MPCNC/Firmware
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Fix serial XON/XOFF handshaking

Browse Source 
Co-Authored-By: ejtagle <ejtagle@hotmail.com>
This commit is contained in:
Scott Lahteine 2018-06-09 21:39:57 -05:00
parent 63af814d4d
commit 17a965de17
2 changed files with 269 additions and 164 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

412
Marlin/MarlinSerial.cpp
View File

@ -55,16 +55,15 @@
ring_buffer_r rx_buffer = { { 0 }, 0, 0 };
#if TX_BUFFER_SIZE > 0
ring_buffer_t tx_buffer = { { 0 }, 0, 0 };
static bool _written;
#endif
static bool _written;
#endif
#if ENABLED(SERIAL_XON_XOFF)
constexpr uint8_t XON_XOFF_CHAR_SENT = 0x80; // XON / XOFF Character was sent
constexpr uint8_t XON_XOFF_CHAR_MASK = 0x1F; // XON / XOFF character to send
constexpr uint8_t XON_XOFF_CHAR_SENT = 0x80, // XON / XOFF Character was sent
XON_XOFF_CHAR_MASK = 0x1F; // XON / XOFF character to send
// XON / XOFF character definitions
constexpr uint8_t XON_CHAR = 17;
constexpr uint8_t XOFF_CHAR = 19;
constexpr uint8_t XON_CHAR = 17, XOFF_CHAR = 19;
uint8_t xon_xoff_state = XON_XOFF_CHAR_SENT | XON_CHAR;
#endif
@ -85,123 +84,197 @@
// (called with RX interrupts disabled)
FORCE_INLINE void store_rxd_char() {
const ring_buffer_pos_t h = rx_buffer.head,
i = (ring_buffer_pos_t)(h + 1) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
// Get the tail - Nothing can alter its value while we are at this ISR
const ring_buffer_pos_t t = rx_buffer.tail;
// Get the head pointer
ring_buffer_pos_t h = rx_buffer.head;
// Get the next element
ring_buffer_pos_t i = (ring_buffer_pos_t)(h + 1) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
// Read the character from the USART
uint8_t c = M_UDRx;
#if ENABLED(EMERGENCY_PARSER)
emergency_parser.update(c);
#endif
// If the character is to be stored at the index just before the tail
// (such that the head would advance to the current tail), the buffer is
// critical, so don't write the character or advance the head.
const char c = M_UDRx;
if (i != rx_buffer.tail) {
// (such that the head would advance to the current tail), the RX FIFO is
// full, so don't write the character or advance the head.
if (i != t) {
rx_buffer.buffer[h] = c;
rx_buffer.head = i;
}
else {
#if ENABLED(SERIAL_STATS_DROPPED_RX)
if (!++rx_dropped_bytes) ++rx_dropped_bytes;
#endif
h = i;
}
#if ENABLED(SERIAL_STATS_DROPPED_RX)
else if (!++rx_dropped_bytes) --rx_dropped_bytes;
#endif
#if ENABLED(SERIAL_STATS_MAX_RX_QUEUED)
// calculate count of bytes stored into the RX buffer
ring_buffer_pos_t rx_count = (ring_buffer_pos_t)(rx_buffer.head - rx_buffer.tail) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
// Calculate count of bytes stored into the RX buffer
const ring_buffer_pos_t rx_count = (ring_buffer_pos_t)(h - t) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
// Keep track of the maximum count of enqueued bytes
NOLESS(rx_max_enqueued, rx_count);
#endif
#if ENABLED(SERIAL_XON_XOFF)
// for high speed transfers, we can use XON/XOFF protocol to do
// software handshake and avoid overruns.
// If the last char that was sent was an XON
if ((xon_xoff_state & XON_XOFF_CHAR_MASK) == XON_CHAR) {
// calculate count of bytes stored into the RX buffer
ring_buffer_pos_t rx_count = (ring_buffer_pos_t)(rx_buffer.head - rx_buffer.tail) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
// Bytes stored into the RX buffer
const ring_buffer_pos_t rx_count = (ring_buffer_pos_t)(h - t) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
// if we are above 12.5% of RX buffer capacity, send XOFF before
// we run out of RX buffer space .. We need 325 bytes @ 250kbits/s to
// let the host react and stop sending bytes. This translates to 13mS
// propagation time.
// If over 12.5% of RX buffer capacity, send XOFF before running out of
// RX buffer space .. 325 bytes @ 250kbits/s needed to let the host react
// and stop sending bytes. This translates to 13mS propagation time.
if (rx_count >= (RX_BUFFER_SIZE) / 8) {
// If TX interrupts are disabled and data register is empty,
// just write the byte to the data register and be done. This
// shortcut helps significantly improve the effective datarate
// at high (>500kbit/s) bitrates, where interrupt overhead
// becomes a slowdown.
if (!TEST(M_UCSRxB, M_UDRIEx) && TEST(M_UCSRxA, M_UDREx)) {
// At this point, definitely no TX interrupt was executing, since the TX isr can't be preempted.
// Don't enable the TX interrupt here as a means to trigger the XOFF char, because if it happens
// to be in the middle of trying to disable the RX interrupt in the main program, eventually the
// enabling of the TX interrupt could be undone. The ONLY reliable thing this can do to ensure
// the sending of the XOFF char is to send it HERE AND NOW.
// Send an XOFF character
M_UDRx = XOFF_CHAR;
// About to send the XOFF char
xon_xoff_state = XOFF_CHAR | XON_XOFF_CHAR_SENT;
// clear the TXC bit -- "can be cleared by writing a one to its bit
// location". This makes sure flush() won't return until the bytes
// actually got written
SBI(M_UCSRxA, M_TXCx);
// Wait until the TX register becomes empty and send it - Here there could be a problem
// - While waiting for the TX register to empty, the RX register could receive a new
// character. This must also handle that situation!
while (!TEST(M_UCSRxA, M_UDREx)) {
// And remember it was sent
xon_xoff_state = XOFF_CHAR | XON_XOFF_CHAR_SENT;
if (TEST(M_UCSRxA,M_RXCx)) {
// A char arrived while waiting for the TX buffer to be empty - Receive and process it!
i = (ring_buffer_pos_t)(h + 1) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
// Read the character from the USART
c = M_UDRx;
#if ENABLED(EMERGENCY_PARSER)
emergency_parser.update(c);
#endif
// If the character is to be stored at the index just before the tail
// (such that the head would advance to the current tail), the FIFO is
// full, so don't write the character or advance the head.
if (i != t) {
rx_buffer.buffer[h] = c;
h = i;
}
#if ENABLED(SERIAL_STATS_DROPPED_RX)
else if (!++rx_dropped_bytes) --rx_dropped_bytes;
#endif
}
sw_barrier();
}
else {
// TX interrupts disabled, but buffer still not empty ... or
// TX interrupts enabled. Reenable TX ints and schedule XOFF
// character to be sent
#if TX_BUFFER_SIZE > 0
SBI(M_UCSRxB, M_UDRIEx);
xon_xoff_state = XOFF_CHAR;
#else
// We are not using TX interrupts, we will have to send this manually
while (!TEST(M_UCSRxA, M_UDREx)) sw_barrier();
M_UDRx = XOFF_CHAR;
// clear the TXC bit -- "can be cleared by writing a one to its bit
// location". This makes sure flush() won't return until the bytes
// actually got written
SBI(M_UCSRxA, M_TXCx);
M_UDRx = XOFF_CHAR;
// And remember we already sent it
xon_xoff_state = XOFF_CHAR | XON_XOFF_CHAR_SENT;
#endif
// Clear the TXC bit -- "can be cleared by writing a one to its bit
// location". This makes sure flush() won't return until the bytes
// actually got written
SBI(M_UCSRxA, M_TXCx);
// At this point there could be a race condition between the write() function
// and this sending of the XOFF char. This interrupt could happen between the
// wait to be empty TX buffer loop and the actual write of the character. Since
// the TX buffer is full because it's sending the XOFF char, the only way to be
// sure the write() function will succeed is to wait for the XOFF char to be
// completely sent. Since an extra character could be received during the wait
// it must also be handled!
while (!TEST(M_UCSRxA, M_UDREx)) {
if (TEST(M_UCSRxA,M_RXCx)) {
// A char arrived while waiting for the TX buffer to be empty - Receive and process it!
i = (ring_buffer_pos_t)(h + 1) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
// Read the character from the USART
c = M_UDRx;
#if ENABLED(EMERGENCY_PARSER)
emergency_parser.update(c);
#endif
// If the character is to be stored at the index just before the tail
// (such that the head would advance to the current tail), the FIFO is
// full, so don't write the character or advance the head.
if (i != t) {
rx_buffer.buffer[h] = c;
h = i;
}
#if ENABLED(SERIAL_STATS_DROPPED_RX)
else if (!++rx_dropped_bytes) --rx_dropped_bytes;
#endif
}
sw_barrier();
}
// At this point everything is ready. The write() function won't
// have any issues writing to the UART TX register if it needs to!
}
}
#endif // SERIAL_XON_XOFF
#if ENABLED(EMERGENCY_PARSER)
emergency_parser.update(c);
#endif
// Store the new head value
rx_buffer.head = h;
}
#if TX_BUFFER_SIZE > 0
// (called with TX irqs disabled)
FORCE_INLINE void _tx_udr_empty_irq(void) {
// If interrupts are enabled, there must be more data in the output
// buffer.
// Read positions
uint8_t t = tx_buffer.tail;
const uint8_t h = tx_buffer.head;
#if ENABLED(SERIAL_XON_XOFF)
// Do a priority insertion of an XON/XOFF char, if needed.
const uint8_t state = xon_xoff_state;
if (!(state & XON_XOFF_CHAR_SENT)) {
M_UDRx = state & XON_XOFF_CHAR_MASK;
xon_xoff_state = state | XON_XOFF_CHAR_SENT;
// If an XON char is pending to be sent, do it now
if (xon_xoff_state == XON_CHAR) {
// Send the character
M_UDRx = XON_CHAR;
// clear the TXC bit -- "can be cleared by writing a one to its bit
// location". This makes sure flush() won't return until the bytes
// actually got written
SBI(M_UCSRxA, M_TXCx);
// Remember we sent it.
xon_xoff_state = XON_CHAR | XON_XOFF_CHAR_SENT;
// If nothing else to transmit, just disable TX interrupts.
if (h == t) CBI(M_UCSRxB, M_UDRIEx); // (Non-atomic, could be reenabled by the main program, but eventually this will succeed)
return;
}
else
#endif
{ // Send the next byte
const uint8_t t = tx_buffer.tail, c = tx_buffer.buffer[t];
tx_buffer.tail = (t + 1) & (TX_BUFFER_SIZE - 1);
M_UDRx = c;
// If nothing to transmit, just disable TX interrupts. This could
// happen as the result of the non atomicity of the disabling of RX
// interrupts that could end reenabling TX interrupts as a side effect.
if (h == t) {
CBI(M_UCSRxB, M_UDRIEx); // (Non-atomic, could be reenabled by the main program, but eventually this will succeed)
return;
}
// clear the TXC bit -- "can be cleared by writing a one to its bit
// location". This makes sure flush() won't return until the bytes
// actually got written
// There is something to TX, Send the next byte
const uint8_t c = tx_buffer.buffer[t];
t = (t + 1) & (TX_BUFFER_SIZE - 1);
M_UDRx = c;
tx_buffer.tail = t;
// Clear the TXC bit (by writing a one to its bit location).
// Ensures flush() won't return until the bytes are actually written/
SBI(M_UCSRxA, M_TXCx);
// Disable interrupts if the buffer is empty
if (tx_buffer.head == tx_buffer.tail)
CBI(M_UCSRxB, M_UDRIEx);
// Disable interrupts if there is nothing to transmit following this byte
if (h == t) CBI(M_UCSRxB, M_UDRIEx); // (Non-atomic, could be reenabled by the main program, but eventually this will succeed)
}
#ifdef M_USARTx_UDRE_vect
@ -245,8 +318,8 @@
SBI(M_UCSRxB, M_RXCIEx);
#if TX_BUFFER_SIZE > 0
CBI(M_UCSRxB, M_UDRIEx);
_written = false;
#endif
_written = false;
}
void MarlinSerial::end() {
@ -273,11 +346,11 @@
}
int MarlinSerial::read(void) {
int v;
#if RX_BUFFER_SIZE > 256
// Disable RX interrupts to ensure atomic reads
const bool isr_enabled = TEST(M_UCSRxB, M_RXCIEx);
// Disable RX interrupts to ensure atomic reads - This could reenable TX interrupts,
// but this situation is explicitly handled at the TX isr, so no problems there
bool isr_enabled = TEST(M_UCSRxB, M_RXCIEx);
CBI(M_UCSRxB, M_RXCIEx);
#endif
@ -290,43 +363,50 @@
ring_buffer_pos_t t = rx_buffer.tail;
if (h == t)
v = -1;
else {
v = rx_buffer.buffer[t];
t = (ring_buffer_pos_t)(t + 1) & (RX_BUFFER_SIZE - 1);
// If nothing to read, return now
if (h == t) return -1;
#if RX_BUFFER_SIZE > 256
// Disable RX interrupts to ensure atomic write to tail, so
// the RX isr can't read partially updated values
const bool isr_enabled = TEST(M_UCSRxB, M_RXCIEx);
CBI(M_UCSRxB, M_RXCIEx);
#endif
// Get the next char
const int v = rx_buffer.buffer[t];
t = (ring_buffer_pos_t)(t + 1) & (RX_BUFFER_SIZE - 1);
// Advance tail
rx_buffer.tail = t;
#if RX_BUFFER_SIZE > 256
// Disable RX interrupts to ensure atomic write to tail, so
// the RX isr can't read partially updated values - This could
// reenable TX interrupts, but this situation is explicitly
// handled at the TX isr, so no problems there
isr_enabled = TEST(M_UCSRxB, M_RXCIEx);
CBI(M_UCSRxB, M_RXCIEx);
#endif
#if RX_BUFFER_SIZE > 256
// End critical section
if (isr_enabled) SBI(M_UCSRxB, M_RXCIEx);
#endif
// Advance tail
rx_buffer.tail = t;
#if ENABLED(SERIAL_XON_XOFF)
if ((xon_xoff_state & XON_XOFF_CHAR_MASK) == XOFF_CHAR) {
#if RX_BUFFER_SIZE > 256
// End critical section
if (isr_enabled) SBI(M_UCSRxB, M_RXCIEx);
#endif
// Get count of bytes in the RX buffer
ring_buffer_pos_t rx_count = (ring_buffer_pos_t)(h - t) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
// When below 10% of RX buffer capacity, send XON before
// running out of RX buffer bytes
if (rx_count < (RX_BUFFER_SIZE) / 10) {
#if ENABLED(SERIAL_XON_XOFF)
// If the XOFF char was sent, or about to be sent...
if ((xon_xoff_state & XON_XOFF_CHAR_MASK) == XOFF_CHAR) {
// Get count of bytes in the RX buffer
const ring_buffer_pos_t rx_count = (ring_buffer_pos_t)(h - t) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
if (rx_count < (RX_BUFFER_SIZE) / 10) {
#if TX_BUFFER_SIZE > 0
// Signal we want an XON character to be sent.
xon_xoff_state = XON_CHAR;
// Enable TX isr. Non atomic, but it will eventually enable them
SBI(M_UCSRxB, M_UDRIEx);
#else
// If not using TX interrupts, we must send the XON char now
xon_xoff_state = XON_CHAR | XON_XOFF_CHAR_SENT;
write(XON_CHAR);
return v;
}
while (!TEST(M_UCSRxA, M_UDREx)) sw_barrier();
M_UDRx = XON_CHAR;
#endif
}
#endif
}
}
#endif
return v;
}
@ -337,7 +417,7 @@
CBI(M_UCSRxB, M_RXCIEx);
#endif
const ring_buffer_pos_t h = rx_buffer.head, t = rx_buffer.tail;
const ring_buffer_pos_t h = rx_buffer.head, t = rx_buffer.tail;
#if RX_BUFFER_SIZE > 256
if (isr_enabled) SBI(M_UCSRxB, M_RXCIEx);
@ -359,9 +439,19 @@
#endif
#if ENABLED(SERIAL_XON_XOFF)
// If the XOFF char was sent, or about to be sent...
if ((xon_xoff_state & XON_XOFF_CHAR_MASK) == XOFF_CHAR) {
xon_xoff_state = XON_CHAR | XON_XOFF_CHAR_SENT;
write(XON_CHAR);
#if TX_BUFFER_SIZE > 0
// Signal we want an XON character to be sent.
xon_xoff_state = XON_CHAR;
// Enable TX isr. Non atomic, but it will eventually enable it.
SBI(M_UCSRxB, M_UDRIEx);
#else
// If not using TX interrupts, we must send the XON char now
xon_xoff_state = XON_CHAR | XON_XOFF_CHAR_SENT;
while (!TEST(M_UCSRxA, M_UDREx)) sw_barrier();
M_UDRx = XON_CHAR;
#endif
}
#endif
}
@ -375,6 +465,8 @@
// be done. This shortcut helps significantly improve the
// effective datarate at high (>500kbit/s) bitrates, where
// interrupt overhead becomes a slowdown.
// Yes, there is a race condition between the sending of the
// XOFF char at the RX isr, but it is properly handled there
if (!TEST(M_UCSRxB, M_UDRIEx) && TEST(M_UCSRxA, M_UDREx)) {
M_UDRx = c;
@ -387,61 +479,79 @@
const uint8_t i = (tx_buffer.head + 1) & (TX_BUFFER_SIZE - 1);
// If the output buffer is full, there's nothing for it other than to
// wait for the interrupt handler to empty it a bit
while (i == tx_buffer.tail) {
if (!ISRS_ENABLED()) {
// Interrupts are disabled, so we'll have to poll the data
// register empty flag ourselves. If it is set, pretend an
// interrupt has happened and call the handler to free up
// space for us.
if (TEST(M_UCSRxA, M_UDREx))
_tx_udr_empty_irq();
}
// (else , the interrupt handler will free up space for us)
// If global interrupts are disabled (as the result of being called from an ISR)...
if (!ISRS_ENABLED()) {
// Make sure compiler rereads tx_buffer.tail
sw_barrier();
// Make room by polling if it is possible to transmit, and do so!
while (i == tx_buffer.tail) {
// If we can transmit another byte, do it.
if (TEST(M_UCSRxA, M_UDREx)) _tx_udr_empty_irq();
// Make sure compiler rereads tx_buffer.tail
sw_barrier();
}
}
else {
// Interrupts are enabled, just wait until there is space
while (i == tx_buffer.tail) { sw_barrier(); }
}
// Store new char. head is always safe to move
tx_buffer.buffer[tx_buffer.head] = c;
tx_buffer.head = i;
// Enable TX isr
// Enable TX isr - Non atomic, but it will eventually enable TX isr
SBI(M_UCSRxB, M_UDRIEx);
return;
}
void MarlinSerial::flushTX(void) {
// TX
// If we have never written a byte, no need to flush. This special
// case is needed since there is no way to force the TXC (transmit
// complete) bit to 1 during initialization
if (!_written)
return;
// No bytes written, no need to flush. This special case is needed since there's
// no way to force the TXC (transmit complete) bit to 1 during initialization.
if (!_written) return;
while (TEST(M_UCSRxB, M_UDRIEx) || !TEST(M_UCSRxA, M_TXCx)) {
if (!ISRS_ENABLED()) {
// Interrupts are globally disabled, but the DR empty
// interrupt should be enabled, so poll the DR empty flag to
// prevent deadlock
// If global interrupts are disabled (as the result of being called from an ISR)...
if (!ISRS_ENABLED()) {
// Wait until everything was transmitted - We must do polling, as interrupts are disabled
while (tx_buffer.head != tx_buffer.tail || !TEST(M_UCSRxA, M_TXCx)) {
// If there is more space, send an extra character
if (TEST(M_UCSRxA, M_UDREx))
_tx_udr_empty_irq();
sw_barrier();
}
sw_barrier();
}
// If we get here, nothing is queued anymore (DRIE is disabled) and
else {
// Wait until everything was transmitted
while (tx_buffer.head != tx_buffer.tail || !TEST(M_UCSRxA, M_TXCx)) sw_barrier();
}
// At this point nothing is queued anymore (DRIE is disabled) and
// the hardware finished transmission (TXC is set).
}
#else // TX_BUFFER_SIZE == 0
void MarlinSerial::write(const uint8_t c) {
_written = true;
while (!TEST(M_UCSRxA, M_UDREx)) sw_barrier();
M_UDRx = c;
}
void MarlinSerial::flushTX(void) {
// No bytes written, no need to flush. This special case is needed since there's
// no way to force the TXC (transmit complete) bit to 1 during initialization.
if (!_written) return;
// Wait until everything was transmitted
while (!TEST(M_UCSRxA, M_TXCx)) sw_barrier();
// At this point nothing is queued anymore (DRIE is disabled) and
// the hardware finished transmission (TXC is set).
}
#endif // TX_BUFFER_SIZE == 0
/**
@ -465,13 +575,9 @@
}
void MarlinSerial::print(long n, int base) {
if (base == 0)
write(n);
if (base == 0) write(n);
else if (base == 10) {
if (n < 0) {
print('-');
n = -n;
}
if (n < 0) { print('-'); n = -n; }
printNumber(n, 10);
}
else

21
Marlin/MarlinSerial.h
View File

@ -26,10 +26,11 @@
*
* Modified 28 September 2010 by Mark Sproul
* Modified 14 February 2016 by Andreas Hardtung (added tx buffer)
* Modified 01 October 2017 by Eduardo José Tagle (added XON/XOFF)
*/
#ifndef MARLINSERIAL_H
#define MARLINSERIAL_H
#ifndef _MARLINSERIAL_H_
#define _MARLINSERIAL_H_
#include "MarlinConfig.h"
@ -112,9 +113,7 @@
static void flush(void);
static ring_buffer_pos_t available(void);
static void write(const uint8_t c);
#if TX_BUFFER_SIZE > 0
static void flushTX(void);
#endif
static void flushTX(void);
#if ENABLED(SERIAL_STATS_DROPPED_RX)
FORCE_INLINE static uint32_t dropped() { return rx_dropped_bytes; }
@ -124,11 +123,6 @@
FORCE_INLINE static ring_buffer_pos_t rxMaxEnqueued() { return rx_max_enqueued; }
#endif
private:
static void printNumber(unsigned long, const uint8_t);
static void printFloat(double, uint8_t);
public:
FORCE_INLINE static void write(const char* str) { while (*str) write(*str++); }
FORCE_INLINE static void write(const uint8_t* buffer, size_t size) { while (size--) write(*buffer++); }
FORCE_INLINE static void print(const String& s) { for (int i = 0; i < (int)s.length(); i++) write(s[i]); }
@ -152,6 +146,11 @@
static void println(unsigned long, int = DEC);
static void println(double, int = 2);
static void println(void);
operator bool() { return true; }
private:
static void printNumber(unsigned long, const uint8_t);
static void printFloat(double, uint8_t);
};
extern MarlinSerial customizedSerial;
@ -163,4 +162,4 @@
extern HardwareSerial bluetoothSerial;
#endif
#endif // MARLINSERIAL_H
#endif // _MARLINSERIAL_H_