danricho · January 1, 2021 05:04 · Jan 1, 2021
diff --git a/Arduino Python Comms b/Arduino Python Comms
@@ -0,0 +1 @@
+This is a simple communication scheme between python and Arduino over Serial.
diff --git a/arduino_comms.ino b/arduino_comms.ino
@@ -0,0 +1,116 @@
+int TO_RPI = 4;
+int FR_RPI = 5;
+
+// NON BLOCKING SERIAL!
+
+int millisSince(unsigned long start){
+  return (millis()-start);
+}
+
+void waitUntil(int millis, unsigned long start){
+  delay(millis - millisSince(start));
+}
+
+int headerFromMillis(int millis){
+  if ((millis > 85) || (millis < 15)){ return 0; }
+  else if ((millis > 15) && (millis < 25)) { return 1; }
+  else if ((millis > 35) && (millis < 45)) { return 2; }
+  else if ((millis > 55) && (millis < 65)) { return 3; }
+  else if ((millis > 75) && (millis < 85)) { return 4; }
+}
+
+void writeBit(bool state){
+  digitalWrite(4, LOW);
+  if (state){ delay(10); } else { delay(5); }
+  digitalWrite(4, HIGH);
+    if (state){ delay(5); } else { delay(10); }
+}
+
+int message = 1;
+long centiVolts;
+byte encodedVolts;
+
+void setup() {
+  pinMode(LED_BUILTIN, OUTPUT);
+  pinMode(TO_RPI, OUTPUT);
+  pinMode(FR_RPI, INPUT);
+}
+
+void loop() {
+
+  unsigned long loop_start = millis();
+
+  digitalWrite(LED_BUILTIN, HIGH);
+  digitalWrite(TO_RPI, LOW);
+  delay(20 * (message));
+  digitalWrite(TO_RPI, HIGH);
+
+  if (message == 1){
+    delay(20); // make sure RPi is ready
+    // STANDIN - will be a analogue read
+    centiVolts = random(0, 1000);
+    encodedVolts = map(centiVolts,0,1000,0,255);
+
+    // Serial.print("Data binary (big-endian): ");
+    for (byte mask = 00000001; mask>0; mask <<= 1){
+     if (encodedVolts & mask) {
+        // Serial.print("1");
+        writeBit(1);
+      } else {
+        // Serial.print("0");
+        writeBit(0);
+      }
+    }
+  }
+
+  Serial.print("Sent ");
+  Serial.print(message);
+  Serial.print(", Pulse Length: ");
+  Serial.print(20 * (message));
+  if (message == 1){
+    Serial.print(", Volts: ");
+    Serial.print(float(centiVolts)/100.0);
+    // Serial.print(", Data: ");
+    // Serial.print(encodedVolts);
+  }
+  Serial.println("");
+
+  digitalWrite(LED_BUILTIN, LOW);
+
+  waitUntil(950, loop_start);
+
+  int previous_state = digitalRead(FR_RPI);
+  int this_state;
+  unsigned long fall_start = 0;
+  unsigned long pulseLength = 0;
+  int header = 0;
+  while (millisSince(loop_start) < 1950){
+    this_state = digitalRead(FR_RPI);
+    if (fall_start == 0){
+      if (previous_state) {
+        if (!this_state) { // FALLING EDGE
+          fall_start = millis();
+        }
+      }
+    }
+    else {
+      if (this_state) { // RISING EDGE
+        pulseLength = millisSince(fall_start);
+        header = headerFromMillis(pulseLength);
+        break;
+      }
+    }
+  }
+
+  Serial.print("Got ");
+  Serial.print(header);
+  Serial.print(", Pulse Length: ");
+  Serial.print(pulseLength);
+  Serial.println("");
+  Serial.println("");
+
+  message = (message % 4) + 1;
+
+  waitUntil(2000, loop_start);
+
+}
diff --git a/rpi_resident.py b/rpi_resident.py
@@ -0,0 +1,72 @@
+import RPi.GPIO as GPIO
+from datetime import datetime
+import random
+import time
+import struct
+
+TO_RPI = 4
+FR_RPI = 5
+
+def myround(x, base=5):
+  return base * round(x/base)
+
+def delay(millis):
+  time.sleep(max(0,millis/1000))
+
+def millisSince(start):
+  return round((datetime.now() - start).microseconds / 100) / 10
+
+def waitUntil(millis, start):
+  delay(millis - millisSince(start));
+
+def headerFromMillis(millis):
+  if millis > 85 or millis < 15:
+    return None # NOT A MESSAGE TYPE HEADER - PROBABLY END OF DATA
+  else:
+    return round(myround(millis, 20) / 20)
+
+def getBit(pin):
+  GPIO.wait_for_edge(pin, GPIO.FALLING, timeout=1000)
+  rise = datetime.now()
+  GPIO.wait_for_edge(pin, GPIO.RISING, timeout=1000)
+  return round((datetime.now() - rise).microseconds / 100) / 10 > 7.5
+
+GPIO.setmode(GPIO.BCM)
+GPIO.setup(TO_RPI, GPIO.IN, pull_up_down=GPIO.PUD_UP)
+GPIO.setup(FR_RPI, GPIO.OUT)
+
+try:
+  while(1):
+    GPIO.wait_for_edge(TO_RPI, GPIO.FALLING, timeout=1000)
+    loop_start = datetime.now() # UPS SEND SYNC.
+    GPIO.wait_for_edge(TO_RPI, GPIO.RISING, timeout=1000)
+    pulseLength = millisSince(loop_start)
+    header = headerFromMillis(pulseLength)
+
+    if header:
+      voltage = None
+      if header == 1:
+        number = 0
+        for i in range(0,8):
+          number += (getBit(4) << i)
+        # print("Data binary (little-endian): {:08b}".format(number))
+        voltage = round(number / 255.0 * 1000) / 100.0
+        print("Got " + str(header) + ", Pulse Length: "  + str(pulseLength) + ", Volts: {:.2f}".format(voltage));
+      else:
+
+        print("Got " + str(header) + ", Pulse Length: "  + str(pulseLength));
+      waitUntil(1000, loop_start);
+
+      GPIO.output(FR_RPI, GPIO.LOW)
+      time.sleep(((header * 20))/1000)
+      GPIO.output(FR_RPI, GPIO.HIGH)
+
+      print("Sent " + str(header) + ", Pulse Length: "  + str(pulseLength));
+
+      print("")
+
+
+except KeyboardInterrupt:
+  None
+
+GPIO.cleanup()           # clean up GPIO on normal exit
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		This is a simple communication scheme between python and Arduino over Serial.
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