The following is an example program that simulates an SPI (Serial Peripheral Interface) bus controller using the C language, implementing the functionality of SPI through simulated GPIO pin operations, including initialization, sending bytes, and receiving bytes. This example is suitable for general microcontroller platforms, and the GPIO operation code needs to be modified according to the specific hardware platform in practical applications.
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#include <stdint.h> #include <stdbool.h> // Assuming this is the macro definition for GPIO pin operations, it needs to be modified according to the specific hardware platform in actual use. #define SPI_SCK_PIN 1 // Clock pin number #define SPI_MOSI_PIN 2 // Master Out Slave In pin number #define SPI_MISO_PIN 3 // Master In Slave Out pin number #define SPI_CS_PIN 4 // Chip Select pin number #define SET_SCK() // This should implement the code to set the SCK pin to high, for example, operations on specific GPIO registers. #define CLEAR_SCK() // This should implement the code to set the SCK pin to low. #define SET_MOSI() // This should implement the code to set the MOSI pin to high. #define CLEAR_MOSI() // This should implement the code to set the MOSI pin to low. #define READ_MISO() // This should implement the code to read the level of the MISO pin, returning a value of 0 or 1 #define SET_CS() // This should implement the code to set the CS pin to high. #define CLEAR_CS() // This should implement the code to set the CS pin to low. // Simulated SPI delay function, adjust according to actual conditions. void spi_delay(void) { // Simple empty loop delay, adjust the loop count according to hardware speed. for (int i = 0; i < 100; i++); } // SPI initialization function void spi_init(void) { // Set the SCK, MOSI, CS pins to output mode, and the MISO pin to input mode. // This should implement the specific GPIO mode setting code. SET_SCK(); SET_MOSI(); SET_CS(); spi_delay(); } // Send a byte of data void spi_send_byte(uint8_t byte) { for (int i = 7; i >= 0; i–) { if (byte & (1 << i)) { SET_MOSI(); } else { CLEAR_MOSI(); } SET_SCK(); spi_delay(); CLEAR_SCK(); spi_delay(); } } // Receive a byte of data uint8_t spi_receive_byte(void) { uint8_t received_byte = 0; for (int i = 7; i >= 0; i–) { SET_SCK(); spi_delay(); if (READ_MISO()) { received_byte |= (1 << i); } CLEAR_SCK(); spi_delay(); } return received_byte; } // Perform an SPI data transfer (send and receive) void spi_transfer(uint8_t send_data, uint8_t *receive_data) { CLEAR_CS(); spi_delay(); spi_send_byte(send_data); *receive_data = spi_receive_byte(); SET_CS(); spi_delay(); } |
You can call these functions to implement SPI communication as follows:
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int main(void) { spi_init(); uint8_t send_data = 0x55; uint8_t receive_data; spi_transfer(send_data, &receive_data); return 0; } |
The above code simulates the basic functionality of the SPI bus. In practical applications, it is necessary to accurately set the GPIO operation part according to the specific hardware platform, and further improve and expand the code according to the communication requirements with the SPI device, such as handling different SPI modes (combinations of CPOL and CPHA).