fatopen function with SD card writing

[martind1983]

Hi everybody.

I have question. I want to make data logger. The device should write data to SD card memory(in text form). I already found out every thing about SD card communication and I also found out, that I cannot write any data directly to root directory because there are not readable in OS (windows)
So I formated card in PC and created simple text file.
My question sounds. Can I open this text file on SD card (created in PC) by using function fatopen(char fname[], char mode[], FILE* stream)), when I lead parameter "char fname[]" as the name of my text file?
For example . First off I create variable "char FileName[] = "text.txt" and then I use it in fatopen function. Because when I try to build it, there is always error, that "a numeric expression must appear here" or "Attempt to create a pointer to a constant". I use mmcsd.c and fat.c libraries everything is included well and Before using faopen I also use fat_init function, but the result is the same. Do I have to first create file in my PIC (24F16KA102) by using function mk_file() or can I directly open the text file in my SD (creted in PC) by using function fat_open()?

Thank you very much for your help. Martin

[Ttelmah]

fatopen, does work, and do what you want.
I'd guess the problem might be the mode string, rather than the filename.
If you are using (say):

fatopen(FileName,"r",file);

then the problem is the "r", which is a constant string and can't be accepted.

Add the line

#device PASS_STRINGS=IN_RAM

up at the top of your code immediately after the processor include line.

Best Wishes

[martind1983]

Thanks for hint.
I already found it before. But there was one different problem. I didn't notice, that compiler put g_mmcsd_buffer variable to reserve range of debbuger memory, but I solved this issue too.

Thanks again. Martin

[martind1983]

Hi Ttelmah.

I already tried to do all the changes you adviced me. Compiling was goog, compiler buit and linked program.
But fatopen() function always returns EOF value. I didn't understand your reply very well so I am asking you again. Can I open file (for example test. txt) which was created in windows after formatting SD card in windows directly from SD card using by fatopen() function or do I have to make new file in PIC MCU with the same name to be able open it by function fatopen().
Next I seem that the function fat_init is buggy too. First when I lead it before fatopen() it should load all necessary variables for FAT form, but when I debug program, I always see, that only first (sector 0) is loaded to g_mmcsd_buffer. There are some information, but I am not sure, that there are FAT table statements. Neither statements(like bytes per sector, sectors, root directory, sectors per cluster...) loaded to FILE variable doesn't seem to be good. I would just like to read file directly from SD card (without creating it in PIC MCU memory) to the stream by means of function fatopen();

Thanks for your help