Need help in modifying read statement.

Projects Programming
1

I am trying to modify downloaded Arduino program. Right now it seems to read ASCII code corresponding to a keyboard key pressed. It has three options as shown. If I want the servo to turn its shaft say by 6 steps then I need to press appropriate keyboard key six times (in Serial Monitor window). What I want to do is to input an integer (in Serial Monitor window), say 57 and have the server move by corresponding numbers of steps (say each step = 1 degree, thus turning servo by 57 degrees). Right now if I wanted to rotate the shaft by one degree I would have to press the key 57 times. How do I change the read statement (or the program) to get needed result? I have limited programming skills.

Code
snip
25. int centerServo; // center servo position
26. int pulseWidth; // servo pulse width
27. int moveServo; // raw user input
28. long lastPulse = 0; // recorded time (ms) of the last pulse
29.
30.
31. void setup() {
32. pinMode(servoPin, OUTPUT); // Set servo pin as an output pin
33. centerServo = maxPulse - ((maxPulse - minPulse)/2);
34. pulseWidth = centerServo; // Give the servo a starting point (or it floats)
35. Serial.begin(9600);
36. Serial.println(" Arduino Serial Servo Control");
37. Serial.println("Press < or > to move, spacebar to center");
38. Serial.println();
39. }
40.
41. void loop() {
42. // wait for serial input
43. if (Serial.available() > 0) {
44. // read the incoming byte:
45. moveServo = Serial.read();
46.
47. // ASCII '<' is 44, ASCII '>' is 46 (comma and period, really)
48. if (moveServo == 44) { pulseWidth = pulseWidth - turnRate; }
49. if (moveServo == 46) { pulseWidth = pulseWidth + turnRate; }
50. if (moveServo == 32) { pulseWidth = centerServo; }
snip

2

Checkout asciitable.com

A simple way would be to read the tens character, subtract 0x30 to convert to a digit, read the ones character, subtract 0x30 to convert to a digit, then
result = tens_digit *10 + ones_digit;
or maybe three characters, or watch for a special character to indicate if only 1 digit is commanded, etc.

3

Right now it seems to read ASCII code corresponding to a keyboard key pressed.

Yes and that is what it will always do.

How do I change the read statement (or the program) to get needed result?

You don't change the read statement you change your program.
You have a while loop where you read in the data from the serial port.
For each byte you read you see if it is between 0x30 (ACSII 0) and 0x39 (ASCII 9), if it is you convert the ASCII to a decimal number by simply ANDing it with 0xf like this:-

number = ascii & 0xf;

Then add this number into the final number you are accumulating, remembering to multiply the previous number by 10.

finalNumber = (finalNumber * 10) + number;

If the byte is outside 0x30 (ACSII 0) and 0x39 (ASCII 9) then you either ignore it or you terminate your loop. If you ignore it then you need to look for a carriage return (ASCII 13) to terminate your loop.

I have limited programming skills.

So one way of unlimiting them is to try exercises like this. Just write a routine that does this and then prints out the number. If you get stuck then post it and people will help.

4
5

Thank you all.
Les