SPI

Enumerations
enum	spi_slave { SSB2 , SSB3 , SSE2 }
	Identifiers for available SPI slave devices. More...

Functions
int	spi_init (void)
	Initialize SPI in master mode.
int	spi_ready (void)
	Check if the SPI subsystem is initialized.
int	spi_send_n (enum spi_slave *slave, unsigned char *data, int length)
	Send a sequence of bytes to a slave without reading response.
int	spi_send (enum spi_slave *slave, unsigned char data)
	Send a single byte to a slave.
int	spi_recieve (enum spi_slave *slave, unsigned char *out)
	Receive one byte from a slave.
int	spi_recieve_n (enum spi_slave *slave, unsigned char *out, int length)
	Receive several bytes from a slave.
int	spi_duplex (enum spi_slave *slave, unsigned char *data, unsigned char *out, int length)
	Full-duplex SPI transfer.
int	spi_set_slave_select (enum spi_slave *slave, unsigned char state)
	Set the slave-select line for the given device.
int	spi_push (enum spi_slave *slave, unsigned char data, unsigned char *out)
	Push one byte to a slave and optionally read the response.

Detailed Description

Enumeration Type Documentation

spi_slave

enum spi_slave

#include <spi.h>

Identifiers for available SPI slave devices.

Enumerator
SSB2	Slave on PB2
SSB3	Slave on PB3
SSE2	Slave on PE2

Definition at line 15 of file spi.h.

               {
  SSB2, 
  SSB3, 
  SSE2  
};

Function Documentation

spi_duplex()

int spi_duplex	(	enum spi_slave *	slave,
		unsigned char *	data,
		unsigned char *	out,
		int	length )

#include <spi.h>

Full-duplex SPI transfer.

Sends length bytes and reads a response simultaneously.

Parameters

[in]	slave	Pointer to slave device.
[in]	data	Transmit buffer, or TRASHCAN for dummy writes.
[out]	out	Receive buffer, or TRASHCAN to discard input.
[in]	length	Number of bytes to exchange.

Returns

0 on success.

Definition at line 131 of file spi.c.

                           {
  spi_set_slave_select(slave, 0);
 
  for (int i = 0; i < length; i++) {
    unsigned char tx = 0xFF;
    if (data != TRASHCAN) {
      tx = data[i];
    }
 
    SPDR = tx;
    while (!(SPSR & (1 << SPIF))) {
    }
 
    if (out != TRASHCAN) {
      out[i] = SPDR;
    }
  }
 
  spi_set_slave_select(slave, 1);
  return 0;
}

Referenced by MCP2515_bit_modify(), MCP2515_read(), MCP2515_read_status(), spi_recieve(), spi_recieve_n(), spi_send(), and spi_send_n().

spi_init()

int spi_init

(

void

)

#include <spi.h>

Initialize SPI in master mode.

Configures MOSI, SCK, and SS pins, sets clock prescaler, and ensures all slave-select lines default to inactive.

Returns

0 on success, non-zero on failure.

Definition at line 9 of file spi.c.

               {
  int status = 0;
 
  DDRB |= (1 << PB5) | (1 << PB7) |
          (1 << PB4); // Sets the required PORT B pins to SPI mode
 
  SPCR |= (1 << SPE) |
          (1 << MSTR)    // Enables the SPI-bus and sets it to master mode, MSB
          | (1 << SPR0); // first, no interrupt, and a clock freq of f_osc/4
 
  /*
  // Define PB2, PB4 and PE2 as slave select pins
  */
  DDRB |= (1 << PB2) | (1 << PB3) | (1 << PB4);
  DDRE |= (1 << PE2);
 
  /*
  // Ensure initial state off
  */
  status = spi_set_slave_select((enum spi_slave *)SSB2, 1);
  status = spi_set_slave_select((enum spi_slave *)SSB3, 1);
  status = spi_set_slave_select((enum spi_slave *)SSE2, 1);
 
  if (status) {
    return status;
  }
 
  _ready = 1;
 
  return status;
}

Referenced by io_avr_init(), io_oled_init(), and MCP2515_init().

spi_push()

int spi_push	(	enum spi_slave *	slave,
		unsigned char	data,
		unsigned char *	out )

#include <spi.h>

Push one byte to a slave and optionally read the response.

Parameters

[in]	slave	Pointer to target slave.
[in]	data	Byte to send.
[out]	out	Pointer to received byte (or TRASHCAN to ignore).

Returns

0 on success.

Definition at line 154 of file spi.c.

                                                                            {
 
  spi_set_slave_select(slave, 0);
  SPDR = data;
  while (!(SPSR & (1 << SPIF))) {
  }
 
  // Only write if pointer is valid
  if (out != TRASHCAN) {
    *out = SPDR;
  }
  return 0;
}

Referenced by io_avr_buttons_read().

spi_ready()

int spi_ready

(

void

)

#include <spi.h>

Check if the SPI subsystem is initialized.

Returns

0 if ready, non-zero otherwise.

Definition at line 41 of file spi.c.

{ return !_ready; }

Referenced by io_avr_init(), io_oled_init(), and MCP2515_init().

spi_recieve()

int spi_recieve	(	enum spi_slave *	slave,
		unsigned char *	out )

#include <spi.h>

Receive one byte from a slave.

Transmits dummy data and stores the received byte.

Parameters

[in]	slave	Pointer to target slave.
[out]	out	Pointer to received byte.

Returns

0 on success.

Definition at line 91 of file spi.c.

                                                           {
  spi_duplex(slave, TRASHCAN, out, 1);
  return 0;
}

spi_recieve_n()

int spi_recieve_n	(	enum spi_slave *	slave,
		unsigned char *	out,
		int	length )

#include <spi.h>

Receive several bytes from a slave.

Parameters

[in]	slave	Pointer to target slave.
[out]	out	Buffer to store received data.
[in]	length	Number of bytes to read.

Returns

0 on success.

Definition at line 96 of file spi.c.

                                                                         {
  spi_duplex(slave, TRASHCAN, out, length);
  return 0;
}

Referenced by io_avr_buttons_read().

spi_send()

int spi_send	(	enum spi_slave *	slave,
		unsigned char	data )

#include <spi.h>

Send a single byte to a slave.

Parameters

[in]	slave	Pointer to target slave.
[in]	data	Byte to transmit.

Returns

0 on success.

Definition at line 86 of file spi.c.

                                                        {
  spi_duplex(slave, &data, TRASHCAN, 1);
  return 0;
}

Referenced by _io_oled_cmd(), _io_oled_write(), MCP2515_request_to_send(), and MCP2515_reset().

spi_send_n()

int spi_send_n	(	enum spi_slave *	slave,
		unsigned char *	data,
		int	length )

#include <spi.h>

Send a sequence of bytes to a slave without reading response.

Parameters

[in]	slave	Pointer to the target slave device.
[in]	data	Buffer of bytes to transmit.
[in]	length	Number of bytes to send.

Returns

0 on success.

Definition at line 81 of file spi.c.

                                                                       {
  spi_duplex(slave, data, TRASHCAN, length);
  return 0;
}

Referenced by io_avr_led_set(), MCP2515_init(), MCP2515_write(), and MCP2515_write_n().

spi_set_slave_select()

int spi_set_slave_select	(	enum spi_slave *	slave,
		unsigned char	state )

#include <spi.h>

Set the slave-select line for the given device.

Parameters

[in]	slave	Pointer to slave identifier.
[in]	state	0 = select (active), 1 = deselect.

Returns

0 on success, -1 if slave is invalid.

Definition at line 43 of file spi.c.

                                                                     {
  switch (*slave) {
  case SSB2:
    if (!state) {
      PORTB |= (1 << PB3);
      PORTE |= (1 << PE2);
 
      PORTB &= ~(1 << PB2);
    } else {
      PORTB |= (1 << PB2);
    }
    break;
  case SSE2:
    if (!state) {
      PORTB |= (1 << PB2);
      PORTB |= (1 << PB3);
 
      PORTE &= ~(1 << PE2);
    } else {
      PORTE |= (1 << PE2);
    }
    break;
  case SSB3:
    if (!state) {
      PORTB |= (1 << PB2);
      PORTE |= (1 << PE2);
 
      PORTB &= ~(1 << PB3);
    } else {
      PORTB |= (1 << PB3);
    }
    break;
  default:
    return -1;
  }
  return 0;
}

Referenced by io_avr_buttons_read(), spi_duplex(), spi_init(), and spi_push().