在Arduino上用Java编程
序
继两个星期前成功实现了java版JVM bytecode解释器TotoroVM（见：http://edisonlovecola.iteye.com/blog/1860545)之后，边着手在arduino平台上实现它c++版，边更新博客（由于忙着实现功能，拖延了更新，以后补上这部分内容）。写完了解释器的代码解释部分，就遇到了从class文件从哪里读取的问题。
Arduino Uno存储分为2K的RAM，1K的EEPROM和32K的Flash，根据java版解释器的经验，一套基本的java框架，至少包含Object, Class, String类，再加上系统功能调用的System和Arduino类，怎么说都不可能压缩到2K内存以下。也考虑过用SD卡来当外存在保存，细想一下，又会有读取速度和通用性的瓶颈，就在我设法压缩ConstantPool大小的过程中。一个新的想法诞生－何不干脆就放弃保存ConstantPool，将它的信息固化到代码中，再进一步，就是直接把java的bytecode直接编译成c++代码，再用avr-gcc进行二次编译，这样还可以充分利用avr-gcc的优化功能。
考虑之后，觉得这个方法可行，经过两个星期的努力，今天TotoroVM Compile版正式诞生。
先试编译一个简单的Arduino程序，类似Blink程序，让13号led灯一秒闪一次：
Main程序代码
package console;
import arduino.Arduino;
import arduino.Serial;
public class Main extends Arduino {
public Main() {
pinMode(13, OUTPUT);
}
private boolean v = false;
public void loop() {
digitalWrite(13, v = !v);
delay(1000);
}
public static void main(String[] args) {
new Main().start();
}
}
Arduino基本类:
package arduino;
public abstract class Arduino {
public static final int HIGH = 1;
public static final int LOW = 0;
public static final int INPUT = 0;
public static final int OUTPUT = 1;
public static final int INPUT_PULLUP = 2;
public static final int SS = 10;
public static final int MOSI = 11;
public static final int MISO = 12;
public static final int SCK = 13;
public static final int SDA = 18;
public static final int SCL = 19;
public static final int LED_BUILTIN = 13;
public static final int A0 = 14;
public static final int A1 = 15;
public static final int A2 = 16;
public static final int A3 = 17;
public static final int A4 = 18;
public static final int A5 = 19;
public static final int A6 = 20;
public static final int A7 = 21;
public static native void init();
public static native void pinMode(int pin, int mode);
public static native void digitalWrite(int pin, boolean val);
public static native boolean digitalRead(int pin);
public static native void analogReference(int mode);
public static native int analogRead(int pin);
public static native void analogWrite(int pin, int val);
public static native long millis();
public static native long micros();
public static native void delay(long ms);
public static native void delayMicroseconds(int ms);
public static native long pulseIn(int pin, int state, long timeout);
public static native void shiftOut(int dataPin, int clockPin, int bitOrder, byte val);
public static native byte shiftIn(int dataPin, int clockPin, int bitOrder);
public Arduino() {
init();
}
public void loop() {}
public void start() {
for(;;) loop();
}
}
编译结果：
#include "console_Main.h" // console/Main.() jboolean console_Main__implements_(jreference clz) { return arduino_Arduino__implements_(clz); } // console/Main. () jboolean console_Main__extends_(jreference clz) { if (clz == 72) return 1; return arduino_Arduino__extends_(clz); } // console/Main. () vfunc console_Main__functions_(jint index) { if (index == 1) return console_Main_loop__V; return arduino_Arduino__functions_(index); } // console/Main. () vfunc console_Main__interface_functions_(jreference intf, jint index) { return arduino_Arduino__interface_functions_(intf, index); } // console/Main. ()V void console_Main__init___V() { jint vi = si - 1; si = vi + 1; _0: // ALOAD_0 apush(avalv(0)); _1: // INVOKESPECIAL arduino_Arduino__init___V(); _4: // ALOAD_0 apush(avalv(0)); _5: // ICONST_0 ipush(0); _6: // PUTFIELD tmp1.z = zpop(); tmp2.a = apop(); field_z_console_Main_v(tmp2.a) = tmp1.z; _9: // BIPUSH ipush(13); _11: // ICONST_1 ipush(1); _12: // INVOKESTATIC arduino_Arduino_pinMode_II_V(); _15: // RETURN si = vi; return; } // console/Main.loop()V void console_Main_loop__V() { jint vi = si - 1; si = vi + 1; _0: // BIPUSH ipush(13); _2: // ALOAD_0 apush(avalv(0)); _3: // ALOAD_0 apush(avalv(0)); _4: // GETFIELD tmp1.a = apop(); zpush(field_z_console_Main_v(tmp1.a)); _7: // IFEQ if (! (ipop() == 0) ) { _10: // ICONST_0 ipush(0); _11: // GOTO goto _15; } _14: // ICONST_1 ipush(1); _15: // DUP_X1 dups(0, 1); dups(1, 2); dups(2, 0); si++; _16: // PUTFIELD tmp1.z = zpop(); tmp2.a = apop(); field_z_console_Main_v(tmp2.a) = tmp1.z; _19: // INVOKESTATIC arduino_Arduino_digitalWrite_IZ_V(); _22: // LDC2_W lpush(1000); _25: // INVOKESTATIC arduino_Arduino_delay_J_V(); _28: // RETURN si = vi; return; } // console/Main.main([Ljava/lang/String;)V void console_Main_main__Ljava_lang_String__V() { jint vi = si - 1; si = vi + 1; _0: // NEW apush(allocateInstance(72, 1)); _3: // DUP dups(0, 1); si++; _4: // INVOKESPECIAL console_Main__init___V(); _7: // INVOKEVIRTUAL getVirtualFunction(avals(1), 2)(); _10: // RETURN si = vi; return; }
在电脑上Windows系统中以MinGW编译通过，回家后实战测试Arduino平台!
放上编译结果的C++项目，MinGW和cygwin的gcc应该都可以用。
打算再过一段时候和java版翻译器一起开源，sourceforge还是github呢？求推荐！