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--- en:iot-open:remotelab:sut:generalpurpose2:b7 [2020/05/17 15:30] – pczekalski
+++ en:iot-open:remotelab:sut:generalpurpose2:b7 [Unknown date] (current) – external edit (Unknown date) 127.0.0.1
@@ Line 8: / Line 8: @@
 === Prerequisites ===
-You need to understand how typical servomotor looks like and how it works.\\
+You need to understand how a typical servomotor looks like and how it works.\\
-The servo is controlled using predefined, precise PWM timing. Most servos share exactly the same model (0-180 degree servos), regardless of their size and power voltage. Classical, analogue servo frequency is 50Hz = 20ms period and duty cycle of the high signal is 1ms for 0deg and 2ms for 180deg. So changing the PWM duty cycle from 1ms to 2ms (5% to 10%) rotates servo. There is no need, however, to implement manually (still you can do) but you will use a predefined library instead of manually setting-up PWM. This brings features like range mapping to control servo logical way (i.e. providing angle, not duty cycle).\\
+The servo is controlled using predefined, precise PWM timing. Most servos share exactly the same model (0-180 degree servos), regardless of their size and power voltage. Classical, analogue servo frequency is 50Hz = 20ms period and duty cycle of the high signal is 1ms for 0deg and 2ms for 180deg. So changing the PWM duty cycle from 1ms to 2ms (5% to 10%) rotates servo. There is no need, however, to implement manually (still you can do it) but you will use a predefined library instead of manually setting up PWM. This brings features like range mapping to control servo logical way (i.e. providing angle, not duty cycle).\\
 The library is ''Servo.h''.
@@ Line 15: / Line 15: @@
 === Scenario ===
-In this scenario, you will rotate the servo to the 0 degrees, then 45, 90, 135 and 180 degrees counter wise, then 180, 90, 0, clockwise. Note - Arrow pointing left means servo is set to 0, pointing right is 180 degrees, and when 90 degrees, arrow points down.
+In this scenario, you will rotate the servo to 0 degrees, then 45, 90, 135 and 180 degrees counter wise, then 180, 90, 0, clockwise. Note - Arrow pointing left means servo is set to 0, pointing right is 180 degrees, and when 90 degrees, arrow points down.
-We use LCD to get feedback about requested servo angle and to compare it with the result, but please note, it is just for information only and is not necessary to implement servo rotation.
+We use LCD to get feedback about the requested servo angle and to compare it with the result, but please note, it is just for information only and is not necessary to implement servo rotation.
 <note warning>Please DO NOT use ''loop()'' to implement infinite servo rotation as it will wear out quickly and can even burn. Servo is NOT INTENDED to rotate as a motor. Instead, implement your code to run once or twice in the ''setup()'' function. You may reset the node to restart your code without the need to recompile.</note>
@@ Line 39: / Line 39: @@
 ...
 Servo servo;
+...
+</code>
+If you intend to implement your solution with rotation targets array, here is a hint on array declaration:
+<code c>
+...
+byte angles[] = {0,45,90,135,180,90,0};
 ...
 </code>
@@ Line 46: / Line 53: @@
 <code c>
 ...
-LiquidCrystal_I2C lcd(0x3F,20,4);   // set the LCD address to 0x3F for nodes 1 through 5, 8 and 9 for a 20 chars and 4 line display
+LiquidCrystal_I2C lcd(0x3F,20,4);   // set the LCD address to 0x3F for nodes 1 through 5,
+                                 //8 and 9 for a 20 chars and 4 line display
 //LiquidCrystal_I2C lcd(0x27,20,4); // for nodes 10 and 11 only!
 ...
@@ Line 58: / Line 66: @@
   lcd.backlight();
   lcd.home();
+  lcd.print("Starting");
+...
+  servo.attach(servoPin);
+  servo.write(0); // rotate to 0 degrees.
 ...
 </code>
+Setting servo to the desired angle is as simple as calling ''servo.write(angle);''. The default mapping is 0...180 degrees for micro servos we use here.
+\\
+If you implement your solution using rotation targets array, here is a hint on how to implement the ''for'' loop to iterate over an array:
+<code c>
+...
+  for(int i=0; i<sizeof(angles); i++)
+  {
+...
+</code>
+The ''sizeof'' operator above brings you an automated evaluation of the array size during compilation, thus if you add or remove an item(s) from the array in the declaration section, the loop will automatically change iteration scope, according to the new array size.
+<note tip>Give it at least 2s gap between setting subsequent rotation target for the servo. Otherwise, you may be unable to reliably observe results via video stream.</note>
 == Step 5 ==
-Keep ''loop()'' dummy, empty method not to overheat the servo or to wear out it's gears:
+Keep ''loop()'' dummy, empty method not to overheat the servo or to wear out its gears:
 <code c>
 ...
@@ Line 69: / Line 95: @@
 }
 </code>
-''bmp.readPressure()'' function returns air pressure in //Pa//. You must convert it //hPa//, dividing by 100.
-To convert float into the string with formatting use ''sprintf'' function:
-<code c>
-...
-  sprintf(buffer,"%4.2f hPa",pres);
-...
-  delay(5000);
-...
-</code>
-<note tip>''sprintf'' uses number of wildcards that are rendered with data. Refer to the c/c++ documentation on ''sprintf''. Here <code c>%4.2f</code> means: having float number render it to string using four digits before decimal point and two after it. Air pressure readings should be somewhere between 890 and 1060 hPa.\\
-''delay(time)'' is measured in milliseconds.</note>
 === Result validation ===
-Observe air pressure readings on the LCD. Note - small oscillations are natural - you can implement moving average (i.e. of 10 subsequent reads, FIFO model) to "flatten" readings.
+Observe the arrow rotating to the desired angle.

en/iot-open/remotelab/sut/generalpurpose2/b7.1589729431.txt.gz · Last modified: 2020/07/20 09:00 (external edit)