Summary of ulibSD – a library for use SD cards in SPI mode with uControllers
ulibSD is a C library enabling SD card interaction in SPI mode with microcontrollers. It supports 512-byte data transfers and includes PC file emulation for debugging on GNU/Linux. The project relies on hardware-specific implementations for SPI operations and integer type definitions to ensure portability across different platforms.
Parts used in ulibSD:
- SD Card
- Microcontroller (uController)
- spi_io.h header
- integer.h file
- spi_io.c.example file
- KL25Z board
- OpenKL25Z framework
ulibSD
It’s a library for use SD cards in SPI mode with uControllers, entirely writtenin C. This library can work with SD cards and also has the possibility to emulate the behavior in a PC file (GNU/Linux) using the macro _M_IX86. It’s for debugging purposes. The data transfer is oriented to 512 byte size,
remember this.
Public methods
ulibSD has four public methods:
- SD_Init: Initialization the SD card.
- SD_Read: Read a single block of data.
- SD_Write: Write a single block of data.
- SD_Status: Allows know status of SD card.
Those methods require a device descriptor.
How is possible port the code to my platform?
This library uses a spi_io.h header. Here are defined the low-level methods
associated with the hardware. Those methods are:
SPI_Init: Initialize SPI hardware.SPI_RW: Read/Write a single byte. Returns the byte that arrived.SPI_Release: Flush of SPI buffer.SPI_CS_Low: Selecting function in SPI terms, associated with SPI module.SPI_CS_High: Deselecting function in SPI terms, associated with SPI module.SPI_Freq_High: Setting frequency of SPI’s clock to maximun possible.SPI_Freq_Low: Setting frequency of SPI’s clock equal or lower than 400kHz.SPI_Timer_On: Start a non-blocking timer in milliseconds.SPI_Timer_Status: Check the status of non-blocking timer.SPI_Timer_Off: Stop of non-blocking timer.
You need write the proper code for this methods. I leave a spi_io.c.example
file for use as guideline. I hope this helps to you understand how is the logic
of portability. This example is for KL25Z board using my OpenKL25Z framework.
Also you need verify and adapt the integer types in the integer.h file.
Read more: ulibSD – a library for use SD cards in SPI mode with uControllers
- How does ulibSD handle data transfer sizes?
The data transfer is oriented to 512 byte size. - Can ulibSD work without an actual SD card?
Yes, it can emulate behavior in a PC file using the macro _M_IX86 for debugging. - What are the four public methods provided by ulibSD?
They are SD_Init, SD_Read, SD_Write, and SD_Status. - Does every method require a device descriptor?
Yes, all those methods require a device descriptor. - Which header defines the low-level hardware methods?
The spi_io.h header defines the low-level methods associated with the hardware. - How do I set the SPI clock frequency to maximum?
You use the SPI_Freq_High function to set the frequency to the maximum possible. - What frequency limit applies when setting SPI clock to low?
The frequency must be equal or lower than 400kHz. - Is there an example file provided for porting logic?
Yes, a spi_io.c.example file is provided as a guideline for the KL25Z board.
