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Remove the method call from the interrupt handlers. This brings the rx and tx interrupt paths down to < 60 instructions worst case, or ~4us. 

At 115200 we expect ~100us between interrupts, or around 5% CPU overhead.  4us latency is probably acceptable for servo signal jitter too if we decide to consider using the Arduino Servo library.

git-svn-id: https://arducopter.googlecode.com/svn/trunk@513 f9c3cf11-9bcb-44bc-f272-b75c42450872
This commit is contained in:
DrZiplok@gmail.com 2010-09-13 17:44:59 +00:00
parent 813b67cb5e
commit 11865c1718
3 changed files with 368 additions and 388 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

94
libraries/FastSerial/FastSerial.cpp
View File

@ -39,7 +39,8 @@
# define FS_MAX_PORTS 1
#endif
FastSerial *__FastSerial__ports[FS_MAX_PORTS];
FastSerial::Buffer __FastSerial__rxBuffer[FS_MAX_PORTS];
FastSerial::Buffer __FastSerial__txBuffer[FS_MAX_PORTS];
// Default buffer sizes
#define RX_BUFFER_SIZE 128
@ -96,11 +97,10 @@ FastSerial::FastSerial(const uint8_t portNumber,
_portTxBits = portTxBits;
// init buffers
_txBuffer.head = _txBuffer.tail = 0;
_rxBuffer.head = _rxBuffer.tail = 0;
// claim the port
__FastSerial__ports[portNumber] = this;
_rxBuffer = &__FastSerial__rxBuffer[portNumber];
_txBuffer->head = _txBuffer->tail = 0;
_txBuffer = &__FastSerial__txBuffer[portNumber];
_rxBuffer->head = _rxBuffer->tail = 0;
// init stdio
fdev_setup_stream(&_fd, &FastSerial::_putchar, NULL, _FDEV_SETUP_WRITE);
@ -126,8 +126,8 @@ void FastSerial::begin(long baud, unsigned int rxSpace, unsigned int txSpace)
end();
// allocate buffers
if (!_allocBuffer(&_rxBuffer, rxSpace ? : RX_BUFFER_SIZE) ||
!_allocBuffer(&_txBuffer, txSpace ? : TX_BUFFER_SIZE)) {
if (!_allocBuffer(_rxBuffer, rxSpace ? : RX_BUFFER_SIZE) ||
!_allocBuffer(_txBuffer, txSpace ? : TX_BUFFER_SIZE)) {
end();
return; // couldn't allocate buffers - fatal
}
@ -167,8 +167,8 @@ void FastSerial::end()
{
*_ucsrb &= ~(_portEnableBits | _portTxBits);
_freeBuffer(&_rxBuffer);
_freeBuffer(&_txBuffer);
_freeBuffer(_rxBuffer);
_freeBuffer(_txBuffer);
_open = false;
}
@ -177,7 +177,7 @@ FastSerial::available(void)
{
if (!_open)
return(-1);
return((_rxBuffer.head - _rxBuffer.tail) & _rxBuffer.mask);
return((_rxBuffer->head - _rxBuffer->tail) & _rxBuffer->mask);
}
int
@ -186,12 +186,12 @@ FastSerial::read(void)
uint8_t c;
// if the head and tail are equal, the buffer is empty
if (!_open || (_rxBuffer.head == _rxBuffer.tail))
if (!_open || (_rxBuffer->head == _rxBuffer->tail))
return(-1);
// pull character from tail
c = _rxBuffer.bytes[_rxBuffer.tail];
_rxBuffer.tail = (_rxBuffer.tail + 1) & _rxBuffer.mask;
c = _rxBuffer->bytes[_rxBuffer->tail];
_rxBuffer->tail = (_rxBuffer->tail + 1) & _rxBuffer->mask;
return(c);
}
@ -200,20 +200,20 @@ void
FastSerial::flush(void)
{
// don't reverse this or there may be problems if the RX interrupt
// occurs after reading the value of _rxBuffer.head but before writing
// the value to _rxBuffer.tail; the previous value of head
// occurs after reading the value of _rxBuffer->head but before writing
// the value to _rxBuffer->tail; the previous value of head
// may be written to tail, making it appear as if the buffer
// don't reverse this or there may be problems if the RX interrupt
// occurs after reading the value of head but before writing
// the value to tail; the previous value of rx_buffer_head
// may be written to tail, making it appear as if the buffer
// were full, not empty.
_rxBuffer.head = _rxBuffer.tail;
_rxBuffer->head = _rxBuffer->tail;
// don't reverse this or there may be problems if the TX interrupt
// occurs after reading the value of _txBuffer.tail but before writing
// the value to _txBuffer.head.
_txBuffer.tail = _rxBuffer.head;
// occurs after reading the value of _txBuffer->tail but before writing
// the value to _txBuffer->head.
_txBuffer->tail = _rxBuffer->head;
}
void
@ -225,13 +225,13 @@ FastSerial::write(uint8_t c)
return;
// wait for room in the tx buffer
i = (_txBuffer.head + 1) & _txBuffer.mask;
while (i == _txBuffer.tail)
i = (_txBuffer->head + 1) & _txBuffer->mask;
while (i == _txBuffer->tail)
;
// add byte to the buffer
_txBuffer.bytes[_txBuffer.head] = c;
_txBuffer.head = i;
_txBuffer->bytes[_txBuffer->head] = c;
_txBuffer->head = i;
// enable the data-ready interrupt, as it may be off if the buffer is empty
*_ucsrb |= _portTxBits;
@ -287,39 +287,6 @@ FastSerial::printf_P(const char *fmt, ...)
return(i);
}
// Interrupt methods ///////////////////////////////////////////////////////////
void
FastSerial::receive(uint8_t c)
{
uint8_t i;
// if we should be storing the received character into the location
// just before the tail (meaning that the head would advance to the
// current location of the tail), we're about to overflow the buffer
// and so we don't write the character or advance the head.
i = (_rxBuffer.head + 1) & _rxBuffer.mask;
if (i != _rxBuffer.tail) {
_rxBuffer.bytes[_rxBuffer.head] = c;
_rxBuffer.head = i;
}
}
void
FastSerial::transmit(void)
{
// if the buffer is not empty, send the next byte
if (_txBuffer.head != _txBuffer.tail) {
*_udr = _txBuffer.bytes[_txBuffer.tail];
_txBuffer.tail = (_txBuffer.tail + 1) & _txBuffer.mask;
}
// if the buffer is (now) empty, disable the interrupt
if (_txBuffer.head == _txBuffer.tail)
*_ucsrb &= ~_portTxBits;
}
// Buffer management ///////////////////////////////////////////////////////////
bool
@ -330,13 +297,12 @@ FastSerial::_allocBuffer(Buffer *buffer, unsigned int size)
// init buffer state
buffer->head = buffer->tail = 0;
// cap the buffer size
if (size > BUFFER_MAX)
size = BUFFER_MAX;
// compute the power of 2 greater or equal to the requested buffer size
// and then a mask to simplify wrapping operations
shift = 16 - __builtin_clz(size - 1);
// Compute the power of 2 greater or equal to the requested buffer size
// and then a mask to simplify wrapping operations. Using __builtin_clz
// would seem to make sense, but it uses a 256(!) byte table.
// Note that we ignore requests for more than BUFFER_MAX space.
for (shift = 1; (1U << shift) < min(BUFFER_MAX, size); shift++)
;
buffer->mask = (1 << shift) - 1;
// allocate memory for the buffer - if this fails, we fail

58
libraries/FastSerial/FastSerial.h
View File

@ -37,9 +37,6 @@
// wish to use. This is less friendly than the stock Arduino driver,
// but it saves ~200 bytes for every unused port.
//
// To adjust the transmit/receive buffer sizes, change the size of the
// 'bytes' member in the RXBuffer and TXBuffer structures.
//
#ifndef FastSerial_h
#define FastSerial_h
@ -113,9 +110,12 @@ public:
int printf_P(const char *fmt, ...);
FILE *getfd(void) { return &_fd; };
// Interrupt methods
void receive(uint8_t c);
void transmit(void);
// public so the interrupt handlers can see it
struct Buffer {
volatile uint16_t head, tail;
uint16_t mask;
uint8_t *bytes;
};
private:
// register accessors
@ -131,13 +131,8 @@ private:
uint8_t _u2x;
// ring buffers
struct Buffer {
volatile int16_t head, tail;
uint8_t *bytes;
uint16_t mask;
};
Buffer _rxBuffer;
Buffer _txBuffer;
Buffer *_rxBuffer;
Buffer *_txBuffer;
bool _open;
bool _allocBuffer(Buffer *buffer, unsigned int size);
@ -150,18 +145,37 @@ private:
};
// Used by the per-port interrupt vectors
extern FastSerial *__FastSerial__ports[];
extern FastSerial::Buffer __FastSerial__rxBuffer[];
extern FastSerial::Buffer __FastSerial__txBuffer[];
// Generic Rx/Tx vectors for a serial port - needs to know magic numbers
#define FastSerialHandler(_PORT, _RXVECTOR, _TXVECTOR, _UDR) \
#define FastSerialHandler(_PORT, _RXVECTOR, _TXVECTOR, _UDR, _UCSRB, _TXBITS) \
ISR(_RXVECTOR, ISR_BLOCK) \
{ \
unsigned char c = _UDR; \
__FastSerial__ports[_PORT]->receive(c); \
uint8_t c; \
int16_t i; \
\
/* read the byte as quickly as possible */ \
c = _UDR; \
/* work out where the head will go next */ \
i = (__FastSerial__rxBuffer[_PORT].head + 1) & __FastSerial__rxBuffer[_PORT].mask; \
/* decide whether we have space for another byte */ \
if (i != __FastSerial__rxBuffer[_PORT].tail) { \
/* we do, move the head */ \
__FastSerial__rxBuffer[_PORT].bytes[__FastSerial__rxBuffer[_PORT].head] = c; \
__FastSerial__rxBuffer[_PORT].head = i; \
} \
} \
ISR(_TXVECTOR, ISR_BLOCK) \
{ \
__FastSerial__ports[_PORT]->transmit(); \
/* if we have taken an interrupt we are ready to transmit the next byte */ \
_UDR = __FastSerial__txBuffer[_PORT].bytes[__FastSerial__txBuffer[_PORT].tail]; \
/* increment the tail */ \
__FastSerial__txBuffer[_PORT].tail = \
(__FastSerial__txBuffer[_PORT].tail + 1) & __FastSerial__txBuffer[_PORT].mask; \
/* if there are no more bytes to send, disable the interrupt */ \
if (__FastSerial__txBuffer[_PORT].head == __FastSerial__txBuffer[_PORT].tail) \
_UCSRB &= ~_TXBITS; \
} \
struct hack
@ -177,7 +191,7 @@ struct hack
U2X0, \
(_BV(RXEN0) | _BV(TXEN0) | _BV(RXCIE0)), \
(_BV(UDRIE0))); \
FastSerialHandler(0, SIG_USART0_RECV, SIG_USART0_DATA, UDR0)
FastSerialHandler(0, SIG_USART0_RECV, SIG_USART0_DATA, UDR0, UCSR0B, _BV(UDRIE0))
#if defined(__AVR_ATmega1280__)
#define FastSerialPort1(_portName) \
FastSerial _portName(1, \
@ -189,7 +203,7 @@ struct hack
U2X1, \
(_BV(RXEN1) | _BV(TXEN1) | _BV(RXCIE1)), \
(_BV(UDRIE1))); \
FastSerialHandler(1, SIG_USART1_RECV, SIG_USART1_DATA, UDR1)
FastSerialHandler(1, SIG_USART1_RECV, SIG_USART1_DATA, UDR1, UCSR1B, _BV(UDRIE1))
#define FastSerialPort2(_portName) \
FastSerial _portName(2, \
&UBRR2H, \
@ -200,7 +214,7 @@ struct hack
U2X2, \
(_BV(RXEN2) | _BV(TXEN2) | _BV(RXCIE2)), \
(_BV(UDRIE2))); \
FastSerialHandler(2, SIG_USART2_RECV, SIG_USART2_DATA, UDR2)
FastSerialHandler(2, SIG_USART2_RECV, SIG_USART2_DATA, UDR2, UCSR2B, _BV(UDRIE2))
#define FastSerialPort3(_portName) \
FastSerial _portName(3, \
&UBRR3H, \
@ -211,7 +225,7 @@ struct hack
U2X3, \
(_BV(RXEN3) | _BV(TXEN3) | _BV(RXCIE3)), \
(_BV(UDRIE3))); \
FastSerialHandler(3, SIG_USART3_RECV, SIG_USART3_DATA, UDR3)
FastSerialHandler(3, SIG_USART3_RECV, SIG_USART3_DATA, UDR3, UCSR3B, _BV(UDRIE3))
#endif
#endif // FastSerial_h

4
libraries/FastSerial/examples/FastSerial/FastSerial.pde
View File

@ -22,9 +22,9 @@ FastSerialPort0(Serial);
//
// To create a driver for a different serial port, on a board that
// supports more than one, pass an argument to the constructor:
// supports more than one, use the appropriate macro:
//
//FastSerial Serial2(2);
//FastSerialPort2(Serial2);
void setup(void)