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