started BiDi (for bi-directional communication)

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

BiDi/BiDi.ino

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+/* RS 485-Implementierung, die sowohl Schreiben als auch Lesen kann */
+/* Basis für andere Projekte */
+
+#define BUTTON 2
+#define RECEIVE 3
+#define RECEIVE_ENABLE 4
+#define SEND 5
+#define SEND_ENABLE 6
+
+#define MAX_LEN 128
+
+void setup() {
+  // Buttons connected to analog input lines
+  pinMode(A0,INPUT_PULLUP);
+  pinMode(A1,INPUT_PULLUP);
+  pinMode(A2,INPUT_PULLUP);
+  pinMode(A3,INPUT_PULLUP);
+  pinMode(A4,INPUT_PULLUP);
+  pinMode(A5,INPUT_PULLUP);
+  pinMode(A6,INPUT_PULLUP);
+  pinMode(A7,INPUT_PULLUP);
+  // Currently, all buttons are also connected via a diode to an interruptable pin, to notify on input changes.
+  // This interruptable pin should be assgined to BUTTON
+  pinMode(BUTTON,INPUT_PULLUP);
+  attachInterrupt(digitalPinToInterrupt(BUTTON),button,FALLING); // interrupt for button change
+
+  // Set up pins for RS485 connection
+  pinMode(RECEIVE, INPUT);
+  pinMode(RECEIVE_ENABLE, OUTPUT);
+  pinMode(SEND, OUTPUT);
+  pinMode(SEND_ENABLE, OUTPUT);
+  attachInterrupt(digitalPinToInterrupt(RECEIVE),receive,CHANGE); // interrupt for incoming RS485 traffic
+  
+  reset485();
+  buttons = 0x0;
+}
+
+void button() {
+  buttons = 0xFF ^ (digitalRead(A7)<<7 | digitalRead(A6)<<6 | digitalRead(A5)<<5 | digitalRead(A4)<<4 | digitalRead(A3)<<3 | (!digitalRead(A2))<<2 | digitalRead(A1)<<1 | digitalRead(A0));  
+}
+
+void receive(){
+  bool received_bit = digitalRead(RECEIVE);
+  curr = micros();
+  duration = curr - last;
+  Serial.print("Input switched to ");
+  Serial.print(received_bit?"H":"L");  
+  Serial.print(" after ");
+  Serial.print(duration);
+  Serial.println(" ticks");
+  last = curr;
+  if (duration > MAX_TICKS) reset485();
+  received_bit = !received_bit; // received_bit is the current value, the duration of the previous value (=inverted) has been measured
+  duration /= BASE;
+  while (duration > 0){
+    byte_idx--;
+    recv |= received_bit<<byte_idx;
+    if (byte_idx == 0) {
+      msg[msg_idx] = recv;
+      msg_idx++;
+      byte_idx = 8;
+      if (recv == 0x00) message_received();
+    }
+    duration--;
+  }
+}
+
+void reset485(){
+  byte_idx = 8;
+  msg_idx = 0;
+  recv=0x0;
+}
+
+void message_received(){
+  for (int i=0; i<MAX_LEN; i++) message[i]=msg[i];
+  reset485();
+}
+
+void button_pressed(int i){
+  Serial.println("not implemented");
+}
+
+void loop(){
+  if (buttons>0){
+    for (int i=0; i<7; i++){
+      if (buttons & (1<<i)) button_pressed(i);     
+    }    
+  }
+  if (message[0] != 0x0){
+    Serial.print("Received '");
+    Serial.print(message);
+    Serial.println("'");    
+    message[0] = 0x0;
+  }
+}

ManualSend/ManualSend.ino

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+/*// This sketch allows manual setting of the RS485-connected pins via serial terminal commands
+
+Commands are:
+r+ – enable read mode (^RE ← LOW)
+r- – disable read mode (^RE ← HIGH)
+w+ – enable write mode (DE ← HIGH)
+w- – disable write mode (DE ← LOW)
+h  – send HIGH level on DI
+l  – send LOW level on DI
+
+//*/
+
+#if defined(ARDUINO_AVR_UNO)
+  #define RS485_RO 5
+  #define RS485_RE 4
+  #define RS485_DE 3
+  #define RS485_DI 2
+  #define BOARD "Arduino Uno"
+#endif
+#if defined(ARDUINO_AVR_NANO)
+  #define RS485_RO 3
+  #define RS485_RE 2
+  #define RS485_DE 4
+  #define RS485_DI 5
+  #define BOARD "Arduino Nano"
+#endif
+
+String command = "";
+bool doPrint = false;
+// the setup function runs once when you press reset or power the board
+void setup() {
+  // initialize digital pin LED_BUILTIN as an output.
+  pinMode(RS485_RO, INPUT);
+  pinMode(RS485_RE, OUTPUT);
+  pinMode(RS485_DE, OUTPUT);
+  pinMode(RS485_DI, OUTPUT);
+  digitalWrite(RS485_RE,LOW);
+  digitalWrite(RS485_DE,LOW);
+  digitalWrite(RS485_DI,LOW);
+  Serial.begin(115200);
+  Serial.println(F("this is Projekte/Arduino/MAX485/ManualSend"));
+  Serial.println(F("send any of the followning commands:"));
+  Serial.println(F("- r+ (enable read)\n- r- (disable read)\n- w+ (enable write)\n- w- (disable write)\n- h (for high)\n- l (for low)"));
+}
+
+// the loop function runs over and over again forever
+void loop() {
+  while (Serial.available()){
+    char inChar = (char)Serial.read();
+    if (inChar == '\n') {
+      process(command);
+      command = ""; 
+      doPrint = true;
+    } else {
+      command += inChar;
+    }
+  }
+  if (doPrint){
+    printState();
+    delay(1000);
+  }
+}
+
+void printState(){
+  Serial.print("RE = ");
+  Serial.print(1-digitalRead(RS485_RE));
+  Serial.print(", DE = ");
+  Serial.print(digitalRead(RS485_DE));
+  Serial.print(", DI = ");
+  Serial.print(digitalRead(RS485_DI));
+  Serial.print(", RO = ");
+  Serial.println(digitalRead(RS485_RO));
+}
+
+void process(String command){
+  Serial.print(F("received:"));
+  Serial.println(command);
+  if (command == "r+") digitalWrite(RS485_RE,LOW);
+  if (command == "r-") digitalWrite(RS485_RE,HIGH);
+  if (command == "w+") digitalWrite(RS485_DE,HIGH);
+  if (command == "w-") digitalWrite(RS485_DE,LOW);
+  if (command == "h") digitalWrite(RS485_DI,HIGH);
+  if (command == "l") digitalWrite(RS485_DI,LOW);
+  printState();
+}

ManualSend/Readme.md

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+Erkenntnisse:
+
+1. Wenn alle Treiber inaktiv sind, also bei allen Teilnehmer DI = Low ist, kommt vom RO ein High-Signal
+2. das High-Signal ist dominant, d.h. wenn mehrere Teilnehmer senden, und mindestens ein Teilnehmer eine 1 auf den Bus legt, erhalten alle am RO einen HIGH-Pegel