HardwareSPI

This class is used for creating objects to manage the Maple’s built-in SPI ports. The Maple has two SPI ports. The relevant pins corresponding to each port’s logic signals are documented in the following table (and on the Maple silkscreen):

Port number	NSS	MOSI	MISO	SCK
1	10	11	12	13
2	31	32	33	34

If you use a SPI port, you cannot simultaneously use its associated pins for other purposes.

Library Documentation

Using the SPI Class

You can declare that you want to use SPI in your sketch by putting HardwareSPI Spi(number); with your variables, where number is 1 or 2, depending on which SPI you want to use. Then you can use the functions described in the next section. For example:

// Use SPI 1
HardwareSpi Spi(1);

void setup() {
    Spi.begin(SPI_18MHZ);
}

void loop() {
    // Get the next byte from the peripheral
    uint8 byte = Spi.recv();
}

HardwareSPI Class Reference

class HardwareSPI

Class for interacting with SPI.

HardwareSPI::HardwareSPI(uint32 spi_num)

Construct an object for managing a SPI peripheral. spi_num must be 1 or 2; see the table above for pinout information.

void HardwareSPI::begin(SPIFrequency freq, uint32 endianness, uint32 mode)

Configure the baudrate of the given SPI port and set up the header pins appropriately.

Parameters:

• freq: one of the SPIFrequency values, given below.

• endianness: either LSBFIRST (little-endian) or MSBFIRST (big-endian).

• mode: one of 0, 1, 2, or 3, and specifies which SPI mode is used. The mode number determines a combination of polarity and phase according to the following table:

  Mode	Polarity	Phase
  0	0	0
  1	0	1
  2	1	0
  3	1	1

  For more information on polarity and phase, see the external references, below.

void HardwareSPI::begin()

A convenience begin(), equivalent to begin(SPI_1_125MHZ, MSBFIRST, 0).

uint8 HardwareSpi::send(uint8* data, uint32 length)

Writes data into the port buffer to be transmitted as soon as possible, where length is the number of bytes to send from data. Returns the last byte shifted back from slave.

uint8 HardwareSpi::send(uint8 data)

Writes the single byte data into the port buffer to be transmitted as soon as possible. Returns the data byte shifted back from the slave.

uint8 HardwareSpi::recv()

Reads a byte from the peripheral. Returns the next byte in the buffer.

SPI Speeds

The possible SPI speeds are configured using the SPIFrequency enum:

SPIFrequency enum

HardwareSPI definitions.

Defines the possible SPI communication speeds.

Values:

• SPI_18MHZ = 0 -

  18 MHz

• SPI_9MHZ = 1 -

  9 MHz

• SPI_4_5MHZ = 2 -

  4.5 MHz

• SPI_2_25MHZ = 3 -

  2.25 MHZ

• SPI_1_125MHZ = 4 -

  1.125 MHz

• SPI_562_500KHZ = 5 -

  562.500 KHz

• SPI_281_250KHZ = 6 -

  281.250 KHz

• SPI_140_625KHZ = 7 -

  140.625 KHz

• MAX_SPI_FREQS = 8 -

  The number of SPI frequencies.

See Also

• Wikipedia Article on Serial Peripheral Interface Bus (SPI)
• Arduino reference on SPI
• Hardcore SPI on Arduino by kik64
• STMicro documentation for STM32F103RB microcontroller:
  • Datasheet (pdf)
  • Reference Manual (pdf)