SD-Card Detection Command in PROS

Programming Support PROS Support
1

I’m currently working on using the SD Card in PROS and was wondering if there is a command that returns a boolean for if the SD-Card is connected. Similar to the vex::brain::sdcard.isInserted
from the VC API. And if a function doesn’t exist a recommended way for creating my own. Thanks for any help in advance!

1069B - Argonauts

2

Looks like there is but we havent exposed it. If you file an issue on the PROS repository we can get that added to the next release. In the meantime, I think you should be able to just check the result of attempting to open the file (it’ll should be something invalid if there’s no SD card mounted)

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3

So I’m currently attempting to create my own function with the following code:

bool SDCardIsInserted(){
std::fstream m_file;
m_file.open("/usd/testFile.txt", std::ios::out);
m_file.close();

m_file.open("/usd/testFile.txt", std::ios::in);
if(m_file.is_open()){
  m_file.close();
  remove("/usd/testFile.txt"); // This is the issue 
  return true;
}
return false;
}

and when I compile the code I get this error:

Linking hot project with ./bin/cold.package.elf and libc,libm,libpros,okapilib [ERRORS]
/usr/local/Cellar/arm-gcc-bin/8-2018-q4-major/bin/../lib/gcc/arm-none-eabi/8.2.1/../../../../arm-none-eabi/bin/ld: ./firmware/libc.a(lib_a-unlinkr.o): in function `_unlink_r':
unlinkr.c:(.text._unlink_r+0x12): undefined reference to `_unlink'
collect2: error: ld returned 1 exit status

This error is due to attempting to delete the test file after detection but I can’t figure out how to solve this issue. I could solve by just not deleting the file and opening one of the permanent files but I would prefer to create a new file and then delete just in case the permanent file address/name changes. Any recommendations?

4

Yeah we don’t have _unlink defined. Why are you trying to delete the file?

5

If the SD-Card is plugged in it would create testFile.txt and then I would like to remove it. I could base the detection of a permanent file but if that file is changed(address or name) or is removed by hand the program would believe that the SD Card ins’t plugged in when it is.

6

IIRC there is no delete file available in the SDK, I didn’t want anyone accidentally deleting a whole bunch of important files.

1 Like
7

@jpearman & @hotel thanks for the input, it makes sense! Thanks you for the clarifications.

8

By the way, when I mentioned you could check the result of attempting to open a file, I had something like this in mind:

std::ifstream f("/usd/file.txt"); // open file for reading
if (!file) {
    // Failed to open for some reason, handle it
}

It appears that operator ! is overridden for the fstream family to check for the fail trait. I’d argue that you should probably be checking the success of opening a file anyway (and also it doesn’t really matter whether a file failed to open because it didn’t exist or because the SD card isn’t plugged in-- either way there’s no file).

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