From c595bd2a151f69710bb1a4a61c839c3ea16bbfc0 Mon Sep 17 00:00:00 2001
From: Joshua Saxby <joshua.a.saxby@gmail.com>
Date: Sun, 8 Mar 2020 20:48:49 +0000
Subject: [PATCH] Rewrote some stuff and modified, pulling together
transmission code
---
source/ManchesterEncoder.cpp | 27 ++++++--------
source/ManchesterEncoder.hpp | 16 ++++----
source/main.cpp | 45 +++++++++++++++++++++--
tests/manchester_encoder_decoder_test.cpp | 6 ++-
4 files changed, 63 insertions(+), 31 deletions(-)
diff --git a/source/ManchesterEncoder.cpp b/source/ManchesterEncoder.cpp
index 411d61c..1e596ac 100644
--- a/source/ManchesterEncoder.cpp
+++ b/source/ManchesterEncoder.cpp
@@ -26,36 +26,31 @@ namespace com_saxbophone {
ManchesterEncoder::ManchesterEncoder()
: clock(true) // our implementation has the clock signal starting HI
, bit_index(0) // we definitely want to start reading bit 0
- , current_byte(0x00u)
{}
bool ManchesterEncoder::input(uint8_t byte) {
return this->buffer.add(byte); // buffer will return false if it's full
}
- int ManchesterEncoder::get_next_state() {
- // if we are at the start of a new byte
- if (this->clock == true and this->bit_index == 0) {
- // retrieve the next byte to encode and store in current_byte
- if (not this->buffer.is_empty()) {
- // use the buffer head and remove it from buffer
- this->current_byte = this->buffer[0];
- this->buffer.shrink_from_front(1);
- } else {
- // use the placeholder byte 0x00 so it has something to encode
- this->current_byte = 0x00u;
- }
- }
+ bool ManchesterEncoder::get_next_state(int& destination) {
+ // guard condition --check if buffer has content
+ if (this->buffer.is_empty()) return false;
// Manchester Code = Clock XOR Data
int symbol = this->clock xor this->extract_bit(
- this->current_byte,
+ this->buffer[0],
this->bit_index
);
+ destination = symbol;
+ // if we are at the end of a byte
+ if (this->clock == false and this->bit_index == 7) {
+ // shrink the buffer from the front by 1 to advance the buffer
+ this->buffer.shrink_from_front(1);
+ }
// update bit index whenever clock is LOW (end of duration of 1 data bit)
if (not this->clock) this->bit_index = (this->bit_index + 1u) % 8u;
// update clock every time
this->clock = not this->clock;
- return symbol;
+ return true;
}
bool ManchesterEncoder::extract_bit(uint8_t byte, uint8_t bit_index) const {
diff --git a/source/ManchesterEncoder.hpp b/source/ManchesterEncoder.hpp
index 8c5c6cc..c73543d 100644
--- a/source/ManchesterEncoder.hpp
+++ b/source/ManchesterEncoder.hpp
@@ -48,16 +48,14 @@ namespace com_saxbophone {
bool input(uint8_t byte);
/**
- * @returns the next state that the encoder wants the output line to
- * be set to, where 0 = LOW and 1 = HIGH
- * @note the encoder never runs out of input to output --if the buffer
- * becomes empty, the encoder outputs a Manchester Code sequence
- * equivalent to byte 0x00
- * @warn a side effect of this method is that it advances the internal
- * state of the encoder such that the next call will return the next bit
- * therefore multiple calls are not idempotent.
+ * @brief retrieves the next state that the encoder wants the output
+ * line to be set to, where 0 = LOW and 1 = HIGH, stores it in
+ * `destination`.
+ * @param destination[out] the int to write the next state to
+ * @returns true if there was a state available and it was stored
+ * @returns false if no states are available yet (destination is ignored)
*/
- int get_next_state();
+ bool get_next_state(int& destination);
private:
/**
* @brief Extracts the bit at given index from the given byte
diff --git a/source/main.cpp b/source/main.cpp
index 921c858..1562b40 100644
--- a/source/main.cpp
+++ b/source/main.cpp
@@ -21,6 +21,8 @@
#include "MicroBit.h"
+#include "ManchesterDecoder.hpp"
+#include "ManchesterEncoder.hpp"
#include "MorseDecoder.hpp"
#include "MorseEncoder.hpp"
#include "Pulse.hpp"
@@ -576,7 +578,7 @@ class LineDriver {
// STOP BIT
ubit.io.pin[COMMS_PIN_NUMBER].setDigitalValue(1);
ubit.sleep(TransceiverConfig::STOP_START_BIT_DURATION_MS);
- // drive low then switch to input
+ // drive low then switch to input mode
ubit.io.pin[COMMS_PIN_NUMBER].setDigitalValue(0);
ubit.io.pin[COMMS_PIN_NUMBER].getDigitalValue();
// remove transmitted bits
@@ -591,7 +593,15 @@ private:
// this will track the button presses
ButtonTracker button_tracker;
// this is used to encode bytes we want to send to go out on the line
-Transceiver transceiver;
+ManchesterEncoder manchester_encoder;
+// this switches the line state
+LineDriver line_driver;
+// this is used to decode bytes from the line
+ManchesterDecoder manchester_decoder;
+// this monitors the line for changes
+LineMonitor line_monitor(manchester_decoder);
+
+
// flag used by the morse_checker() fiber function to check if it should run
bool morse_checker_enabled = false;
@@ -614,7 +624,7 @@ void morse_checker() {
* NOTE: for now, just sending characters as-is but in the future
* they will be encoded rather than sent raw
*/
- transceiver.send(current); // NOTE: Might need cast
+ manchester_encoder.input(current); // NOTE: Might need cast
} else {
// otherwise, peek into what the code appears to be thus far
char peek = morse_decoder.peek();
@@ -628,6 +638,27 @@ void morse_checker() {
}
+// simple fiber that simply passes data out of encoder and into the line driver
+void flush_output() {
+ while (true) {
+ ubit.sleep(100); // yield the CPU for a bit
+ int next_state = 0;
+ while (manchester_encoder.get_next_state(next_state)) {
+ line_driver.input(next_state);
+ }
+ }
+}
+
+
+// simple fiber that simply flushes data out of line monitor and into decoder
+void flush_input() {
+ while (true) {
+ ubit.sleep(100); // yield the CPU for a bit
+ line_monitor.flush();
+ }
+}
+
+
int main() {
// Initialise the micro:bit runtime.
ubit.init();
@@ -636,7 +667,10 @@ int main() {
ubit.display.setDisplayMode(DISPLAY_MODE_GREYSCALE);
// create one fiber --this infinitely checks the decoder and outputs changes
- // create_fiber(morse_checker);
+ create_fiber(morse_checker);
+ // these lightweight fibers ferry data to and from decoders and line stuff
+ create_fiber(flush_output);
+ create_fiber(flush_input);
// this is the main program loop, an infinite while!
while (true) {
@@ -672,11 +706,14 @@ int main() {
while (true) { // TODO: consider what exit conditions can be used
// call barrier to synchronise both master and slave
pairer.barrier();
+ // flush the line driver
+ line_driver.flush();
}
} else { // Slave's comms loop
while (true) { // TODO: consider what exit conditions can be used
// call barrier to synchronise both master and slave
pairer.barrier();
+ // TODO: display the output?
}
}
diff --git a/tests/manchester_encoder_decoder_test.cpp b/tests/manchester_encoder_decoder_test.cpp
index 1a12dff..c6d6ca0 100644
--- a/tests/manchester_encoder_decoder_test.cpp
+++ b/tests/manchester_encoder_decoder_test.cpp
@@ -39,7 +39,8 @@ int main() {
printf("\n");
printf("Actual: \t");
for (size_t i = 0; i < 16; i++) {
- int state = encoder.get_next_state();
+ int state = 0;
+ encoder.get_next_state(state);
assert(state == t.output[i]);
decoder.input(state);
printf("%u", state);
@@ -63,7 +64,8 @@ int main() {
printf("%02x -> ", b);
encoder.input(b);
for (uint8_t i = 0; i < 16; i++) {
- int symbol = encoder.get_next_state();
+ int symbol;
+ encoder.get_next_state(symbol);
printf("%d", symbol);
decoder.input(symbol);
}
--
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