Software FIFO Buffer for UART Communication
阿新 • • 發佈：2021-09-05
sw_fifo.c
//////////////////////////////////////////////////////////////////////////////////////// /* enter necessary header files for proper interrupt vector and UART/USART visibility */ //////////////////////////////////////////////////////////////////////////////////////// #include <sw_fifo.h> typedef struct { uint8_t data_buf[FIFO_BUFFER_SIZE]; // FIFO buffer uint16_t i_first; // index of oldest data byte in buffer uint16_t i_last; //index of newest data byte in buffer uint16_t num_bytes; // number of bytes currently in buffer }sw_fifo_typedef; sw_fifo_typedef rx_fifo = { {0}, 0, 0, 0 }; // declare a receive software buffer sw_fifo_typedef tx_fifo = { {0}, 0, 0, 0 }; // declare a transmit software buffer /***************************************************************************************************************/ // UART receive interrupt sub-routine // - interrupts when valid data exists in rx hardware buffer // - checks if there's room in the rx software buffer // - if there's room, it transfers the received data into the sw buffer // - automatically handles "uart_rx_buffer_full_flag" // - sets overflow flag upon software buffer overflow (doesn't overwrite existing data)////////////////////////////////////////////// /* enter name of UART RX IRQ Handler here */ { ////////////////////////////////////////////// /* Explicitly clear the source of interrupt if necessary */ if(rx_fifo.num_bytes == FIFO_BUFFER_SIZE) { // if the sw buffer is full uart_rx_fifo_ovf_flag = 1; // set the overflow flag }else if(rx_fifo.num_bytes < FIFO_BUFFER_SIZE) { // if there's room in the sw buffer /////////////////////////////////////////////////// /* read error/status reg here if desired */ /* handle any hardware RX errors here if desired */ /////////////////////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// rx_fifo.data_buf[rx_fifo.i_last] = /* enter pointer to UART rx hardware buffer here */ // store the received data as the newest data element in the sw buffer ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// rx_fifo.i_last++; // increment the index of the most recently added element rx_fifo.num_bytes++; // increment the bytes counter } if(rx_fifo.num_bytes == FIFO_BUFFER_SIZE) { // if sw buffer just filled up uart_rx_fifo_full_flag = 1; // set the RX FIFO full flag } if(rx_fifo.i_last == FIFO_BUFFER_SIZE) { // if the index has reached the end of the buffer, rx_fifo.i_last = 0; // roll over the index counter } uart_rx_fifo_not_empty_flag = 1; // set received-data flag } // end UART RX IRQ handler /***************************************************************************************************************/ /***************************************************************************************************************/ // UART transmit interrupt sub-routine // - interrupts when the tx hardware buffer is empty // - checks if data exists in the tx software buffer // - if data exists, it places the oldest element of the sw buffer into the tx hardware buffer // - if the sw buffer is emptied, it disables the "hw buffer empty" interrupt // - automatically handles "uart_tx_buffer_full_flag" ////////////////////////////////////////////// /* enter name of UART TX IRQ Handler here */ { ////////////////////////////////////////////// /* Explicitly clear the source of interrupt if necessary */ if(tx_fifo.num_bytes == FIFO_BUFFER_SIZE) { // if the sw buffer is full uart_tx_fifo_full_flag = 0; // clear the buffer full flag because we are about to make room } if(tx_fifo.num_bytes > 0) { // if data exists in the sw buffer /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// /* enter pointer to UART tx hardware buffer here */ = tx_fifo.data_buf[tx_fifo.i_first]; // place oldest data element in the TX hardware buffer /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// tx_fifo.i_first++; // increment the index of the oldest element tx_fifo.num_bytes--; // decrement the bytes counter } if(tx_fifo.i_first == FIFO_BUFFER_SIZE) { // if the index has reached the end of the buffer, tx_fifo.i_first = 0; // roll over the index counter } if(tx_fifo.num_bytes == 0) { // if no more data exists uart_tx_fifo_not_empty_flag = 0; // clear flag ////////////////////////////////////////////////////////////////////////// /* disable UART "TX hw buffer empty" interrupt here */ /* if using shared RX/TX hardware buffer, enable RX data interrupt here */ ////////////////////////////////////////////////////////////////////////// } }// end UART TX IRQ handler /***************************************************************************************************************/ /***************************************************************************************************************/ // UART data transmit function // - checks if there's room in the transmit sw buffer // - if there's room, it transfers data byte to sw buffer // - automatically handles "uart_tx_buffer_full_flag" // - sets the overflow flag upon software buffer overflow (doesn't overwrite existing data) // - if this is the first data byte in the buffer, it enables the "hw buffer empty" interrupt void uart_send_byte(uint8_t byte) { /////////////////////////////////////////////////////////// /* disable interrupts while manipulating buffer pointers */ /////////////////////////////////////////////////////////// if(tx_fifo.num_bytes == FIFO_BUFFER_SIZE) { // no room in the sw buffer uart_tx_fifo_ovf_flag = 1; // set the overflow flag }else if(tx_fifo.num_bytes < FIFO_BUFFER_SIZE) { // if there's room in the sw buffer tx_fifo.data_buf[tx_fifo.i_last] = byte; // transfer data byte to sw buffer tx_fifo.i_last++; // increment the index of the most recently added element tx_fifo.num_bytes++; // increment the bytes counter } if(tx_fifo.num_bytes == FIFO_BUFFER_SIZE) { // if sw buffer is full uart_tx_fifo_full_flag = 1; // set the TX FIFO full flag } if(tx_fifo.i_last == FIFO_BUFFER_SIZE) { // if the "new data" index has reached the end of the buffer, tx_fifo.i_last = 0; // roll over the index counter } /////////////////////// /* enable interrupts */ /////////////////////// if(tx_fifo.num_bytes > 0) { // if there is data in the buffer uart_tx_fifo_not_empty_flag = 1; // set flag /////////////////////////////////////////////////////////////////////////// /* if using shared RX/TX hardware buffer, disable RX data interrupt here */ /* enable UART "TX hw buffer empty" interrupt here */ /////////////////////////////////////////////////////////////////////////// } } /***************************************************************************************************************/ /***************************************************************************************************************/ // UART data receive function // - checks if data exists in the receive sw buffer // - if data exists, it returns the oldest element contained in the buffer // - automatically handles "uart_rx_buffer_full_flag" // - if no data exists, it clears the uart_rx_flag uint8_t uart_get_byte(void) { /////////////////////////////////////////////////////////// /* disable interrupts while manipulating buffer pointers */ /////////////////////////////////////////////////////////// uint8_t byte = 0; if(rx_fifo.num_bytes == FIFO_BUFFER_SIZE) { // if the sw buffer is full uart_rx_fifo_full_flag = 0; // clear the buffer full flag because we are about to make room } if(rx_fifo.num_bytes > 0) { // if data exists in the sw buffer byte = rx_fifo.data_buf[rx_fifo.i_first]; // grab the oldest element in the buffer rx_fifo.i_first++; // increment the index of the oldest element rx_fifo.num_bytes--; // decrement the bytes counter }else{ // RX sw buffer is empty uart_rx_fifo_not_empty_flag = 0; // clear the rx flag } if(rx_fifo.i_first == FIFO_BUFFER_SIZE) { // if the index has reached the end of the buffer, rx_fifo.i_first = 0; // roll over the index counter } /////////////////////// /* enable interrupts */ /////////////////////// return byte; // return the data byte } /***************************************************************************************************************/
sw_fifo.h
#define FIFO_BUFFER_SIZE 128 // software buffer size (in bytes) // UART data transmit function // - checks if there's room in the transmit sw buffer // - if there's room, it transfers data byte to sw buffer // - automatically handles "uart_tx_buffer_full_flag" // - sets the overflow flag upon software buffer overflow (doesn't overwrite existing data) // - if this is the first data byte in the buffer, it enables the "hw buffer empty" interrupt void uart_send_byte(uint8_t byte); // UART data receive function // - checks if data exists in the receive sw buffer // - if data exists, it returns the oldest element contained in the buffer // - automatically handles "uart_rx_buffer_full_flag" // - if no data exists, it clears the uart_rx_flag uint8_t uart_get_byte(void); volatile extern uint8_t uart_rx_fifo_not_empty_flag; // this flag is automatically set and cleared by the software buffer volatile extern uint8_t uart_rx_fifo_full_flag; // this flag is automatically set and cleared by the software buffer volatile extern uint8_t uart_rx_fifo_ovf_flag; // this flag is not automatically cleared by the software buffer volatile extern uint8_t uart_tx_fifo_full_flag; // this flag is automatically set and cleared by the software buffer volatile extern uint8_t uart_tx_fifo_ovf_flag; // this flag is not automatically cleared by the software buffer volatile extern uint8_t uart_tx_fifo_not_empty_flag; // this flag is automatically set and cleared by the software buffer
copyright
https://forum.digikey.com/t/software-fifo-buffer-for-uart-communication/13476