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https://web.archive.org/web/20070514174735id_/http://wiki.rubygarden.org/Ruby/page/show/RubyOnUCLinux

Richard Keene - Colt Technologies

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Keywords: cross compile ARM Ruby SBC SBC1625 SBC-1625 Micro/Sys configure gcc kermit uCLinux

Ruby cross compile to ARM processor from PC Linux i386 machine

Target is a sbc-1625 from Micro/Sys with an extra 4 port serial board.

• PC-104 form factor.
• 16MB ram, 32MB rom, no insertable flash memory/disk

• uCLinux pre-loaded in flash.

• The host linux PC is 192.168.1.53

• The ARM PC104 board is 192.168.1.200

Serial Monitor ∞

There is a mistake in the docs for the SBC1625.
The serial port is COM1, not COM2

I use kermit to talk to it and here is the .mykermrc which gets run when you run kermit...

set line /dev/ttyS0
set speed 115200
set flow none
set carrier-watch off
connect

You will need to be superuser and

chmod 777 /dev/ttyS0

for the above scripts to work as a normal user.

general uCLinux ∞

The SBC1625 boots up with an IP address of 192.2..... which is not what my subnet is. In my copy of the file system I changed the rc file to have the correct address.

Until that was correct, I do

ifconfig ixp0 192.168.1.200

to set the IP address after boot.

Test of Compiler and ARM ∞

First get a simple helloworld.c to compile on the i386 host and run on the ARM processor. This is a good sanity check to see if you installed the SBC1625 CDROM correctly on your linux box. If this does not work then when configure runs (below) it will complain "Compiler cannot create executables". My CD is SW4122 Rev. D

The helloworld.c is like

#include <stdio,h>
int main() {
        printf("Hello world\n");
}

Then cross compile it...

/usr/local/bin/arm-linux/gcc -mbig-endian main.c

and you get an a.out file. If not then you probably need -I /usr/local/arm-linux/include on the gcc line too:

/usr/local/bin/arm-linux/gcc -mbig-endian -I /usr/local/arm-linux/include main.c

I then rename a.out to hello and copy it to /tftpboot

Then boot the ARM processor.

Then

tftp -r hello -l hello -g 192.168.1.53

(See below if tftp is not working.)

Then run it...

./hello

It should print Hello world. to the console.

Now we need to build Ruby.

Get Ruby from www.ruby-lang.org

I unpacked it into a directory called ruby-arm.

The autoconf configures for your system. It reads the Makefile.in and other files and generates the configure file.

In ext you need to edit the Setup file to enable features you need.

I uncommented the option nodynamic and socket then run...

autoconf

Now we run configure to generate the Makefiles.

configure -host i386-pc-linux -target arm-linux

Then edit the Makefile to fix the -mbig-endian problem in the CC= statement.

I think this is because the ARM processor can be wired to run in big or little-endian modes. The SBC1625 is big-endian.

It also seems to get the gcc path wrong. I think it expects your path to be correct for the cross compiler, and expects it to be called gcc.

Instead it is called arm-linux-gcc.

Any way change the Makefile to read...

CC=/usr/local/bin/arm-linux-gcc

and also

CFLAGS = -mbig-endian -g -O2  -DRUBY_EXPORT

Now...

make clean
make
# ... takes a while ...
make ruby

Now you have an executable called ruby that should run on the ARM.

Sub build of special packages. ∞

Some packages in ruby are not ...rb files in lib. Instead they are ...o or ...so or ...a files that are direct C compiled code.

A good example of this is socket. When you say require 'socket' it actually links in socket.o.

You must have miniruby compiled to build these, but the miniruby compiled is for the target ARM processor. What I did after the make ran and failed on miniruby is copied the Linux PC ruby from /usr/bin/ruby to min-ruby. Then I changed the Makefile so MINIRUBY=min-ruby and re-ran make. This caused the ext directory to get looked at and Setup to get read and the modules to get read. EXCEPT, the ext's were compiled for i386 not ARM. Oops.

After compiling the ext's Makefile then tries to build the final static Ruby executable. Since it is static, Ruby never need to load a xxxx.o file.

Also the Makefile in ext/socket is messed up.

I put in...

COMPREFIX = /usr/local/bin/arm-linux-

and then put that on the CC and AR lines like...

CC = ${COMPREFIX}gcc

and

AR = ${COMPREFIX}ar

Also I had to put the -mbig-endian in two places.

CFLAGS   =  -mbig-endian -DINET6 -g -O2 -DENABLE_IPV6

and

LDSHARED = $(CC) -mbig-endian -shared

and then run make in the socket directory.

Then re-run make in the top level ruby directory, and I got an executable Ruby.

The file systems ∞

Now we need to create some files systems to upload to RAM, and later to ROM.

My root directory is a copy of the original root on the SBC and then modified some. I also have a readonly file system in ROM mounted at /colt-readonly.

Lets get a copy of the actual file system on the SBC... On the sbc when the boot up shows a '+' hit control-c twice and wait for it to drop into RedBoot's prompt.

Then

fis list

And you see...

Name              FLASH addr  Mem addr    Length      Entry point
RedBoot           0x50000000  0x50000000  0x00040000  0x00000000
zImage            0x50040000  0x01600000  0x000C0000  0x01600000
ramdisk           0x50100000  0x00800000  0x00360000  0x00800000
FIS directory     0x50FE0000  0x50FE0000  0x0001F000  0x00000000
RedBoot config    0x50FFF000  0x50FFF000  0x00001000  0x00000000

These are pre-loaded chunks of info that can be copied to ram and run.

It turns out that the ramdisk image is called /dev/rom0 when Linux is booted.

Anyway, cycle the power and reboot the board to Linux.

/dev/rom2 is the filesystem.

so...

ifconfig ixp0 192.168.1.200
tftp -l /dev/rom2 -r fs.gz -p 192.168.1.53

Then on the host as super user...

cd /tftpboot
gunzip myrom2

(ignore the error message abut the file being truncated.)

Now you have a file fs that is the file system image.

You can mount it...

mkdir /mnt/fs
mount -o loop fs /mnt/fs

And then...

ls /mnt/fs

And you see...

bin  dev  etc  home  lib  lost+found  mnt  proc  sbin  tmp  usr  var

This is the root file system.

MAKE A SAFE BACKUP OF THIS FILE

You can now modify the file system and then load it back onto the SBC and see it there.

cd /mnt/fs
vi junk.txt
# [Edit in a nifty message and save back out with vi]
cd /tftpboot
umount /mnt/fs

Then back on the SBC cycle the power and at the '+' type control-c twice

Then at the RedBoot prompt type the following (The -- comments on the end are not typed)

ip_address -l 192.168.1.200 -h 192.168.1.53   -- This sets the IP up
fis load zImage                               -- Copies linux from rom to ram
load -r -b 0x00800000 fs                      -- Copies the files system with tftp from the host
go -n 0x01600000                              -- Runs linux.

You should see linux boot.

Then

cd /
ls

And you should see the junk.txt

more junk.txt

You should see your nifty message.

Usefull sequences of commands ∞

The ...txt commands I usually list to the screen and cut-and-past to the kermit window.

The ....sh commands are run directly as root to mount and unmount files systems.

As the SBC is booting it emits a '+'

If you press control-c twice or more it will stop RedBoot and give you a RedBoot> prompt.

Here you can do nifty things like

fis list

This lists the flash memory segments and what they are called.

Here are some scripts I use. The 'fs' is the read-write root file system image on the host. 'rofs' is the readonly file system with ruby in it. It stays in /dev/rom3 and gets mounted from there.

This is the sequence of commands to set the IP addresses up, move Linux from ROM to RAM, then tftp down
the file system image, then run Linux.

Note that we also setup the IP address of the board and host. That is how load knows where to go.

uploadfs.txt ∞

ip_address -l 192.168.1.200 -h 192.168.1.53
fis load zImage
load -r -b 0x00800000 fs
go -n 0x01600000

This next one uploads both zLinux and the 'fs' root file system.

uploadboth.txt ∞

ip_address -l 192.168.1.200 -h 192.168.1.53
load -r -b 0x01600000 zImage
load -r -b 0x00800000 fs
go -n 0x01600000

This downloads the readonly files system with ruby and our app to rom3. You do this after Linux is booted on the SBC-1625. This takes a while to run since the device is writing to flash ROM. (more than a minute)

rom3upload.txt ∞

umount /colt-readonly
tftp -r rofs -l /dev/rom3 -g 192.168.1.53
mount -o loop /dev/rom3 /colt-readonly

I strongly recommend that you copy /dev/rom0,1,2,3 to your host for safe keeping. You can do this by booting the board and using tftp to copy the files.

Like...

tftp -l /dev/rom0 -r rom0 -p 192,168.1.53

I think rom0 is RedBoot, rom1 is zLinux.

I know rom2 is the file system. rom3 is empty and we will later put a read-only file system with Ruby and our application in it.

Here are some shell scripts to automate host side stuff.

Note: If the file systems are mounted in /mnt on the host and you make a change, you can just type sync on the host and then load the file system. You do not have to always be typing mnt.sh and umnt.sh

mnt.sh ∞

#!/bin/bash
umount /mnt/fs
umount /mnt/rofs
mount -o loop /tftpboot/fs /mnt/fs
mount -o loop /tftpboot/rofs /mnt/rofs
echo /tftpboot/fs is now mounted on /mnt/fs
echo /tftpboot/rofs is now mounted on /mnt/rofs

umnt.sh ∞

#!/bin/bash
umount /mnt/fs
umount /mnt/rofs

Setting up tftp on Fedora Linux host ∞

You need to have tftpd running. You must edit the /etc/xinted.d/tftp file so it allows creation of files by clients.

# default: off
# description: The tftp server serves files using the trivial file transfer \
#       protocol.  The tftp protocol is often used to boot diskless \
#       workstations, download configuration files to network-aware printers, \
#       and to start the installation process for some operating systems.
service tftp
{
        disable = no
        socket_type             = dgram
        protocol                = udp
        wait                    = yes
        user                    = root
        server                  = /usr/sbin/in.tftpd
        server_args             = -c -s /tftpboot
        per_source              = 11
        cps                     = 100 2
        flags                   = IPv4
}

The -c there allows creation of files.

If the sbc says tftp: timeout it means that the tftpd is not running. You now can put files in /tftpboot and the RedBoot can copy them. Also you can use tftp on the SBC in Linux to get and put files.

Serial Ports ∞

On Linux, serial ports are called /dev/ttyS0 and such. You set them with the stty command, like

stty -F /dev/ttyS1 1200 raw

which sets to 1200 baud and raw data, no parity, no hardware or XON/XOFF control. You usually need to be super user and set the serial port bits like

chmod 666 /dev/ttyS1

Final burn in ∞

When your application works perfectly you are ready to commit to ROM. We need to burn /dev/rom0 with our new root file system, and above we have shown how to burn /dev/rom3 with our readonly stuff.

Ruby Notes ∞

Ruby chokes if /usr is world writable. I had it at 777 and it should be 755. Same for /usr/bin, /etc, /sbin, /usr, /usr/sbin

The resulting cross compiled ruby fails at floating point number.

The code

sprintf("%6.2f", 101.5)

or

puts 101.5.to_s

FIXME - prints some huge weird number. Any ideas as to how to fix this out there in Ruby-land? Maybe a big-endian issue with Ruby?

Ok, stupid programmer trick #1: My application opens and sets baud rates on serial ports. I had the command to set /dev/ttyS0 to 1200 baud.

This caused all output to kermit to stop. Well duh! This is a good example of why you must have EVERYTHING working correctly before modifying /dev/rom0 which is the root file system. The ttyS0 error caused the system to unusable if in rom0. Luckily I tested it first.

Last updated 2020-11-18 at 03:26:47