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boraciner
Joined: 29 Jul 2009
Posts: 9
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 Posted: Sat Jan 16, 2010 5:29 pm |
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ok sir, I understand now.
I'll try to find 74HCT125(dip) thanks a lot !! |
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boraciner
Joined: 29 Jul 2009
Posts: 9
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| Posted: Sun Jan 17, 2010 5:59 am |
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| I see a level translator on this board ????? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Jan 17, 2010 11:47 am |
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The level translator chip only goes one way. It only shifts from +5v
CMOS levels down to +3.3v CMOS levels.
The "DO" signal from Connector J1 goes directly to pin 7 of connector J2.
There is no level translation on that signal. You need an external
level shifter chip to translate the 3.3v CMOS levels up to +5v CMOS levels. The PIC requires 5v CMOS levels on its SDI pin.
Schematic:
http://gravitech.us/MicroResearch/Others/MICROSD-ADP/MicroSD-ADP_Schematic.pdf |
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asmallri
Joined: 12 Aug 2004
Posts: 1634
Location: Perth, Australia
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| Posted: Mon Jan 18, 2010 9:21 pm |
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Anyone using this schematic as a reference should be aware that additional pull resistors are required. Unused Dx lines from the SD/MMC cards require pull-ups resistors as does the DO line from the card and the CD from the card socket.
The DO also needs a level converter (in theory) to meet the worst case Schmidt trigger input levels on the PIC input pins for the SPI port when the SPI peripheral is used.
_________________
Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!! |
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karsia
Joined: 26 Feb 2010
Posts: 5
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| Posted: Sat Mar 13, 2010 3:44 am |
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18f4520 can detect 2volt even from the ttl buffer if suplly range is between 4.5 and 5.5 . You can check it from datasheet ( DC CHARACTERISTICS input low voltage- input high voltage-page 335 ).
probably most of pics can detect this. |
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asmallri
Joined: 12 Aug 2004
Posts: 1634
Location: Perth, Australia
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| Posted: Sat Mar 13, 2010 9:03 am |
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| karsia wrote: | 18f4520 can detect 2volt even from the ttl buffer if suplly range is between 4.5 and 5.5 . You can check it from datasheet ( DC CHARACTERISTICS input low voltage- input high voltage-page 335 ).
probably most of pics can detect this. |
When configured for SPI mode, the pin is operated in Schmitt input mode not TTL mode.
_________________
Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!
Last edited by asmallri on Sat Mar 13, 2010 2:16 pm; edited 1 time in total |
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karsia
Joined: 26 Feb 2010
Posts: 5
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| Posted: Sat Mar 13, 2010 2:06 pm |
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| asmallri wrote: | | karsia wrote: | 18f4520 can detect 2volt even from the ttl buffer if suplly range is between 4.5 and 5.5 . You can check it from datasheet ( DC CHARACTERISTICS input low voltage- input high voltage-page 335 ).
probably most of pics can detect this. |
When configured as an SPI mode, the pin is operated in Schmitt input mode not TTL mode. |
Yes you are right. I thought for SD-1 bit or SD-4 bit mode. |
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