You can interact with files on the microSD card (you can not interact with files on the V5 brain’s flash) through standard C/C++ file I/O methods. For the most part, you can follow along with any standard C tutorial for file I/O and it will work with PROS. Here are a couple of recommended tutorials:

The only additional detail needed for interacting with the filesystem in PROS is that any files on the microSD card must be prefaced with /usd/. A file on the microSD card can be written to in the following manner:

FILE* usd_file_write = fopen("/usd/example.txt", "w");
fputs("Example text", usd_file_write);

FILE* usd_file_read = fopen("/usd/example.txt", "r");
char buf[50]; // This just needs to be larger than the contents of the file
fread(buf, 1, 50, usd_file_read); // passing 1 because a `char` is 1 byte, and 50 b/c it's the length of buf
printf("%s\n", buf); // print the string read from the file
// Should print "Example text" to the terminal
fclose(usd_file_read); // always close files when you're done with them


The microSD card must be fat32 in order to work.


It’s also possible to interact with the serial communications (stdin, stdout, etc.) through the filesystem drivers. You can write and read from these streams in the same manner as a file, but using the four character stream identifiers.

For instance, you can write to stderr in the following manner:

FILE* stderr = fopen("serr", "w");
fputs("Example text", stderr);

There are also a number of methods for controlling serial communication behavior exposed in apix.h. These methods can be accessed through the serctl() function. At the moment two actions are supported - activating/deactivating the streams, and enabling/disabling COBS . If you want to read the serial comms yourself (without using pros terminal), then you’ll want to disable COBS.