Maple Language Reference — Maple v0.0.11 Documentation

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# Maple Language Reference

The Maple can be programmed in the Wiring language, which is the same language used to program the Arduino boards.

C or C++ programmers curious about the differences between the Wiring language and C++ may wish to skip to the Note for C/C++ Hackers.

Contents

- Maple Language Reference
- `ASSERT(...)`
- Missing Arduino Features
- Unimplemented Arduino Features
- C++ for Maple
- Note for C/C++ Hackers
- Recommended Reading

Looking for Something Else?

- See the Maple Library Reference for extra built-in libraries for dealing with different kinds of hardware.
- If you’re looking for something from the C standard library (like `atoi()`, for instance): the CodeSourcery GCC compiler used to compile your programs is configured to link against newlib, and allows the use of any of its header files. However, dynamic memory allocation (`malloc()`, etc.) is not available.
- If you’re looking for pointers to low-level details, see this page’s Recommended Reading.

## Maple Language Reference

The following table summarizes the most important core language features. An exhaustive index is available at the Complete Language Index.

Structure | Variables | Functions
--- | --- | ---

- setup()
- loop()

Control Structures

- if/else
- for
- switch/case
- while
- do...while
- break
- continue
- return
- goto

Further syntax

- ; (semicolon)
- {} (curly braces)
- // (single-line comment)
- /* */ (multi-line comment)
- #define
- #include

Arithmetic Operators

- = (assignment)
- + (addition)
- - (subtraction)
- * (multiplication)
- / (division)
- % (modulo)

Comparison Operators

- == (equal to)
- != (not equal to)
- < (less than)
- > (greater than)
- <= (less than or equal to)
- >= (greater than or equal to)

Boolean Operators

- && (and)
- || (or)
- ! (not)

Pointer Operators

- * dereference operator
- & reference operator

Bitwise Operators

- & (bitwise and)
- | (bitwise or)
- ^ (bitwise xor)
- ~ (bitwise not)
- << (shift left)
- >> (shift right)

Compound Operators

- ++ (increment)
- - - (decrement)
- += (compound add)
- -= (compound subtract)
- *= (compound multiply)
- /= (compound divide)
- &= (compound bitwise and)
- |= (compound bitwise or)

Keywords

- C++ Keywords

Constants

- HIGH | LOW
- INPUT | OUTPUT
- true | false
- Constants (integers, floating point)
- Board-specific values

Data Types

> The size of each datatype, in bytes, is given in parentheses where appropriate.

> Note: The `word` type is (deliberately) not supported.

- void
- boolean (1 byte)
- char (1 byte)
- unsigned char (1 byte)
- byte (1 byte)
- int (4 bytes)
- unsigned int (4 bytes)
- `long` (4 bytes), synonym for int
- `unsigned long` (4 bytes), synonym for unsigned int
- long long (8 bytes)
- unsigned long long (8 bytes)
- float (4 bytes)
- double (8 bytes)
- strings
- arrays
- enum
- numeric types

Conversion

- char()
- byte()
- int()
- long()
- float()
- double()

Variable Scope & Qualifiers

- variables, scope
- static
- volatile
- const

Utilities

- sizeof()

Digital I/O

- pinMode()
- digitalWrite()
- digitalRead()
- togglePin()
- toggleLED()
- isButtonPressed()
- waitForButtonPress()

Analog I/O

- analogRead()
- pwmWrite() (analogWrite() is also available, though its use is discouraged)

Advanced I/O

- tone(): TODO
- noTone(): TODO
- shiftOut()
- pulseIn(): TODO

Time

- millis()
- micros()
- delay()
- delayMicroseconds()

Math

- min()
- max()
- abs()
- constrain()
- map()
- pow()
- sqrt()

Trigonometry

- sin()
- cos()
- tan()

Random Numbers

- randomSeed()
- random()

Bits and Bytes

- lowByte()
- highByte() is provided, though its use is discouraged.
- bitRead()
- bitWrite()
- bitSet()
- bitClear()
- bit()

External Interrupts

- Reference Page
- attachInterrupt()
- detachInterrupt()

Interrupts

- interrupts()
- noInterrupts()

Communication

- SerialUSB
- Serial

## `ASSERT(...)`

The `ASSERT()` function can be very useful for basic program debugging. It accepts a boolean; for example:

    ASSERT(state == WAIT);

Zero is false and any other number is true. If the boolean is true, the assertion passes and the program continues as usual. If it is false, the assertion fails: the program is halted, debug information is printed to USART2, and the status LED begins to throb in intensity (it’s noticeably different from blinking). The debug information is printed at 9600 baud and consists of the filename and line number where the particular assertion failed.

Including assertions in a program increases the program size. When using libmaple from the command line only, they can be disabled by making the definition

    #define DEBUG_LEVEL DEBUG_NONE

before including either wirish.h or libmaple.h. In this case, all assertions will pass without any lost clock cycles. Note that this will not work in the IDE; even with this definition, assertions will still be enabled.

## Missing Arduino Features

analogReference()

> It is not possible to implement this function on the Maple hardware. It will be possible on the upcoming Maple Native.

word

> Readers familiar with the Arduino environment may notice that the `word` datatype is missing from the above table’s list of data types. We chose not to provide the `word` data type on the Maple. If you want a 16-bit unsigned integer, use the `uint16` type instead.

> While the Maple has 32-bit words, the word size on an Arduino board is only 16 bits, and code that uses the `word` type is likely to rely on that fact.

> By not supporting `word`, you’ll get a compile error when porting Arduino code to the Maple instead of potentially weird, hard-to-debug runtime behavior.

> If you really must have `word`, you can include the following `typedef` in your program:

>     typedef uint16 word;

## Unimplemented Arduino Features

The following Wiring/Arduino features are currently unimplemented on the Maple.

- tone()
- noTone()
- pulseIn()
- String

## C++ for Maple

If you haven’t programmed in C++, or if you just need to jog your memory, you may want to check out our Language Index. It provides some introductory coverage of programming ideas and C++.

## Note for C/C++ Hackers

This is a note for programmers comfortable with C or C++ who want a better understanding of the differences between C++ and the Wiring language.

The good news is that the differences are relatively few; Wiring is just a thin wrapper around C++. Some potentially better news is that the Maple can be programmed using a standard Unix toolchain, so if you’d rather stick with gcc, make, and friends, you can. If you’re using the Unix toolchain and want to skip past the Wiring conveniences and get straight to registers, you are encouraged to move on to the libmaple documentation.

A sketch is the IDE’s notion of a project; it consists of one or more files written in the Wiring language, which is mostly the same as C++. The major difference between the two is that in Wiring, it’s not necessary to declare global functions before they are used. That is, the following is valid Wiring, and `f()` returns `5`:

    int f() {
      return g();
    }

    int g() {
      return 5;
    }

All of the files in a sketch share the same (global) namespace. That is, the behavior is as if all of a sketch’s files were part of the same translation unit, so they don’t have to include one another in order to access each other’s definitions. The only other major difference between Wiring and C++ is that Wiring doesn’t support dynamically allocated memory – that is, `new` and `delete` won’t work. As of June 01, 2011, Maple only has 20 KB RAM, anyway, so it’s doubtful that static allocation is not what you want.

The Wiring language also does not require you to define your own `main` method (in fact, we currently forbid you from doing so). Instead, you are required to define two functions, `setup` and `loop`, with type signatures

    void setup(void);
    void loop(void);

Once a sketch is uploaded to a Maple and begins to run, `setup()` is called once, and then `loop()` is called repeatedly. The IDE compilation process proceeds via a source-to-source translation from the files in a sketch to C++.

This translation process first concatenates the sketch files, then parses the result to produce a list of all functions defined in the global scope. (We borrow this stage from the Arduino IDE, which in turn borrows it from Wiring. It uses regular expressions to parse C++, which is, of course, Bad and Wrong. In the future, we’ll do this correctly, using a better parser. Until then, you have our apologies.) The order in which the individual sketch files are concatenated is not defined; it is unwise to write code that depends on a particular ordering.

The concatenated sketch files are then appended onto a file which includes WProgram.h (which includes the wirish and libmaple libraries, and declares `setup()` and `loop()`), and then provides declarations for all the function definitions found in the previous step. At this point, we have a file that is a valid C++ translation unit, but lacks `main()`. The final step of compilation provides `main()`, which behaves roughly like:

    int main(void) {
      // Call libmaple's built-in initialization routines
      init();

      // Perform the user's initialization
      setup();

      // Call user loop() forever.
      while (true) {
          loop();
      }
    }

(The truth is a little bit more complicated, but not by much).

As an example, consider a sketch with two files. The first file contains `setup()` and `loop()`:

    int the_pin;

    void setup() {
      the_pin = choose_a_pin();
      pinMode(the_pin, OUTPUT);
    }

    void loop() {
      togglePin(the_pin);
    }

The second file contains the (not very useful) implementation for `choose_a_pin()`:

    int choose_a_pin() {
       return random(5, 15);
    }

Then the results of the concatenation process might be

    int the_pin;

    void setup() {
      the_pin = choose_a_pin();
      pinMode(the_pin, OUTPUT);
    }

    void loop() {
      togglePin(the_pin);
    }

    int choose_a_pin(void);

    int choose_a_pin() {
       return random(5, 15);
    }

Which could plausibly be turned into the final source file

    #include "WProgram.h"

    void setup(void);
    void loop(void);
    int choose_a_pin(void);

    int the_pin;

    void setup() {
      the_pin = choose_a_pin();
      pinMode(the_pin, OUTPUT);
    }

    void loop() {
      togglePin(the_pin);
    }

    int choose_a_pin(void);

    int choose_a_pin() {
       return random(5, 15);
    }

    int main() {
      init();
      setup();
      while (true) loop();
    }

## Recommended Reading

- libmaple Documentation

- Your board’s Board Hardware Documentation page

- ST Documentation:
    - Reference Manual RM0008 (PDF). This is the most important reference work on the STM32 line, and covers the low-level hardware capabilities and interfaces in great detail.
    - Programming Manual (PDF). This is an assembly language and register reference for the STM32 line.
- ARM Documentation:
    - Cortex-M3 Technical Reference Manual, Revision r1p1 (PDF). This ARM manual specifies much of the the Cortex M3 Architecture, including instruction timings.

- newlib Documentation

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