From 836ffa16cf56bd2988f8e86ee5f77a8e7ae060b6 Mon Sep 17 00:00:00 2001
From: Joshua Saxby <Joshua2.Saxby@live.uwe.ac.uk>
Date: Mon, 9 Mar 2020 12:57:26 +0000
Subject: [PATCH] Appeared to have eliminated bit-slip errors
---
source/ManchesterDecoder.cpp | 7 ++++
source/ManchesterDecoder.hpp | 5 +++
source/main.cpp | 79 ++++++++++++++++++++----------------
3 files changed, 57 insertions(+), 34 deletions(-)
diff --git a/source/ManchesterDecoder.cpp b/source/ManchesterDecoder.cpp
index 365c721..50a0bea 100644
--- a/source/ManchesterDecoder.cpp
+++ b/source/ManchesterDecoder.cpp
@@ -54,4 +54,11 @@ namespace com_saxbophone {
this->buffer.shrink_from_front(1);
return true;
}
+
+ void ManchesterDecoder::clear() {
+ this->buffer.clear();
+ // also reset state variables
+ this->symbol_index = 0;
+ this->current_byte = 0x00u;
+ }
};
diff --git a/source/ManchesterDecoder.hpp b/source/ManchesterDecoder.hpp
index 0e10408..55e770e 100644
--- a/source/ManchesterDecoder.hpp
+++ b/source/ManchesterDecoder.hpp
@@ -55,6 +55,11 @@ namespace com_saxbophone {
* @returns false if no bytes are available yet (destination is ignored)
*/
bool get_next_byte(uint8_t& destination);
+
+ /**
+ * @brief Clears the input buffer, in case you want to do that.
+ */
+ void clear();
private:
/**
* @brief Counter tracking how many "symbols" (i.e. boolean input states)
diff --git a/source/main.cpp b/source/main.cpp
index ba49722..14451b9 100644
--- a/source/main.cpp
+++ b/source/main.cpp
@@ -51,7 +51,7 @@ MicroBit ubit;
* @warn This method blocks until exactly one of button A or B is pressed!
*/
Role get_my_role() {
- ubit.serial.send("get_my_role()");
+ // ubit.serial.send("get_my_role()");
// scroll some stuff on the screen to prompt the user to choose
ubit.display.scroll("<M"); // point left to Button A to choose Master
ubit.sleep(100); // a brief pause
@@ -108,18 +108,24 @@ public:
*/
void barrier() {
// TODO: consider allowing for a ±10% margin of error
- unsigned long time_now = ubit.systemTime(); // what time is it now?
+ unsigned long start_time = ubit.systemTime(); // what time is it now?
// this is how much time we have left to next sync point
unsigned long time_left = TransceiverConfig::TRANSMISSION_WINDOW - (
- (time_now - this->synchronisation_timestamp) %
+ (start_time - this->synchronisation_timestamp) %
TransceiverConfig::TRANSMISSION_WINDOW
);
+ // calculate the time of the next sync point
+ unsigned long sync_point = start_time + time_left;
/*
* systemTime() can only sleep to 6ms resolution, so sleep to the nearest
* multiple of 6ms, rounded down
*/
ubit.sleep((time_left / 6) * 6);
- // TODO: consider adding busy-wait loop to increase accuracy
+ // busy wait loop sleeps for remainder of time
+ unsigned long time_now;
+ do {
+ time_now = ubit.systemTime();
+ } while (time_now < sync_point);
}
private:
@@ -137,7 +143,7 @@ private:
* been configured with a pin that can't do Digital I/O. In either
* case, this is a failure condition.
*/
- ubit.serial.send("MICROBIT_NOT_SUPPORTED\r\n");
+ // ubit.serial.send("MICROBIT_NOT_SUPPORTED\r\n");
return 2;
}
// successful execution continues here
@@ -146,7 +152,7 @@ private:
this->busy_wait_on_pin(0, 500, pin_state, start_time, end_time);
// check to make sure we didn't break out of the loop because of HI pin
if (pin_state != 0) {
- ubit.serial.send("Other Master on Line\r\n");
+ // ubit.serial.send("Other Master on Line\r\n");
return 4;
}
// there's definitely no-one else transmitting on the line, now we transmit
@@ -157,24 +163,24 @@ private:
this->busy_wait_on_pin(0, 200, pin_state, start_time, end_time);
// this time, check that the pin is HI --it must be HI, otherwise timeout
if (pin_state != 1) {
- ubit.serial.send("Timeout waiting for Slave\r\n");
+ // ubit.serial.send("Timeout waiting for Slave\r\n");
return 6;
}
- ubit.serial.printf("Slave Latency: %i\r\n", end_time - start_time);
+ // ubit.serial.printf("Slave Latency: %i\r\n", end_time - start_time);
// now, Slave should keep the Line HI for at least 400ms
this->busy_wait_on_pin(1, 400, pin_state, start_time, end_time);
// if the pin is LO, then Slave didn't drive it long enough
- ubit.serial.printf("Slave Reply: %i\r\n", end_time - start_time);
+ // ubit.serial.printf("Slave Reply: %i\r\n", end_time - start_time);
if (pin_state == 0) {
- ubit.serial.send("Slave Reply too SHORT\r\n");
+ // ubit.serial.send("Slave Reply too SHORT\r\n");
return 8;
}
// otherwise, pin is still HI --allow Slave up to 200ms to bring it LO
this->busy_wait_on_pin(1, 200, pin_state, start_time, end_time);
- ubit.serial.printf("Slave Reply: %i\r\n", end_time - start_time);
+ // ubit.serial.printf("Slave Reply: %i\r\n", end_time - start_time);
// if the pin is still HI, then Slave drove the pin for too long
if (pin_state == 1) {
- ubit.serial.send("Slave Reply too LONG\r\n");
+ // ubit.serial.send("Slave Reply too LONG\r\n");
return 10;
}
// otherwise, all we need to do now is to wait for synchronisation
@@ -185,7 +191,7 @@ private:
// check the pin can read digital values
int pin_state = ubit.io.pin[COMMS_PIN_NUMBER].getDigitalValue();
if (pin_state == MICROBIT_NOT_SUPPORTED) {
- ubit.serial.send("MICROBIT_NOT_SUPPORTED\r\n");
+ // ubit.serial.send("MICROBIT_NOT_SUPPORTED\r\n");
return 1;
} // oh no, it can't
// otherwise, it can read digital values
@@ -194,23 +200,23 @@ private:
this->busy_wait_on_pin(0, 10000, pin_state, start_time, end_time);
// clarify the loop ended because pin is now indeed HI
if (pin_state != 1) {
- ubit.serial.send("Timeout waiting for Master\r\n");
+ // ubit.serial.send("Timeout waiting for Master\r\n");
return 3;
} // we timed out
// otherwise, line is HI, wait for it to stay that way at least 400ms
this->busy_wait_on_pin(1, 400, pin_state, start_time, end_time);
- ubit.serial.printf("Master Probe: %i\r\n", end_time - start_time);
+ // ubit.serial.printf("Master Probe: %i\r\n", end_time - start_time);
// clarify the loop ended because timeout occurred (pin should be HI)
if (pin_state != 1) {
- ubit.serial.send("Master Probe too SHORT\r\n");
+ // ubit.serial.send("Master Probe too SHORT\r\n");
return 5;
} // pin went LO, that's not correct
// wait up to 200 more ms for line to go LO
this->busy_wait_on_pin(1, 200, pin_state, start_time, end_time);
- ubit.serial.printf("Master Probe: %i\r\n", end_time - start_time);
+ // ubit.serial.printf("Master Probe: %i\r\n", end_time - start_time);
// if line is still HI, then it's overrun
if (pin_state == 1) {
- ubit.serial.send("Master Probe too LONG\r\n");
+ // ubit.serial.send("Master Probe too LONG\r\n");
return 7;
}
// otherwise, it's now our turn to bring the line HI
@@ -304,7 +310,7 @@ private:
int await_synchronisation() {
// calculate synchronisation time and check it's in the future
unsigned long sync_time = this->synchronisation_timestamp + 2500;
- ubit.serial.printf("Sync Stamp: %i\r\n", sync_time);
+ // ubit.serial.printf("Sync Stamp: %i\r\n", sync_time);
unsigned long now_time = ubit.systemTime();
if (sync_time < now_time) return 11; // can't do it, sync point in past
// busy wait loop to wait until synchronisation time is reached
@@ -491,14 +497,19 @@ public:
* @brief Event-handler for input pin pulse HI or LO events
*/
void on_pulse(MicroBitEvent e) {
- // only act on pulses which are shorter than a certain duration
- if (e.timestamp > TransceiverConfig::MAXIMUM_PULSE_DURATION) return;
// create a new Pulse and store it in the buffer
Pulse p = {
e.value == MICROBIT_PIN_EVT_PULSE_LO ? false : true, // state
e.timestamp // duration
};
- ubit.serial.printf("on_pulse() -> { %i, %lu, }\r\n", p.state, p.duration);
+ // if it's a long silence, this is a good time to clear input buffer
+ if (p.state == false and p.duration > TransceiverConfig::MAXIMUM_PULSE_DURATION) {
+ this->decoder.clear(); // this helps mitigate bit-slip errors persisting
+ // ubit.serial.send("Clear Buffer\r\n");
+ }
+ // otherwise only act on pulses which are shorter than a certain duration
+ if (p.duration > TransceiverConfig::MAXIMUM_PULSE_DURATION) return;
+ // ubit.serial.printf("on_pulse() -> { %i, %lu, }\r\n", p.state, p.duration);
this->buffer.add(p);
}
@@ -523,7 +534,7 @@ public:
) {
// send two inputs of the given state
has_output = true;
- ubit.serial.printf("%d%d", p.state, p.state);
+ // ubit.serial.printf("%d%d", p.state, p.state);
this->decoder.input(p.state);
this->decoder.input(p.state);
} else if (
@@ -535,12 +546,12 @@ public:
) {
// send just one input of the given state
has_output = true;
- ubit.serial.printf("%d", p.state);
+ // ubit.serial.printf("%d", p.state);
this->decoder.input(p.state);
}
}
if (has_output) {
- ubit.serial.send("<- MANCHEDECODE in\r\n");
+ // ubit.serial.send("<- MANCHEDECODE in\r\n");
}
// empty the buffer
this->buffer.clear();
@@ -648,7 +659,7 @@ void morse_checker() {
* NOTE: for now, just sending characters as-is but in the future
* they will be encoded rather than sent raw
*/
- ubit.serial.printf("Morse Input: %d\r\n", (int)current);
+ // ubit.serial.printf("Morse Input: %c\r\n", current);
manchester_encoder.input(current); // NOTE: Might need cast
ubit.display.clear();
} else {
@@ -672,11 +683,11 @@ void flush_output() {
bool printed = false;
while (manchester_encoder.get_next_state(next_state)) {
printed = true;
- ubit.serial.printf("%i", next_state);
+ // ubit.serial.printf("%i", next_state);
line_driver.input(next_state);
}
if (printed) {
- ubit.serial.send(" <- MANCHECODE out\r\n");
+ // ubit.serial.send(" <- MANCHECODE out\r\n");
}
}
}
@@ -720,11 +731,11 @@ int main() {
// for now, we only act on button presses if we're the Master
if (my_role == Role::MASTER) {
// scroll "PM" to mean "PAIRED MASTER"
- ubit.serial.send(" -> Role::MASTER\r\n");
+ // ubit.serial.send(" -> Role::MASTER\r\n");
ubit.display.scroll("PM");
} else if (my_role == Role::SLAVE) {
// scroll "PS" to mean "PAIRED SLAVE"
- ubit.serial.send(" -> Role::SLAVE\r\n");
+ // ubit.serial.send(" -> Role::SLAVE\r\n");
ubit.display.scroll("PS");
}
@@ -750,13 +761,13 @@ int main() {
line_monitor.init();
while (true) { // TODO: consider what exit conditions can be used
// call barrier to synchronise both master and slave
- // pairer.barrier();
- ubit.sleep(10);
+ pairer.barrier();
// TODO: display the output?
uint8_t next_byte = 0x00u;
if (manchester_decoder.get_next_byte(next_byte)) {
- ubit.serial.printf("MANCHEDECODE -> %d\r\n", (int)next_byte);
- ubit.display.printCharAsync(next_byte, 500);
+ // ubit.serial.printf("MANCHEDECODE -> %c\r\n", next_byte);
+ ubit.display.printChar(next_byte, 300);
+ ubit.display.clear();
}
}
}
--
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