From 79742c5d24929442175953c796a1834e45a93d0d Mon Sep 17 00:00:00 2001
From: Dean Camera <dean@fourwalledcubicle.com>
Date: Wed, 26 May 2010 06:59:55 +0000
Subject: [PATCH] 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.
---
.../XPLAINBridge/Lib/LightweightRingBuff.h | 13 ++--
Projects/XPLAINBridge/Lib/SoftUART.c | 61 ++++++++-----------
Projects/XPLAINBridge/Lib/SoftUART.h | 20 +-----
Projects/XPLAINBridge/XPLAINBridge.c | 12 +---
Projects/XPLAINBridge/XPLAINBridge.h | 4 +-
5 files changed, 42 insertions(+), 68 deletions(-)
diff --git a/Projects/XPLAINBridge/Lib/LightweightRingBuff.h b/Projects/XPLAINBridge/Lib/LightweightRingBuff.h
index 16e890c07..31430ddd4 100644
--- a/Projects/XPLAINBridge/Lib/LightweightRingBuff.h
+++ b/Projects/XPLAINBridge/Lib/LightweightRingBuff.h
@@ -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
diff --git a/Projects/XPLAINBridge/Lib/SoftUART.c b/Projects/XPLAINBridge/Lib/SoftUART.c
index 5e589f3d7..18d5c01bd 100644
--- a/Projects/XPLAINBridge/Lib/SoftUART.c
+++ b/Projects/XPLAINBridge/Lib/SoftUART.c
@@ -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;
+ }
}
diff --git a/Projects/XPLAINBridge/Lib/SoftUART.h b/Projects/XPLAINBridge/Lib/SoftUART.h
index 416490d8d..e54d4a9ae 100644
--- a/Projects/XPLAINBridge/Lib/SoftUART.h
+++ b/Projects/XPLAINBridge/Lib/SoftUART.h
@@ -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
diff --git a/Projects/XPLAINBridge/XPLAINBridge.c b/Projects/XPLAINBridge/XPLAINBridge.c
index 5798c21a5..d92e2b493 100644
--- a/Projects/XPLAINBridge/XPLAINBridge.c
+++ b/Projects/XPLAINBridge/XPLAINBridge.c
@@ -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);
}
diff --git a/Projects/XPLAINBridge/XPLAINBridge.h b/Projects/XPLAINBridge/XPLAINBridge.h
index ddb5b0e0c..72e90463d 100644
--- a/Projects/XPLAINBridge/XPLAINBridge.h
+++ b/Projects/XPLAINBridge/XPLAINBridge.h
@@ -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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