MicroSD Cards and SDFS

[mackrackit]

Unfortunately it looks like you need a chip with more memory to do both.

Any way you could use two MCUs and have them share data? Not the best solution but... it is all I can think of off the top.

[rsocor01]

Unfortunately it looks like you need a chip with more memory to do both.

Any way you could use two MCUs and have them share data? Not the best solution but... it is all I can think of off the top.

Hmmm, I problably didn't explain myself very clear . I get this SDC_buffer error running SDFS only with the file 18F4550.bal in the same directory. This file is necessary to run USB with PBPL. I haven't tried both USB and SDFS at the same time yet. I will probably open a new thread on this problem.

Robert

[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