[ECOS] Tcl under eCos

[Sergei Gavrikov]

It is a tale how I got a Tcl under eCos. May be it will be interesting 
for somebody.

Sergei Gavrikov
-------------- next part --------------
How to get Tcl under eCos

Content

     Foreword
  i. Build the eCos tree
 ii. Build tclsh for eCos
iii. Test your Tcl under eCos
 iv. Extend it
 vi. Is that tclsh much sucks? No, it isn't!


Foreword

A Tcl porting for eCos is a honorable task. We hear about Java, Python ... on
the embedded systems, but why not Tcl?

Why do it?  I think it's cool, let make Tcl to toggle a led on your board:

% while {1} {foreach {state} {0 1} {led $state; after 1000}}

If speak seriously, Tcl is a good tool for any test purposes. For example, a
tclsh is built in Cisco CLI (it's known as IOS). Tcl can be a universal glue
for eCos applications too. The eCos is a RTOS. But it is an application only in
same time.  It hasn't *nix fork, exec. And what's about Tcl 'source' command
instead exec sys-call or a recompile/load practice? I think can introduce some
stuffs like a 'suspend/resume "that thread"' in Tcl, for example. It is a idea,
isn't? 

Well, but lets to do the Tcl for eCos firstly. No configtool, bash only.

i. Build the eCos tree

$ export TARGET=yours
$ mkdir -p /tmp/tclsh+ecos ; cd /tmp/tclsh+ecos
$ ecosconfig new $TARGET default
$ ecosconfig add posix
$ ecosconfig fileio romfs ramfs # it's optional
$ ecosconfig resolve

Note: to reduce a lib size fix a compiler CFLAGS (replace '-g -O2' on '-Os' in
the ecos.ecc)

I use RAM startup to test 'tclsh' under RedBoot. I have one serial on my target
board, so I need in a bit fix ecos.ecc (you can pass a import below)

$ cat >import.ecm<<__eof
cdl_component CYGDBG_HAL_DIAG_TO_DEBUG_CHAN {user_value 0};
cdl_option CYGSEM_HAL_DIAG_MANGLER {user_value None};
cdl_option CYGSEM_HAL_VIRTUAL_VECTOR_INHERIT_CONSOLE {user_value 1};
__eof
$ ecosconfig import import.ecm
$ ecosconfig resolve

now make the eCos libraries

$ ecosconfig tree
$ make


ii. Build tclsh for eCos

We will be use one of the Tcl flavors for embedded. There is a Jim interpreter
in Internet (http://jim.berlios.de). It is ultra small thing, lib size is
~70-80 kb only!  There is no Tcl sockets, I/O channels in the Jim. But it is
Tcl! It isn't 7.X, but 8.5! Jim is faster than Tcl 7.6 but slower than Tcl 8.4.
And more, the Jim licensed under the Apache License, Version 2.0. (it likes an
eCos license).

Why is no real Tcl port here? Just I have small memory foot print system (1M
RAM only). What's more? Jim is just 2 files only: jim.h, jim.c! If you have the
more power board, you can try to build a native Tcl for eCos. Welcome! It is
the honorable efforts!

So, lets download the jim-hourly.tar.gz file from that site. And build your Tcl
for eCos.

$ tar xzvf /tmp/jim-hourly.tar.gz
$ cd jim
$ export PREFIX=arm-elf- # it is my case
$ ${PREFIX}gcc -I../install/include -DJIM_ANSIC -nostartfiles -nostdlib \
-L../install/lib -Ttarget.ld -Os -o tclsh jim.c jimsh.c

What's about a library size? In my case with the arm-elf-gcc 3.2 compiler I
got:

$ arm-elf-size jim.o
   text    data     bss     dec     hex filename
  97344    1604       0   98948   18284 jim.o

For the native (Linux build) it's ~80k only!

$ cc -DJIM_ANSIC -Os -o jim jim.c jimsh.c
$ size jim
   text    data     bss     dec     hex filename
  82644    2080     448   85172   14cb4 jim


iii. Test your Tcl under eCos

Load and create a FIS entry for tclsh:

RedBoot> lo -m xmodem
RedBoot> fis create tclsh
RedBoot> fis load tclsh
RedBoot> go

...

Play with Tcl now!


iv. Extend it

You can add the eCos mount commands before run a interpreter in the jimsh.c:
main.  I add a mounting of the romfs/ramfs file systems usually. A bit hacking
let you to add any extensions.  There is jim-aio.c in the jim package. You get
a light file i/o functions with it. I just merged this with jim.c (the Tcl's
'load', 'package' commands aren't useful in our case, can cut it). I needed in
the Tcl 'glob' and 'file' commands and a funny 'led' command absolutely!  Last
days I added these stuffs for myself (and I like native tclsh prompt too :).


v. Sample of my Tcl session under eCos

+
RedBoot(tm) bootstrap and debug environment [ROM]
Non-certified release, version 1.1 - built 21:22:10, Jun  6 2006
...
RAM: 0x81000000-0x81100000, [0x81006f00-0x810ed000] available
FLASH: 0x80000000 - 0x80400000, 64 blocks of 0x00010000 bytes each.
== Executing boot script in 10.000 seconds - enter ^C to abort
RedBoot> fis load tclsh
RedBoot> go
% # Let's try some things ...
% glob /lib/*
/lib/hello.tcl /lib/init.tcl /lib/panic.tcl
% source /lib/hello.tcl
hello, world!
% cat /lib/hello.tcl
puts "hello, world!"
% lsort [info commands]
* + - / aopen append break cat catch clear collect concat continue debug dict
env error eval exit expr finalize for foreach format getref glob global if incr
info join lambda lambdaFinalizer lappend led lindex linsert list llength lmap
lrange lreverse lset lsort proc puts rand range ref rename repeat return scan
set setref source split string subst switch tailcall testmalloc time unset
uplevel upvar while
% exit


vi. Is that tclsh much sucks? No, it isn't!

RedBoot> fis list
Name              FLASH addr  Mem addr    Length      Entry point
RedBoot           0x80000000  0x81008000  0x00020000  0x81008040
romfs             0x80020000  0x81007000  0x00010000  0x81007000
tclsh             0x80030000  0x81008000  0x00040000  0x81008040
FIS directory     0x803F0000  0x803F0000  0x0000F000  0x00000000
RedBoot config    0x803FF000  0x803FF000  0x00001000  0x00000000

I wrote a Tcl 'testmalloc' command to do a out of memory panic. How I spoken,
my board has 1M RAM only.  There are RedBoot stuffs (~32k), tclsh (~220k) and
startup scripts in the RAM, and output of a test script was

% source /lib/panic.tcl
free(malloc(1024)) [1 kb passed]
free(malloc(2048)) [2 kb passed]
free(malloc(3072)) [3 kb passed]
free(malloc(4096)) [4 kb passed]
...
free(malloc(765952)) [748 kb passed]
free(malloc(766976)) [749 kb passed]
free(malloc(768000)) [750 kb passed]
free(malloc(769024)) [751 kb passed]

TCL INTERPRETER PANIC: Out of memory

---

Thanks for your time, any suggestion welcome!

Regards,

	Sergei Gavrikov
-------------- next part --------------
-- 
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss