Difference between revisions of "Forth"
m (→Adding new words) |
m (→Adding new words) |
||
Line 20: | Line 20: | ||
#define FILEIO /* File I/O primitives */ | #define FILEIO /* File I/O primitives */ | ||
#define GERTBOARD /* Gertboard functions */ | #define GERTBOARD /* Gertboard functions */ | ||
+ | </pre></code> | ||
+ | |||
+ | Include the gb_common.h right after include <math.h> | ||
+ | <code><pre> | ||
+ | #ifdef MATH | ||
+ | #include <math.h> | ||
+ | #endif | ||
+ | |||
+ | #ifdef GERTBOARD | ||
+ | #include "gb_common.h" | ||
+ | #endif | ||
</pre></code> | </pre></code> | ||
Revision as of 06:53, 7 July 2013
Forth on RPi
sudo apt-get install wget
wget http://www.fourmilab.ch/atlast/download/1.2/atlast-1.2.tar.gz
tar -xzvf atlast-1.2.tar.gz
cd atlast-1.2/
make
Start the Forth interpreter with ./atlast and exit with Ctrl-D
atlast.html and atlast.pdf is included and an is an extensive atlast-forth manual. Read it online [1] and read about Forth itself here [2] (Beware that the Forth dialect in the book Starting Forth is a bit outdated compared to Atlast Forth).
Adding new words
Most of the power of Atlast derives from the ease with which C coded primitives can be added to the language. In my case I will add some words for controlling my Gertboard. There is a detailed description on how to do this in the atlast-forth manual. And you can copy much of the word implementations from the gertboard_sw directory if you have downloaded the gertboard demo files. It is easy to add your own words, just add a "define GERTBOARD" to atlast.c around line 56.
#define EVALUATE /* The EVALUATE primitive */
#define FILEIO /* File I/O primitives */
#define GERTBOARD /* Gertboard functions */
Include the gb_common.h right after include <math.h>
#ifdef MATH
#include <math.h>
#endif
#ifdef GERTBOARD
#include "gb_common.h"
#endif
Then add your own word definitions at the end of the section with word definitions, around line 2704, right after #endif /* COMPILERW */ in atlast.c
#ifdef GERTBOARD
prim P_gert_setport() // channel state ---
{ // Set a digital io port to a specified state
int rev;
Sl(2);
// Map the I/O sections
setup_io();
if (S1 > 25)
trouble("Max GPIO is 25");
if (S1 == 21)
{ // first find out which rev of RPi we have
rev = pi_revision();
if (rev != 1)
// GP21 on Gertboard is controlled by GPIO27
S1 = 27;
}
INP_GPIO(S1);
OUT_GPIO(S1);
if (S0 == 1)
GPIO_SET0 = (1<<S1);
else
GPIO_CLR0 = (1<<S1);
Pop2;
}
prim P_gert_getport() // channel ---
{ // Get the state of a digital port
Sl(1); // Make sure there is at least one param on the stack
// Your code goes here
}
#endif /* GERTBOARD */
And finally, add the actual words to the Table of primitive words, right after #endif /* EVALUATE */ at line 2960 or so.
#ifdef EVALUATE
{"0EVALUATE", P_evaluate},
#endif /* EVALUATE */
#ifdef GERTBOARD
{"0SETIO", P_gert_setport},
{"0GETIO", P_gert_getport},
#endif /* GERTBOARD */
As we are using code from the Gertboard demos, copy the files gb_common.o and gb_common.h from the gertboard_sw directory to atlast-1.2 directory (it's there if you have run make in this directory as well).
Add gb_common.o to the file Makefile in atlast-1.2.
ATLOBJ = atlast.o gb_common.o atlmain.o
Now, save and run "make" again to recompile atlast.c.
Test the new word
Wire up the Gertboard according to the information you get when you run the command sudo ./leds in the Gertboard demo directory.
Run sudo ./atlast in the atlast-1.2 directory.
Type 22 1 setio and press enter, the corresponding LED will go on.
Type 22 0 setio and the LED will go off.
Play with it
Define your own LED demo, start the interpreter with sudo ./atlast. Define three words:
: leds 25 24 23 22 21 18 17 11 10 9 8 7 ;
: ledon 12 0 do 1 setio loop ;
: ledoff 12 0 do 0 setio loop ;
Now type: leds ledon and all leds should go on. Type leds ledoff and they should go off again.