Open() - SPI BSP

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Last updated: Feb 04, 2014
1 min read

CPU_BOOLEAN FSDev_BSP_SPI_Open (FS_QTY unit_nbr);

File

Called from

Code enabled by

fs_dev_<dev_name>_bsp.c

Device driver

N/A

Open (initialize) hardware for SPI.

Arguments

unit_nbr

Unit number of device.

Returned Value

DEF_OK, if interface was opened.

DEF_FAIL, otherwise.

Notes/Warnings

  1. This function will be called every time the device is opened.
  2. Several aspects of SPI communication may need to be configured, including:
    • Transfer unit length
    • Shift direction
    • Clock frequency
    • Clock polarity and phase (CPOL and CPHA)
    • Slave select polarity
  3. For a SD/MMC card, the following settings should be used:
    • Transfer unit length: 8-bits
    • Shift direction: MSB first
    • Clock frequency: 400-kHz (initially)
    • Clock polarity and phase (CPOL and CPHA): CPOL = 0, CPHA = 0
    • Slave select polarity: active low.
  4. The slave select (SSEL or CS) must be configured as a GPIO output; it should not be controlled by the CPU’s SPI peripheral. The SPI port’s ChipSelEn() and ChipSelDis() functions manually enable and disable the SSEL.