Commit 79742c5d authored by Dean Camera's avatar Dean Camera
Browse files

Make software USART used in the XPLAINBridge project directly check and store...

Make software USART used in the XPLAINBridge project directly check and store into the ring buffers, rather than polling from the main program loop to avoid added latency.
parent 9b29d1dc
......@@ -53,13 +53,15 @@
RingBuff_Data_t Buffer[BUFFER_SIZE];
RingBuff_Data_t* In;
RingBuff_Data_t* Out;
uint8_t Count;
} RingBuff_t;
/* Inline Functions: */
static inline void RingBuffer_InitBuffer(RingBuff_t* const Buffer)
{
Buffer->In = Buffer->Buffer;
Buffer->Out = Buffer->Buffer;
Buffer->Out = Buffer->Buffer;
Buffer->Count = 0;
}
static inline void RingBuffer_Insert(RingBuff_t* const Buffer, RingBuff_Data_t Data)
......@@ -68,6 +70,8 @@
if (++Buffer->In == &Buffer->Buffer[BUFFER_SIZE])
Buffer->In = Buffer->Buffer;
Buffer->Count++;
}
static inline RingBuff_Data_t RingBuffer_Remove(RingBuff_t* const Buffer)
......@@ -77,12 +81,9 @@
if (++Buffer->Out == &Buffer->Buffer[BUFFER_SIZE])
Buffer->Out = Buffer->Buffer;
return Data;
}
Buffer->Count--;
static inline bool RingBuffer_Empty(RingBuff_t* const Buffer)
{
return (Buffer->In == Buffer->Out);
return Data;
}
#endif
......@@ -30,27 +30,16 @@
this software.
*/
#include "SoftUART.h"
volatile bool srx_done;
volatile uint8_t stx_count;
static uint8_t srx_data, srx_mask, srx_tmp, stx_data;
void SoftUART_TxByte(uint8_t Byte)
{
while (stx_count);
/** \file
*
* Software UART for both data transmission and reception. This
* code continuously monitors the ring buffers set up by the main
* project source file and reads/writes data as it becomes available.
*/
stx_data = ~Byte;
stx_count = 10;
}
uint8_t SoftUART_RxByte(void)
{
while (!(srx_done));
srx_done = false;
#include "SoftUART.h"
return srx_data;
}
static uint8_t TX_BitsRemaining, TX_Data, RX_BitMask, RX_Data;
void SoftUART_Init(void)
{
......@@ -61,8 +50,7 @@ void SoftUART_Init(void)
EICRA = (1 << ISC01); // -ve edge
EIMSK = (1 << INT0); // enable INT0 interrupt
stx_count = 0; // nothing to send
srx_done = false; // nothing received
TX_BitsRemaining = 0; // nothing to send
STXPORT |= (1 << STX); // TX output
STXDDR |= (1 << STX); // TX output
SRXPORT |= (1 << SRX); // pullup on INT0
......@@ -73,8 +61,8 @@ ISR(INT0_vect)
{
OCR2A = TCNT2 + (BIT_TIME / 8 * 3 / 2); // scan 1.5 bits after start
srx_tmp = 0; // clear bit storage
srx_mask = 1; // bit mask
RX_Data = 0; // clear bit storage
RX_BitMask = (1 << 0); // bit mask
TIFR2 = (1 << OCF2A); // clear pending interrupt
......@@ -88,19 +76,19 @@ ISR(INT0_vect)
/* ISR to manage the reception of bits to the transmitter. */
ISR(TIMER2_COMPA_vect)
{
if (srx_mask)
if (RX_BitMask)
{
if (SRXPIN & (1 << SRX))
srx_tmp |= srx_mask;
RX_Data |= RX_BitMask;
srx_mask <<= 1;
RX_BitMask <<= 1;
OCR2A += BIT_TIME / 8; // next bit slice
}
else
{
srx_done = true; // mark rx data valid
srx_data = srx_tmp; // store rx data
RingBuffer_Insert(&UARTtoUSB_Buffer, RX_Data);
TIMSK2 = (1 << OCIE2B); // enable tx and wait for start
EIMSK |= (1 << INT0); // enable START irq
EIFR = (1 << INTF0); // clear any pending
......@@ -112,20 +100,25 @@ ISR(TIMER2_COMPB_vect)
{
OCR2B += BIT_TIME / 8; // next bit slice
if (stx_count)
if (TX_BitsRemaining)
{
if (--stx_count != 9) // no start bit
if (--TX_BitsRemaining != 9) // no start bit
{
if (!(stx_data & 1)) // test inverted data
TCCR2A = (1 << COM2B1) | (1 << COM2B0);
else
if (TX_Data & (1 << 0)) // test inverted data
TCCR2A = (1 << COM2B1);
else
TCCR2A = (1 << COM2B1) | (1 << COM2B0);
stx_data >>= 1; // shift zero in from left
TX_Data >>= 1; // shift zero in from left
}
else
{
TCCR2A = (1 << COM2B1); // START bit
}
}
else if (USBtoUART_Buffer.Count)
{
TX_Data = ~RingBuffer_Remove(&USBtoUART_Buffer);
TX_BitsRemaining = 10;
}
}
......@@ -37,6 +37,9 @@
#include <avr/io.h>
#include <avr/interrupt.h>
#include <stdbool.h>
#include "../XPLAINBridge.h"
#include "LightweightRingBuff.h"
/* Macros: */
#define BAUD 9600
......@@ -50,24 +53,7 @@
#define STXPORT PORTD
#define STXDDR DDRD
/* External Variables: */
extern volatile bool srx_done;
extern volatile uint8_t stx_count;
/* Inline Functions: */
static inline bool SoftUART_IsReady(void)
{
return !(stx_count);
}
static inline bool SoftUART_IsReceived(void)
{
return srx_done;
}
/* Function Prototypes: */
void SoftUART_TxByte(uint8_t c);
uint8_t SoftUART_RxByte(void);
void SoftUART_Init(void);
#endif
\ No newline at end of file
......@@ -125,17 +125,9 @@ void USARTBridge_Task(void)
RingBuffer_Insert(&USBtoUART_Buffer, CDC_Device_ReceiveByte(&VirtualSerial_CDC_Interface));
/* Read bytes from the UART receive buffer into the USB IN endpoint */
if (!(RingBuffer_Empty(&UARTtoUSB_Buffer)))
if (UARTtoUSB_Buffer.Count)
CDC_Device_SendByte(&VirtualSerial_CDC_Interface, RingBuffer_Remove(&UARTtoUSB_Buffer));
/* Load bytes from the UART transmit buffer into the UART */
if (!(RingBuffer_Empty(&USBtoUART_Buffer)) && SoftUART_IsReady())
SoftUART_TxByte(RingBuffer_Remove(&USBtoUART_Buffer));
/* Load bytes from the UART into the UART receive buffer */
if (SoftUART_IsReceived())
RingBuffer_Insert(&UARTtoUSB_Buffer, SoftUART_RxByte());
CDC_Device_USBTask(&VirtualSerial_CDC_Interface);
}
......
......@@ -77,7 +77,9 @@
#define MODE_PDI_PROGRAMMER true
/* External Variables: */
extern bool CurrentFirmwareMode;
extern bool CurrentFirmwareMode;
extern RingBuff_t UARTtoUSB_Buffer;
extern RingBuff_t USBtoUART_Buffer;
/* Function Prototypes: */
void SetupHardware(void);
......
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