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asmallri
Joined: 12 Aug 2004
Posts: 1635
Location: Perth, Australia
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 Posted: Sat Feb 24, 2018 11:37 am |
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| salih260 wrote: | thank you very much Ttelmah and temtronic..
Does the SD card draw much current? If so, it means 100% hardware problem. Because SD card + Pic + etc. It is fed from 3v3 regulator.
(Regulator max. output current is 1A.) |
I have read through the thread and have some comments
1. My drivers (Brush Electronics) come in two versions, one for the PCH compiler (PIC18 - 8 bit) and one for PCD (PIC24/dsPIC33 - 16 bit). The reason I have two different drivers is because when using 16 bit processors the data structures are WORD aligned as opposed to BYTE aligned. In theory, you could use the 16 bit driver with an 8 bit processor (I don't recommend it) however it would be wasteful of resources and performance on the 8 bit processor.
2. SD cards contain an embedded processor. A glitch on the card's power line can reset the card's processor. Power supply filtering and decoupling as close as practical to the SD card will prevent the high current transients required during write operations to the card being the cause of card related transients resetting the card. You need to use low ESR capacitors, I use 10uF and 0.1uF ceramic capacitors for new designs. Previously I used 22uF tantalum and 0.1uF ceramic capacitors for this role.
3. If you accidentally power the SD card from 5 volts or apply +5V to any of its pins, even momentarily, throw the card away. You are wasting you time working further with the card even when it appears to be still working ok.
4. Watch out for fake or low quality copy cards out of Asia. They may or may not work depending on the day of the week, whether there are clouds in the sky, if they are facing north etc.
5. During the development process ALWAYS format the card initially with a reliable SD formatter application. Do NOT rely on the windows format utility. Go to www.sdcard.org and download their free format utility.
6. The pull-up resistor on DO from the card (aka MISO) is very important. Lots of people make the mistake of "optimizing" the design by leaving it off and then you end up with the situation it works with some cards out of a batch and not others or it works on humid days but not dry days.
7. The cards should work well for SPI speeds of 10MHz and below without issue. For higher speeds, care must be taken with the layout of the tracks on the PCB as excessive capacitance can cause signal degradation.
_________________
Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!
Last edited by asmallri on Sat Feb 24, 2018 12:18 pm; edited 1 time in total |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19535
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| Posted: Sat Feb 24, 2018 12:16 pm |
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I'd add two more things.
With the code as posted in the PetitFat example, he must have:
| Code: |
#device CONST=READ_ONLY
#device PASS_STRINGS=IN_RAM
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This is because is the assumptions PetitFat makes, so doesn't apply to your drivers....
Then the user has to supply the read/write and initialise functions. He might want to post what he is actually doing for these, and particularly the clock switching. |
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salih260
Joined: 19 Feb 2018
Posts: 23
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| Posted: Mon Feb 26, 2018 3:01 am |
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Thanks asmallri.
I will make your gestures step by step. |
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salih260
Joined: 19 Feb 2018
Posts: 23
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| Posted: Mon Feb 26, 2018 3:02 am |
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Thanks Ttelmah.
I will add these. Let's see what happens this time.
good works. |
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