Class: SPI::LinuxSPIdev

Inherits:
Object
  • Object
show all
Defined in:
lib/mruby/spi.rb

Overview

Linux SPI Device driver

Constant Summary collapse

IOC_NONE =

Constants see: /usr/include/linux/spi/spidev.h, /usr/include/asm-generic/ioctl.h

0
IOC_WRITE = 
1
IOC_READ = 
2
SPI_IOC_MAGIC = 
'k'.ord
SPI_IOC_RD_MODE =

Read / Write of SPI mode (SPI_MODE_0..SPI_MODE_3) (limited to 8 bits) define SPI_IOC_RD_MODE _IOR(SPI_IOC_MAGIC, 1, __u8) define SPI_IOC_WR_MODE _IOW(SPI_IOC_MAGIC, 1, __u8)

_IOx( type, nr, size ) is bit mapped [RW][size:14][type:8][nr:8]
                        dir             | size    | type               | nr

IOC_READ  << 30 | 1 << 16 | SPI_IOC_MAGIC << 8 | 1
SPI_IOC_WR_MODE = 
IOC_WRITE << 30 | 1 << 16 | SPI_IOC_MAGIC << 8 | 1
SPI_IOC_RD_LSB_FIRST =

Read / Write SPI bit justification define SPI_IOC_RD_LSB_FIRST _IOR(SPI_IOC_MAGIC, 2, __u8) define SPI_IOC_WR_LSB_FIRST _IOW(SPI_IOC_MAGIC, 2, __u8)

dir             | size    | type               | nr

IOC_READ  << 30 | 1 << 16 | SPI_IOC_MAGIC << 8 | 2
SPI_IOC_WR_LSB_FIRST = 
IOC_WRITE << 30 | 1 << 16 | SPI_IOC_MAGIC << 8 | 2
SPI_IOC_RD_BITS_PER_WORD =

Read / Write SPI device word length (1..N) define SPI_IOC_RD_BITS_PER_WORD _IOR(SPI_IOC_MAGIC, 3, __u8) define SPI_IOC_WR_BITS_PER_WORD _IOW(SPI_IOC_MAGIC, 3, __u8)

dir             | size    | type               | nr

IOC_READ  << 30 | 1 << 16 | SPI_IOC_MAGIC << 8 | 3
SPI_IOC_WR_BITS_PER_WORD = 
IOC_WRITE << 30 | 1 << 16 | SPI_IOC_MAGIC << 8 | 3
SPI_IOC_RD_MAX_SPEED_HZ =

Read / Write SPI device default max speed hz define SPI_IOC_RD_MAX_SPEED_HZ _IOR(SPI_IOC_MAGIC, 4, __u32) define SPI_IOC_WR_MAX_SPEED_HZ _IOW(SPI_IOC_MAGIC, 4, __u32)

dir             | size    | type               | nr

IOC_READ  << 30 | 4 << 16 | SPI_IOC_MAGIC << 8 | 4
SPI_IOC_WR_MAX_SPEED_HZ = 
IOC_WRITE << 30 | 4 << 16 | SPI_IOC_MAGIC << 8 | 4
SPI_IOC_MESSAGE =

define SPI_IOC_MESSAGE(N) _IOW(SPI_IOC_MAGIC, 0, char)

char[SPI_MSGSIZE(1) is 32 bytes.
NOTE: struct layout is the same in 64bit and 32bit userspace.
                        dir             | size    | type               | nr

IOC_WRITE << 30 |32 << 16 | SPI_IOC_MAGIC << 8 | 0

Instance Method Summary collapse

Constructor Details

#initialize(node, frequency, mode, first_bit) ⇒ LinuxSPIdev

constructor

Parameters:

  • node (String) —

    device node of SPI

  • frequency (Integer) —

    SCLK frequency.

  • mode (Integer) —

    SPI mode (0..3)

  • first_bit (Constant) —

    MSB_FIRST or LSB_FIRST

See Also:



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# File 'lib/mruby/spi.rb', line 91

def initialize(node, frequency, mode, first_bit)
  @device = File.open(node, "r+:ASCII-8BIT")

  _set_max_speed_hz( frequency )
  _set_mode( mode )
  _set_lsb_first( first_bit )
end

Instance Method Details

#read(read_bytes) ⇒ String

Reads data of read_bytes bytes from the SPI bus.

Parameters:

  • read_bytes (Integer) —

    read bytes.

Returns:

  • (String) —

    reading datas.



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# File 'lib/mruby/spi.rb', line 119

def read( read_bytes )
  @device.sysread( read_bytes )
end

#setmode(frequency: nil, mode: nil) ⇒ void

This method returns an undefined value.

Changes the operating mode (parameters) of the SPI.

Parameters:

  • frequency (Integer) (defaults to: nil) —

    SCLK frequency.

  • mode (Integer) (defaults to: nil) —

    SPI mode (0..3)



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# File 'lib/mruby/spi.rb', line 107

def setmode( frequency:nil, mode:nil )
  _set_max_speed_hz( frequency )  if frequency
  _set_mode( mode )  if mode
end

#transfer(outputs, additional_read_bytes = 0) ⇒ String

Outputs data specified in outputs to the SPI bus while simultaneously reading data (General-purpose transfer).

Parameters:

  • outputs (Integer, String, Array<Integer>) —

    output data.

  • additional_read_bytes (Integer) (defaults to: 0) —

    additional read bytes

Returns:

  • (String) —

    reading datas.



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# File 'lib/mruby/spi.rb', line 145

def transfer( outputs, additional_read_bytes = 0 )

  # prepare the send buffer and receive buffer.
  send_data = _rebuild_output_data( [outputs] )
  len = send_data.size
  if additional_read_bytes > 0
    send_data << ("\x00".b * additional_read_bytes)
    len += additional_read_bytes
  end
  recv_data = "\x00".b * len

  # prepare the struct spi_ioc_transfer. (spidev.h)
  arg = [ [send_data].pack("P").unpack1("J"), # __u64           tx_buf;
          [recv_data].pack("P").unpack1("J"), # __u64           rx_buf;

          len,        # __u32           len;
          0,          # __u32           speed_hz;

          0,          # __u16           delay_usecs;
          0,          # __u8            bits_per_word;
          0,          # __u8            cs_change;
          0,          # __u8            tx_nbits;
          0,          # __u8            rx_nbits;
          0,          # __u8            word_delay_usecs;
          0,          # __u8            pad;
        ].pack("QQLLSCCCCCC")

  # trigger IOCTL.
  @device.ioctl( SPI_IOC_MESSAGE, arg )
  return recv_data
end

#write(*outputs) ⇒ nil

Outputs data specified in outputs to the SPI bus.

Parameters:

  • outputs (Integer, String, Array<Integer>) —

    output data.

Returns:

  • (nil) 


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# File 'lib/mruby/spi.rb', line 130

def write( *outputs )
  send_data = _rebuild_output_data( outputs )
  @device.syswrite( send_data )
  return nil
end