From add1624f97a2a67e36777defb9fd232b62162d14 Mon Sep 17 00:00:00 2001
From: Stephan Richter <s.richter@srsoftware.de>
Date: Mon, 13 Nov 2023 00:08:21 +0100
Subject: [PATCH] this does *not* work

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>
---
 SoftRS485.cpp                              | 220 +++++++++++++++------
 SoftRS485.h                                |   3 +-
 examples/ReceiveDemo/ReceiveDemo.ino       |   6 +-
 examples/SendAndReceive/SendAndReceive.ino |  18 +-
 4 files changed, 172 insertions(+), 75 deletions(-)

diff --git a/SoftRS485.cpp b/SoftRS485.cpp
index ca68918..3339dfb 100644
--- a/SoftRS485.cpp
+++ b/SoftRS485.cpp
@@ -7,11 +7,18 @@
 #include "SoftRS485.h"
 
 //#define DEBUG
+
 #define MSG_LEN 64
+#define IDLE 0
+#define WAIT 1
+#define SEND 2
+#define SENT 3
 
+#define TIMER 250
 // Pins
 int _RO, _RE, _DE, _DI;
-long _pulse_len = 100;
+long _pulse_len = 850;
+
 
 // Receive vars
 boolean _recv_bit = false;
@@ -21,6 +28,28 @@ int _recv_pos = 0;
 int _recv_idx = 0;
 boolean _avail = false;
 
+// Send vars
+char _send_message[MSG_LEN];
+int _send_state = IDLE;
+int _send_pos = 0;
+int _send_idx = 0;
+boolean _send_bit = false;
+
+void enableSendTimer(){
+#ifdef DEBUG
+    Serial.print(F("Enabling send timer. Old Value: b"));
+    Serial.println(TIMSK1,BIN);
+#endif
+    TIMSK1 |= B00000010;  // Enable Timer COMPA Interrupt
+}
+
+void disableSendTimer(){
+#ifdef DEBUG
+    Serial.println("Disable send timer");
+#endif
+    TIMSK1 = TIMSK1 & ~B00000010;  // Enable Timer COMPA Interrupt
+}
+
 void interrupt485(){
     _recv_bit = !digitalRead(_RO); // HIGH level = logical zero and vice versa
     long now = micros();
@@ -28,22 +57,36 @@ void interrupt485(){
     _last_flip = now;
     if (diff > 20*_pulse_len){ // we received a start bit
 #ifdef DEBUG
-        Serial.print(F("State changed to ")); Serial.println(_recv_bit);
         Serial.println(F("received start bit"));
 #endif
         _recv_pos = 0;
         _recv_idx = 0;
         _last_flip+=_pulse_len;
     } else {
+#ifdef DEBUG
+        Serial.print(diff);
+        Serial.println("µs");
+#endif
+
         long count = diff/_pulse_len;
         for (int i=0; i<count; i++){
+#ifdef DEBUG
+            Serial.print(_recv_bit);
+            Serial.println(" <=");
+#endif
             if (_recv_idx == 0) {
-                _recv_msg[_recv_pos] = (!_recv_bit);
+                _recv_msg[_recv_pos] = (_recv_bit);
             } else {
-                _recv_msg[_recv_pos] |= (!_recv_bit)<<_recv_idx;
+                _recv_msg[_recv_pos] |= (_recv_bit)<<_recv_idx;
             }
             _recv_idx++;
             if (_recv_idx == 8){
+#ifdef DEBUG
+                Serial.print("0x");
+                Serial.print(_recv_msg[_recv_pos],HEX);
+                Serial.print(" recevied / ");
+                Serial.println((char)_recv_msg[_recv_pos]);
+#endif
                 _recv_idx = 0;
                 if (_recv_msg[_recv_pos] == 0x00){
                     _avail = _recv_pos != 0;
@@ -55,6 +98,102 @@ void interrupt485(){
     }
 }
 
+ISR(TIMER1_COMPA_vect){
+    OCR1A += TIMER; // Advance The COMPA Register
+
+    boolean echo = digitalRead(_RO);
+
+    if (_send_state == SENT){
+        if (echo != _send_bit){
+            digitalWrite(_DE,LOW);
+            _send_state = WAIT;
+#ifdef DEBUG
+            Serial.println(F("Collision"));
+#endif
+        } else {
+            digitalWrite(_DE,LOW);
+            _send_message[0] = 0x00;
+            _send_state = IDLE;
+            disableSendTimer();
+#ifdef DEBUG
+            Serial.println(F("Transmission complete"));
+#endif
+        }
+        return;
+    }
+
+    if (_send_state == SEND){
+        if (echo != _send_bit){
+            digitalWrite(_DE,LOW);
+            _send_state = WAIT;
+    #ifdef DEBUG
+            Serial.println(F("Collision"));
+    #endif
+            return;
+        }
+
+        char c = _send_message[_send_pos];
+        _send_bit = c & (1 << _send_idx);
+        digitalWrite(_DI,_send_bit);
+
+#ifdef DEBUG
+        if (!_send_idx) {
+            Serial.print("Sending "); Serial.print(c); Serial.print(" / 0x"); Serial.println(c,HEX);
+        }
+        Serial.print("<--- "); Serial.println(_send_bit);
+#endif
+        _send_idx++;
+        if (_send_idx == 8) {
+            _send_idx = 0;
+            _send_pos++;
+            if (c == 0x00 || _send_pos == MSG_LEN){
+                _send_state = SENT;
+            }
+        }
+    }
+
+    if (_send_state == WAIT){
+        long diff = micros() - _last_flip; // µs
+        long idle_count = diff / _pulse_len;
+        if (idle_count > MSG_LEN){
+            _send_bit = LOW;
+            digitalWrite(_DE,HIGH);
+            digitalWrite(_DI,_send_bit);
+            _send_state = SEND;
+            _send_idx = 0;
+            _send_pos = 0;
+#ifdef DEBUG
+            Serial.println(F("Sending start bit (1)"));
+#endif
+        } else {
+#ifdef DEBUG
+            Serial.println(F("Bus busy"));
+#endif
+            return;
+        }
+    }
+
+    echo = digitalRead(_RO);
+    if (echo != _send_bit){
+        digitalWrite(_DE,LOW);
+        _send_state = WAIT;
+#ifdef DEBUG
+        Serial.println(F("Collision"));
+#endif
+        return;
+    }
+
+}
+
+void configureSendTimer(){
+    TCCR1A = 0;           // Init Timer1A
+    TCCR1B = 0;           // Init Timer1B
+    TCCR1B |= B00000011;  // Prescaler = 1
+    OCR1A = TIMER;        // Timer Compare1A Register
+}
+
+
+
 void init485(int RO, int nRE, int DE, int DI){
     _RO=RO;
     _RE=nRE;
@@ -73,7 +212,7 @@ void init485(int RO, int nRE, int DE, int DI){
     digitalWrite(_DI,LOW); // output line = LOW
 
     attachInterrupt(digitalPinToInterrupt(_RO),interrupt485,CHANGE);
-
+    configureSendTimer();
 #ifdef DEBUG
     Serial.begin(115200);
     Serial.print(F("RO = "));
@@ -88,15 +227,6 @@ void init485(int RO, int nRE, int DE, int DI){
     _last_flip = micros();
 }
 
-void speed485(long baudrate){
-#ifndef DEBUG
-    _pulse_len = 1e6 / baudrate;
-#else
-    _pulse_len = 1000;
-    Serial.print(F("Set pulse_len to ")); Serial.print(_pulse_len); Serial.println(F("µs"));
-#endif
-}
-
 boolean available485(){
     return _avail;
 }
@@ -106,59 +236,29 @@ String get485message(){
     return String((char*)_recv_msg);
 }
 
-boolean writeBit(boolean bit){
-    digitalWrite(_DI,!bit);
-    delayMicroseconds(5);
-    if (_recv_bit != bit){ // collision!
-       digitalWrite(_DE,LOW);
+
+boolean send485(String message){
+    if (_send_message[0] != 0x00) {
 #ifdef DEBUG
-       Serial.println(F("Collision!"));
+        Serial.println("Busy!");
 #endif
-       return false;
+        return false; // we already have a queued message, abort!
     }
-    delayMicroseconds(_pulse_len-5);
-    return true;
-}
 
-boolean send485(char message[]){
 #ifdef DEBUG
-    Serial.print(F("preparing to send "));
-    Serial.print(message);
-    Serial.print(F(": line state = "));
-    Serial.print(_recv_bit);
-    Serial.print(F(" / last_flip = "));
-    Serial.print(_last_flip);
-    Serial.print(F(" / micros = "));
-    Serial.println(micros());
+    Serial.print(F("Preparing to send ")); Serial.println(message);
 #endif
-    while (_recv_bit || (micros() - _last_flip) < (20 * _pulse_len)) {
-        delayMicroseconds(20*_pulse_len);
+    const char* buf = message.c_str();
+    for (int idx = 0; idx<MSG_LEN; idx++){
+        _send_message[idx] = buf[idx]; // copy message
+        if (_send_message[idx] == 0x00) break;
     }
+    if (_send_message[0] == 0x00) return false; // message is empty
 #ifdef DEBUG
-    Serial.println(F("enabling driver…"));
-#endif
-    digitalWrite(_DE,HIGH); // enable driver
-    if (!writeBit(HIGH)) return false;
-    int pos = -1;
-    boolean good = true;
-    do {
-        pos++;
-#ifdef DEBUG
-        Serial.print(F("sending character ")); Serial.println(message[pos]);
-#endif
-        good = writeBit(message[pos] & 0x01)
-            && writeBit(message[pos] & 0x02)
-            && writeBit(message[pos] & 0x04)
-            && writeBit(message[pos] & 0x08)
-            && writeBit(message[pos] & 0x10)
-            && writeBit(message[pos] & 0x20)
-            && writeBit(message[pos] & 0x40)
-            && writeBit(message[pos] & 0x80);
-    } while (good && message[pos]);
-    if (good) writeBit(1);
-    digitalWrite(_DE,LOW); // disable driver
-#ifdef DEBUG
-    Serial.println(F("disabled driver…"));
+    Serial.print(F("Message copied to send buffer: "));
+    Serial.println(_send_message);
 #endif
-    return good;
+    _send_state = WAIT;
+    enableSendTimer();
+    return true;
 }
diff --git a/SoftRS485.h b/SoftRS485.h
index daf9344..4b6b1cf 100644
--- a/SoftRS485.h
+++ b/SoftRS485.h
@@ -9,8 +9,7 @@
 #include "Arduino.h"
 
 extern void init485(int RO, int nRE, int DE, int DI);
-extern void speed485(long pulse_length);
 extern boolean available485();
 extern String get485message();
-extern boolean send485(char message[]);
+extern boolean send485(String message);
 #endif
diff --git a/examples/ReceiveDemo/ReceiveDemo.ino b/examples/ReceiveDemo/ReceiveDemo.ino
index 297b91d..9a77383 100644
--- a/examples/ReceiveDemo/ReceiveDemo.ino
+++ b/examples/ReceiveDemo/ReceiveDemo.ino
@@ -7,6 +7,7 @@
 
 void setup() {
   Serial.begin(115200);
+  Serial.println(F("This is ReceiveDemo, version 0.1"));
 
   init485(2,3,4,5); // library initialization:
   // connect pin 2 to RO of Max485
@@ -17,8 +18,5 @@ void setup() {
 }
 
 void loop(){
-  if (available485()){ // check if we have received anything
-    Serial.print("messageReceived: ");
-    Serial.println(get485Message()); // read the received message
-  }
+  if (available485()) Serial.println("Received: "+get485message());
 }
diff --git a/examples/SendAndReceive/SendAndReceive.ino b/examples/SendAndReceive/SendAndReceive.ino
index 5ad30b7..a7f6382 100644
--- a/examples/SendAndReceive/SendAndReceive.ino
+++ b/examples/SendAndReceive/SendAndReceive.ino
@@ -2,17 +2,17 @@
 
 void setup() {
   Serial.begin(115200);
-  init485(2,3,4,5);
-  speed485(8000);
-  boolean sent = false;
-  while (!sent) {
-    sent = send485("This message is sent and received!");
-  }
+  Serial.println("This is SendAndReceive 0.1");
+  init485(2,3,4,5); // library initialization:
+  // connect pin 2 to RO of Max485
+  // connect pin 3 to ^RE of Max485
+  // connect pin 4 to DE of Max485
+  // connect pin 5 to DI of Max485
+
+  while (send485("Hello World!")) {}
 }
 
 void loop() {
   // put your main code here, to run repeatedly:
-  if (available485()){
-    Serial.println("Received "+get485message());
-  }
+  if (available485()) Serial.println("Received "+get485message());
 }