라즈베리파이 : SPI ( Speed etc.)

Speed

The driver supports the following speeds:

  cdiv    speed
     2    125.0 MHz
     4     62.5 MHz
     8     31.2 MHz
    16     15.6 MHz
    32      7.8 MHz
    64      3.9 MHz
   128     1953 kHz
   256      976 kHz
   512      488 kHz
  1024      244 kHz
  2048      122 kHz
  4096       61 kHz
  8192     30.5 kHz
 16384     15.2 kHz
 32768     7629 Hz

When asking for say 24 MHz, the actual speed will be 15.6 MHz.

Forum post: SPI has more speeds

Supported Mode bits

SPI_CPOL    - Clock polarity
SPI_CPHA    - Clock phase
SPI_CS_HIGH - Chip Select active high
SPI_NO_CS   - 1 device per bus, no Chip Select
SPI_3WIRE   - Bidirectional mode, data in and out pin shared

Bidirectional or "3-wire" mode is supported by the spi-bcm2835 kernel module. Please note that in this mode, either the tx or rx field of the spi_transfer struct must be a NULL pointer, since only half-duplex communication is possible. Otherwise, the transfer will fail. The spidev_test.c source code does not consider this correctly, and therefore does not work at all in 3-wire mode.

Supported bits per word

• 8 - Normal
• 9 - This is supported using LoSSI mode.

Transfer modes

Only interrupt mode is supported.