM	#33
AtomSoft	To better explain that page. It basically shows you the voltage at any given pin (left side aka characteristics) . So you look for the pin in question in this case I/O PORTS (Except RC4/RC5 in USB MODE) Then you figure out if its a SCHMITT PIN or TTL or is it RC3 and RC4 If its a SCHMITT pin then the LOW = VSS to .2 from VDD (1v) The SCHMITT pin HIGH = .8(4v) from VDD to VDD itself (if a pic with 5v source then 5v) As bill said below: .8v * 5v = 4v (HIGH) .2v * 5v = 1v (LOW) __________________ AtomSofts eBay Store AtomSoftTech: C18 TIPS & TRICKS v9 PDF Nokia 6100 Driver/Software My Name: Jason Lopez http://atomsofttech.info/ \| My YouTube Videos! My Favorite Store: dipmicro Electronics Last edited by AtomSoft; 22nd January 2009 at 02:13 PM.

22nd January 2009, 02:05 PM	#34
blueroomelectronics	It means 0.8 * VCC is a logic high for schmitt inputs 4V with a 5V VCC __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/

22nd January 2009, 08:49 PM	#35
UTMonkey	Thanks Jason and Bill.

26th January 2009, 02:27 PM	#36
DirtyLude	I found my problem. Phase was set incorrectly, so it was clocking data in and out on the wrong edges. I knew it was something stupid like this. Thanks for giving it a look. __________________ Mark Higgins

27th January 2009, 11:29 PM	#38
blueroomelectronics	Sounds perfect. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/