MicroSD Cards and SDFS

[mackrackit]

If you do not need the USB function of the chip then remove the bal file.
I am pretty sure PBP will include it if it is in the project directory even if you are not using it. IT being bal

[rsocor01]

mackrackit,

My project is going well. Without your help I would be still stuck trying to make this SDFS work. Thank you for your help.

After a lot of reading, I figured out a way to make USB and SDFS work. I had to modify the 18F4550.bal file. There are two versions of this file, one for USB and one for non-USB devices. The option for USB devices had some memory settings commented out. I enabled back these settings and BINGO, it worked.

Robert

[rsocor01]

mackrackit,

In my project, data is read from the MicroSD card and sent to a TFT LCD display. As you can imagine, speed is very important. Let's say that I have the following bytes in my TXT file and I want to read them

203
37
92

When you read these values with SDFS you get something like

FAT_dest[0] = 50     'ASCII number for "2"
FAT_dest[1] = 48     'ASCII number for "0"
FAT_dest[2] = 51     'ASCII number for "3"
FAT_dest[3] = 13     'ASCII number for "CR"
FAT_dest[4] = 10     'ASCII number for "LF"
FAT_dest[5] = 51     'ASCII number for "3"
FAT_dest[6] = 55     'ASCII number for "7"
FAT_dest[7] = 13     'ASCII number for "CR"
FAT_dest[8] = 10     'ASCII number for "LF"
FAT_dest[9] = 57     'ASCII number for "9"
FAT_dest[10] = 50     'ASCII number for "2"

Then, you have to do some data manipulation to obtain the bytes that you need, 203, 37, and 92. This takes too much time . Is there any way or is there any format for my TXT file that I can use were I would obtain a SDFS reading like the following?

FAT_dest[0] = 203  
FAT_dest[1] = 37
FAT_dest[2] = 92

This would speed up my program a lot and I would obtain much better graphics in my TFT display. Thank you for your help.

Robert

[mackrackit]

I do not have a good answer at the moment. I mostly use SD card for logging and yes the FAT file system can be a bit slow.

How often is the display updated in your app?

[rsocor01]

........ and yes the FAT file system can be a bit slow.

So, is the FAT32 (SDFSHC32) much faster than FAT (SDFS3)? I didn't go for the FAT32 because it takes a lot of space in the chip.

The display changes whenever a new screen is selected and hopefully the transition should be smooth. What do you think would be the best way to read the data from the card the way I need it?

Robert

[mackrackit]

Can not say exactly but FAT32 should be a little slower, larger sectors to read I guess.

Can you have the data on the card in CSV format instead of line by line? Be a little less reading.

Might post your code, maybe someone will see something?

[rsocor01]

Can not say exactly but FAT32 should be a little slower, larger sectors to read I guess.

Good guess! I did some research in google and FAT32 is slower than FAT. I think that I found a solution to the problem I'm having, but I have to test it before I post it here.

My code is just the SDFS code, the EasyHID code, and the code to drive the TFT display all mixed together. I'm just testing everything together and so far my program is working fine.

Robert