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Increased transmission speed #27

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4f86b2a
reorganize timer prescaling
DrDiettrich May 28, 2016
842f5f7
prescale/1024 for T1-T5
DrDiettrich May 28, 2016
85ad33a
add debug features for timing
DrDiettrich May 28, 2016
a1166ba
improve delay before interrupt forced by interrupt
DrDiettrich May 28, 2016
936acfe
more flexible retrigger interval
DrDiettrich May 28, 2016
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105 changes: 69 additions & 36 deletions AltSoftSerial.cpp
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Open in desktop
Original file line number Diff line number Diff line change
@@ -1,17 +1,17 @@
/* An Alternative Software Serial Library
* http://www.pjrc.com/teensy/td_libs_AltSoftSerial.html
* Copyright (c) 2014 PJRC.COM, LLC, Paul Stoffregen, paul@pjrc.com
*
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
Expand Down Expand Up @@ -40,6 +40,8 @@
/****************************************/

static uint16_t ticks_per_bit=0;
static uint16_t cycles_per_tick=0;
static uint16_t ticks_to_exit=1; //if prescale > 8
bool AltSoftSerial::timing_error=false;

static uint8_t rx_state;
Expand Down Expand Up @@ -67,39 +69,70 @@ static volatile uint8_t tx_buffer[TX_BUFFER_SIZE];

#define MAX_COUNTS_PER_BIT 6241 // 65536 / 10.5

void AltSoftSerial::init(uint32_t cycles_per_bit)
uint16_t AltSoftSerial::ticksPerBit()
{
//Serial.printf("cycles_per_bit = %d\n", cycles_per_bit);
if (cycles_per_bit < MAX_COUNTS_PER_BIT) {
return ticks_per_bit;
}
uint16_t AltSoftSerial::cyclesPerTick()
{
return cycles_per_tick;
}

bool AltSoftSerial::prescale(uint32_t cycles_per_bit)
{
timing_error = false;
ticks_per_bit = cycles_per_bit;
ticks_to_exit = 1;
if (ticks_per_bit < MAX_COUNTS_PER_BIT) {
//Serial.printf("cycles_per_bit = %d\n", cycles_per_bit);
cycles_per_tick = 1;
ticks_to_exit = 64;
CONFIG_TIMER_NOPRESCALE();
} else {
cycles_per_bit /= 8;
return true;
}
ticks_per_bit = cycles_per_bit / 8;
if (ticks_per_bit < MAX_COUNTS_PER_BIT) {
//Serial.printf("cycles_per_bit/8 = %d\n", cycles_per_bit);
if (cycles_per_bit < MAX_COUNTS_PER_BIT) {
CONFIG_TIMER_PRESCALE_8();
} else {
cycles_per_tick = 8;
ticks_to_exit = 8;
CONFIG_TIMER_PRESCALE_8();
return true;
}
#if defined(CONFIG_TIMER_PRESCALE_128)
ticks_per_bit = cycles_per_bit / 128;
if (ticks_per_bit < MAX_COUNTS_PER_BIT) {
//Serial.printf("cycles_per_bit/64 = %d\n", cycles_per_bit);
cycles_per_tick = 128;
CONFIG_TIMER_PRESCALE_128();
return true;
}
#endif
#if defined(CONFIG_TIMER_PRESCALE_256)
cycles_per_bit /= 32;
//Serial.printf("cycles_per_bit/256 = %d\n", cycles_per_bit);
if (cycles_per_bit < MAX_COUNTS_PER_BIT) {
CONFIG_TIMER_PRESCALE_256();
} else {
return; // baud rate too low for AltSoftSerial
}
#elif defined(CONFIG_TIMER_PRESCALE_128)
cycles_per_bit /= 16;
//Serial.printf("cycles_per_bit/128 = %d\n", cycles_per_bit);
if (cycles_per_bit < MAX_COUNTS_PER_BIT) {
CONFIG_TIMER_PRESCALE_128();
} else {
return; // baud rate too low for AltSoftSerial
}
#else
return; // baud rate too low for AltSoftSerial
ticks_per_bit = cycles_per_bit / 256;
if (ticks_per_bit < MAX_COUNTS_PER_BIT) {
//Serial.printf("cycles_per_bit/256 = %d\n", cycles_per_bit);
cycles_per_tick = 256;
CONFIG_TIMER_PRESCALE_256();
return true;
}
#endif
}
#if defined(CONFIG_TIMER_PRESCALE_1024)
ticks_per_bit = cycles_per_bit / 1024;
if (ticks_per_bit < MAX_COUNTS_PER_BIT) {
//Serial.printf("cycles_per_bit/1024 = %d\n", cycles_per_bit);
cycles_per_tick = 1024;
CONFIG_TIMER_PRESCALE_1024();
return true;
}
ticks_per_bit = cycles_per_bit;
#endif
timing_error = true;
//Serial.println("baudrate too low");
return false; //baudrate too low
}

bool AltSoftSerial::init(uint32_t cycles_per_bit)
{
if (!prescale(cycles_per_bit)) return false;
rx_stop_ticks = cycles_per_bit * 37 / 4;
pinMode(INPUT_CAPTURE_PIN, INPUT_PULLUP);
digitalWrite(OUTPUT_COMPARE_A_PIN, HIGH);
Expand All @@ -111,6 +144,7 @@ void AltSoftSerial::init(uint32_t cycles_per_bit)
tx_buffer_head = 0;
tx_buffer_tail = 0;
ENABLE_INT_INPUT_CAPTURE();
return true;
}

void AltSoftSerial::end(void)
Expand Down Expand Up @@ -174,10 +208,10 @@ ISR(COMPARE_A_INTERRUPT)
} else {
CONFIG_MATCH_CLEAR();
}
SET_COMPARE_A(target);
tx_bit = bit;
tx_byte = byte;
tx_state = state;
SET_COMPARE_A(target);
// TODO: how to detect timing_error?
return;
}
Expand All @@ -188,7 +222,7 @@ ISR(COMPARE_A_INTERRUPT)
if (state == 10) {
// Wait for final stop bit to finish
tx_state = 11;
SET_COMPARE_A(target + ticks_per_bit);
SET_COMPARE_A(target + ticks_per_bit + ticks_to_exit);
} else {
tx_state = 0;
CONFIG_MATCH_NORMAL();
Expand All @@ -199,12 +233,12 @@ ISR(COMPARE_A_INTERRUPT)
tx_buffer_tail = tail;
tx_byte = tx_buffer[tail];
tx_bit = 0;
tx_state = 1;
CONFIG_MATCH_CLEAR();
if (state == 10)
SET_COMPARE_A(target + ticks_per_bit);
SET_COMPARE_A(target + ticks_per_bit + ticks_to_exit);
else
SET_COMPARE_A(GET_TIMER_COUNT() + 16);
tx_state = 1;
SET_COMPARE_A(GET_TIMER_COUNT() + ticks_to_exit);
// TODO: how to detect timing_error?
}
}
Expand Down Expand Up @@ -347,4 +381,3 @@ void ftm0_isr(void)
if (flags & (1<<6) && (FTM0_C6SC & 0x40)) altss_compare_a_interrupt();
}
#endif

14 changes: 9 additions & 5 deletions AltSoftSerial.h
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,17 +1,17 @@
/* An Alternative Software Serial Library
* http://www.pjrc.com/teensy/td_libs_AltSoftSerial.html
* Copyright (c) 2014 PJRC.COM, LLC, Paul Stoffregen, paul@pjrc.com
*
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
Expand Down Expand Up @@ -44,7 +44,7 @@ class AltSoftSerial : public Stream
public:
AltSoftSerial() { }
~AltSoftSerial() { end(); }
static void begin(uint32_t baud) { init((ALTSS_BASE_FREQ + baud / 2) / baud); }
static bool begin(uint32_t baud) { return init((ALTSS_BASE_FREQ + baud / 2) / baud); }
static void end();
int peek();
int read();
Expand All @@ -67,9 +67,13 @@ class AltSoftSerial : public Stream
static int library_version() { return 1; }
static void enable_timer0(bool enable) { }
static bool timing_error;
//debug features
static uint16_t ticksPerBit();
static uint16_t cyclesPerTick();
private:
static void init(uint32_t cycles_per_bit);
static bool init(uint32_t cycles_per_bit);
static void writeByte(uint8_t byte);
static bool prescale(uint32_t cycles_per_bit);
};

#endif
10 changes: 7 additions & 3 deletions config/AltSoftSerial_Timers.h
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,17 +1,17 @@
/* An Alternative Software Serial Library
* http://www.pjrc.com/teensy/td_libs_AltSoftSerial.html
* Copyright (c) 2014 PJRC.COM, LLC, Paul Stoffregen, paul@pjrc.com
*
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
Expand All @@ -25,6 +25,7 @@
#define CONFIG_TIMER_NOPRESCALE() (TIMSK1 = 0, TCCR1A = 0, TCCR1B = (1<<ICNC1) | (1<<CS10))
#define CONFIG_TIMER_PRESCALE_8() (TIMSK1 = 0, TCCR1A = 0, TCCR1B = (1<<ICNC1) | (1<<CS11))
#define CONFIG_TIMER_PRESCALE_256() (TIMSK1 = 0, TCCR1A = 0, TCCR1B = (1<<ICNC1) | (1<<CS12))
#define CONFIG_TIMER_PRESCALE_1024() (TIMSK1 = 0, TCCR1A = 0, TCCR1B = (1<<ICNC1) | (1<<CS12)| (1<<CS10))
#define CONFIG_MATCH_NORMAL() (TCCR1A = TCCR1A & ~((1<<COM1A1) | (1<<COM1A0)))
#define CONFIG_MATCH_TOGGLE() (TCCR1A = (TCCR1A & ~(1<<COM1A1)) | (1<<COM1A0))
#define CONFIG_MATCH_CLEAR() (TCCR1A = (TCCR1A | (1<<COM1A1)) & ~(1<<COM1A0))
Expand Down Expand Up @@ -52,6 +53,7 @@
#define CONFIG_TIMER_NOPRESCALE() (TIMSK3 = 0, TCCR3A = 0, TCCR3B = (1<<ICNC3) | (1<<CS30))
#define CONFIG_TIMER_PRESCALE_8() (TIMSK3 = 0, TCCR3A = 0, TCCR3B = (1<<ICNC3) | (1<<CS31))
#define CONFIG_TIMER_PRESCALE_256() (TIMSK3 = 0, TCCR3A = 0, TCCR3B = (1<<ICNC3) | (1<<CS32))
#define CONFIG_TIMER_PRESCALE_1024() (TIMSK3 = 0, TCCR3A = 0, TCCR3B = (1<<ICNC3) | (1<<CS32) | (1<<CS30))
#define CONFIG_MATCH_NORMAL() (TCCR3A = TCCR3A & ~((1<<COM3A1) | (1<<COM3A0)))
#define CONFIG_MATCH_TOGGLE() (TCCR3A = (TCCR3A & ~(1<<COM3A1)) | (1<<COM3A0))
#define CONFIG_MATCH_CLEAR() (TCCR3A = (TCCR3A | (1<<COM3A1)) & ~(1<<COM3A0))
Expand Down Expand Up @@ -79,6 +81,7 @@
#define CONFIG_TIMER_NOPRESCALE() (TIMSK4 = 0, TCCR4A = 0, TCCR4B = (1<<ICNC4) | (1<<CS40))
#define CONFIG_TIMER_PRESCALE_8() (TIMSK4 = 0, TCCR4A = 0, TCCR4B = (1<<ICNC4) | (1<<CS41))
#define CONFIG_TIMER_PRESCALE_256() (TIMSK4 = 0, TCCR4A = 0, TCCR4B = (1<<ICNC4) | (1<<CS42))
#define CONFIG_TIMER_PRESCALE_1024() (TIMSK4 = 0, TCCR4A = 0, TCCR4B = (1<<ICNC4) | (1<<CS42) | (1<<CS40))
#define CONFIG_MATCH_NORMAL() (TCCR4A = TCCR4A & ~((1<<COM4A1) | (1<<COM4A0)))
#define CONFIG_MATCH_TOGGLE() (TCCR4A = (TCCR4A & ~(1<<COM4A1)) | (1<<COM4A0))
#define CONFIG_MATCH_CLEAR() (TCCR4A = (TCCR4A | (1<<COM4A1)) & ~(1<<COM4A0))
Expand Down Expand Up @@ -106,6 +109,7 @@
#define CONFIG_TIMER_NOPRESCALE() (TIMSK5 = 0, TCCR5A = 0, TCCR5B = (1<<ICNC5) | (1<<CS50))
#define CONFIG_TIMER_PRESCALE_8() (TIMSK5 = 0, TCCR5A = 0, TCCR5B = (1<<ICNC5) | (1<<CS51))
#define CONFIG_TIMER_PRESCALE_256() (TIMSK5 = 0, TCCR5A = 0, TCCR5B = (1<<ICNC5) | (1<<CS52))
#define CONFIG_TIMER_PRESCALE_1024() (TIMSK5 = 0, TCCR5A = 0, TCCR5B = (1<<ICNC5) | (1<<CS52) | (1<<CS50))
#define CONFIG_MATCH_NORMAL() (TCCR5A = TCCR5A & ~((1<<COM5A1) | (1<<COM5A0)))
#define CONFIG_MATCH_TOGGLE() (TCCR5A = (TCCR5A & ~(1<<COM5A1)) | (1<<COM5A0))
#define CONFIG_MATCH_CLEAR() (TCCR5A = (TCCR5A | (1<<COM5A1)) & ~(1<<COM5A0))
Expand Down