Use gpio to simulate SPI bus for communication

The pseudo code for reading and writing the analog SPI bus in Mode 1 is provided below to illustrate how to implement SPI communication using gpio:

# Define SS 252 // defines the gpio interface number corresponding to the SS # define sclk 253 // defines the gpio interface number corresponding to the sclk # define MoSi 254 // defines the gpio corresponding to the sclk interface # define miso 255 // defines the gpio interface number corresponding to miso # define outp 1 // indicates that the gpio interface direction is output # define indium 0 // indicates that the gpio interface direction is input /* SPI port initialization */void spi_init () {callback (SS, outp); set_gpio_direction (sclk, outp); set_gpio_direction (MoSi, outp); set_gpio_direction (Miso, indium); set_gpio_value (sclk, 0 ); // cpol = 0 set_gpio_value (MoSi, 0);}/* enable signal valid when enable is set to 1 from the device, when the SS low level is 0, invalid enabling signal, SS high */void ss_enable (INT enable) {If (enable) set_gpio_value (SS, 0); // SS low level, enable valid else set_gpio_value (SS, 1) from the device; // SS high level, invalid from the device}/* SPI byte write */void spi_write_byte (unsigned char B) {int I; for (I = 7; I> = 0; I --) {set_gpio_value (sclk, 0); set_gpio_value (MoSi, B & (1 <I )); // serial write delay () from the top 7 to the low 0; // set_gpio_value (sclk, 1); // cpha = 1, sample delay () ;}/ * SPI byte read */unsigned char spi_read_byte () {int I; unsigned char r = 0; for (I = 0; I <8; I ++) {set_gpio_value (sclk, 0); delay (); // set_gpio_value (sclk, 1 ); // cpha = 1, sampling r = (r <1) | get_gpio_value (Miso) in the first hop of the clock ); // serial reading delay () ;}/ * SPI write operation Buf: write buffer Len: length of the written bytes */void spi_write (unsigned char * Buf, int Len) {int I; spi_init (); // initialize the gpio interface ss_enable (1 ); // delay () starts when the device is enabled and the communication starts. // latency // write data for (I = 0; I <Len; I ++) spi_write_byte (BUF [I]); delay (); ss_enable (0); // The slave device cannot be enabled, communication ends}/* SPI read operation Buf: read buffer Len: length of the read bytes */void spi_read (unsigned char * Buf, int Len) {int I; spi_init (); // initialize the gpio interface ss_enable (1 ); // delay () starts when the device is enabled and the communication starts. // delay // read the data for (I = 0; I <Len; I ++) buf [I] = spi_read_byte (); delay (); ss_enable (0); // The enable of the slave device is invalid and the communication ends}

In the above Code, the spi_read and spi_write functions can be used to simulate SPI read/write by gpio.