SPI Interface

Note

SPI is a fast serial interface made for talking to sensors, ICs and other peripherals. The Seeed and Pmod connectors allow for additional SPI modules to be connected.

Simple Usage

Reading from and writing to a SPI device is as simple as calling the read and write functions of the relevant SPI interface. For example, for a device connected to the PMOD A connector, the following code can be used to read data:

CC++

u32 rxdata = 0;

// Read an u32
yggdrasil_SPI_Read(SPIC, &rxdata, sizeof(u32));


u8 rxarray[10] = { 0 };

// Read an array of 10 u8
yggdrasil_SPI_Read(SPIC, rxarray, sizeof(rxarray));

And this code to write data:

CC++

u32 txdata = 0x12345678;

// Write an u32
yggdrasil_SPI_Write(SPIC, &txdata, sizeof(u32));

u8 txarray[5] = { 1, 2, 3, 4, 5 };

// Write an array of 5 u8
yggdrasil_SPI_Read(SPIC, txarray, sizeof(txarray));

Important

All SPI interfaces are configured in Full-Duplex Master, MSB First, Mode 3 with a data rate of 6.75 MBits/s. If other settings are needed, they can be changed in the project’s .ioc file.

Available peripherals

Peripheral	Bus	Chip Enable
RGB LED Matrix	SPIA	RGB_EN
Pressure Sensor	SPIA	Hardware NSS
PMOD A	SPIC	Hardware NSS
Raspberry Port	SPIB	SPIBCE
Raspberry Port	SPIC	Hardware NSS

Custom SPI

In order to control a SPI that has not been pre-defined by libyggdrasil, first it needs to be properly configured through the project’s .ioc file. Once this is done, the new SPI can be defined like this:

CC++

spi_t MySPI = { &hspi1 };

and then used like all the other SPI.