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Using the SD card on the Wunderboard

Using the SD card on the Wunderboard. ECE152. Overview. What is a file system? How can I open files? How do I read and write from files? What about 'error codes'? Coding example. What is a file system?. Memory is just a long list of locations File systems organize memory

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Using the SD card on the Wunderboard

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  1. Using the SD card on the Wunderboard ECE152

  2. Overview • What is a file system? • How can I open files? • How do I read and write from files? • What about 'error codes'? • Coding example

  3. What is a file system? • Memory is just a long list of locations • File systems organize memory • File systems are created based on the memory uint8_t initializeFAT(FATFS* fs)

  4. How can I open files? • Files are opened for reading or writing • Files can be created, overwritten, or appended to f_open(&log, "/log.txt", FA_WRITE | FA_CREATE_ALWAYS)

  5. How do I write to files? • You write data as bytes • When writing, tell the function how many bytes • f_write (FIL*, const void*, UINT, UINT*) • FIL - File 'handle' • const void* - data to be written • UINT - number of bytes to write • UINT* - number of bytes written

  6. What about 'error codes'? switch (err) { case ERR_FMOUNT: sendStringUART("ERROR: Could not mount SD\r\n"); break; case ERR_NODISK: sendStringUART("ERROR: No SDC/MMC present\r\n"); break; case ERR_NOINIT: sendStringUART("ERROR: Unable to initialize FAT.\r\n"); break; ...etc...

  7. Coding example

  8. Things to Remember • Always double check the error codes • When in doubt, ask questions.

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