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
Unique Maple Additions¶
- ASSERT(...)
The ASSERT() function can be very useful for basic program debugging. The function 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_NONEbefore 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.
Maple Language Reference¶
The following table summarizes the available core language features. A more exhaustive index is available at the Complete Language Index.
| Structure | Variables | Functions |
|---|---|---|
|
Control Structures Further syntax
Arithmetic Operators Comparison Operators
Boolean Operators Pointer Operators Bitwise Operators Compound Operators
Keywords |
Constants
Data Types
Conversion Variable Scope & Qualifiers Utilities |
Digital I/O
Analog I/O
Advanced I/O
Time Math Trigonometry Random Numbers Bits and Bytes
External Interrupts Interrupts Communication Looking for something else? See the Maple Library Reference page for interfacing with particular types of hardware. Maple links against newlib and allows the use of any of its functions; see its documentation for more details. |
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. However, they will be present in future versions:
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++ (although, you C programmers should remember that C++ is not a superset of 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.
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 March 23, 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, it forbids 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. An upcoming rewrite of the IDE performs this preprocessing step correctly, using a real 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 a main() method. The final step of compilation provides this method, which behaves roughly like:
int main(void) {
setup();
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() {
setup();
while (true) loop();
}
(Recall that it’s legal C++ for a function to be declared multiple times, as long as it’s defined exactly once).
Recommended Reading¶
STMicro documentation for STM32F103RB microcontroller:
- Datasheet (pdf)
- Reference Manual (pdf)
- Programming Manual (assembly language and register reference)
