analog read a value and call it something else

Hi Randy,

Your code is close, but there are some basic rules that need to be understood, about operators, assignment and functions. Without this knowledge, you'll be repeatedly stuck.

Fortunately it doesn't take long to pick it up, and the best way is to look at some examples, and also study the Foundations section on the Arduino site.

When you're using specific functions from existing Arduino libraries, you can use the reference section to look up the specific function, to see if it has a

return value.

In your specific code, the second line doesn't make sense because the analogRead function provides a return value and you're choosing not to do anything with it in that second line.

Your first line already stores the analog value in a variable.

I've also included a link on C operators below, because while the Arduino website is good, in some areas it is slack.

Useful links:

Arduino - FunctionDeclaration

Arduino - Foundations

http://arduino.cc/en/Guide/HomePage

Arduino - AnalogRead

C - Operators

Hi shabaz, thanks for your reply. I have read all of those Arduino pages several times. Thats how I got this far, which might not seem very far. I understand about the second line just taking up space (thank you). This is for a motorcycle air ride suspension. When I get the right height, I want to commit it to progairState, or programmed air state. Then upon start up I will have the Arduino output to the compressor until airState equals progairstate. This is the programming part where I have the bike at the desired height, and want to store that value. I am hesitant to use progairState = airState, because airState will be changing, where I want progairState to be my target. I thought I read the Serial.println writes it as a variable to be used as a static number. I have been reading so much, I am confusing myself.

  airState = analogRead(airPin);

  if (airState != 0)                                 //ensure I have an input on A0

  Serial.println(progairState);           //save current reading as a static number to compare to elsewhere in code.

Hi Randy,

println is a function (aka member function) of the object called Serial. The println function is responsible for sending content over a serial port (this would be described in the Arduino Serial reference [link]). The function doesn't perform variable assignment. When you say "write to a variable" you mean "assignment". Assignment is done using an '=' operator.

This is the reason for all the links. Much like any language that may have verbs adjectives and punctuation, C and C++ (which is what the Arduino language is like) has functions, operators and so on. Recognising them comes over time, so it is important to spend time reading the theory and doing simple examples before moving on to building your own application.

Recognising them comes over time

Thats why I was just looking for an answer.

I get the whole learn by doing it yourself thing. When someone is stuck and confused, they just need to get past it and let that part sink in. I know I will learn by searching and reading. I have read so much, I am confused. I will look elsewhere.

Thank you for your time, adown

Randy Ashdown wrote:

I am hesitant to use progairState = airState, because airState will be changing, where I want progairState to be my target.

I think I now understand the confusion.

When an assignment is made, it is not forever, it is just for that point in time when the machine (the arduino) processes the instruction. Once the instruction has been processed, the Arduino forgets about it, just the memory

(where the variable contents are stored) is kept. It is not like algebra where y=mx means that y changes whenever m and/or x changes.

Once the assignment is made, the right side variable (airState) can be changed by you at any time, and it will not affect the left side variable.

In a similar vein, when you have a function providing the value for the assignment such as:

airState = analogRead(airPin);

The analog value is captured into airState just when the line is executed; they actual physical voltage on the pin can vary, but the left side variable (airState) won't change unless you execute the same line again at some stage (e.g. in a loop).

I spent some time coming to grips with various bits of Arduino.

Not coming from a software base, it was a struggle, but eventually it does sink in ..

You may want to look at this book.

http://it-ebooks.info/book/1982/

I found it different from many others in that it tackles it from the problem end.

Mark

I had never thought about it, but I can see that operators may look like an equation, which in the math world would always be valid, whereas with computers is not an equation and is just an instruction to be executed once.

I learned a lot from some kids books that showed how a computer worked, but probably these types of books are no longer written, nor geared for Arduino.

I had never thought about it, but I can see that operators may look like an equation, which in the math world would always be valid, whereas with computers is not an equation and is just an instruction to be executed once.

I learned a lot from some kids books that showed how a computer worked, but probably these types of books are no longer written, nor geared for Arduino.

@shabaz

If you were brought up on software, then some of the things seem normal.

For anyone that ventres into this world, then you have to learn both bits.

I found many examples don't use the same variables and you are constantly trying to think what xyz is, while understanding how its being used, and how that fits with what you want to do.

I can only suggest doing many examples and modifying them so you gain your own understanding (ie in your own terms) of what is happening.

There is a lot of information out there, but filtering the noise out sometimes is difficult.

Mark

I see the Z80 and 6502 mentioned. I used to love to program on the 6502. It was all hex programming since there was no easy higher language for it at that time. (late 50s-early 60s). Games were a big thing. Then Microsoft and IBM came along and changed all that. Good to reminisce a little.

Thanks