Bare metal

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(New page: Here is an example of how to run your own code on the bare metal, without any operating system.)
 
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Here is an example of how to run your own code on the bare metal, without any operating system.
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Here is an example of how to run your own C code on the bare metal, without any operating system. Since I don't yet have a physical device, this has only been tested using [[Qemu]].
 +
 
 +
== Example program ==
 +
 
 +
The example program does nothing but blink the LCD backlight on and off.  A simple first exercise might be to change it to blink out "hello world" in morse code.
 +
 
 +
=== C code (app.c) ===
 +
 
 +
<pre>
 +
#define GPBDAT *((volatile unsigned long*)0x56000014)
 +
 
 +
void cstart(void)
 +
{
 +
int i;
 +
while (1) {
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GPBDAT ^= 1; /* toggle the backlight */
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for (i = 0; i < 50000000; i++); /* delay a little bit */
 +
}
 +
}
 +
</pre>
 +
 
 +
=== Assembler head (app.S) ===
 +
 
 +
<pre>
 +
.text
 +
.globl _start
 +
_start:
 +
mov sp, #0x30000000    @ start of RAM
 +
add sp, sp, #0xa00000  @ 10mb in, should be a safe place to put our stack
 +
b cstart            @ call C code
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</pre>
 +
 
 +
=== Linker script (app.lds) ===
 +
 
 +
<pre>
 +
SECTIONS
 +
{
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  . = 0x35000000;
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}
 +
</pre>
 +
 
 +
=== Makefile ===
 +
 
 +
<pre>
 +
CROSS=/mnt/oe/openmoko/build/tmp/cross/arm-angstrom-linux-gnueabi/bin/
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CC=${CROSS}gcc
 +
OBJCOPY=${CROSS}objcopy
 +
 
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app.bin: app.elf
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${OBJCOPY} -O binary $^ $@
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app.elf: app.S app.c
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${CC} -Wall -nostdlib $^ -o $@ -T app.lds
 +
</pre>
 +
 
 +
== Using with qemu ==
 +
 
 +
Terminal 1:
 +
<pre>
 +
~/tmp % wget http://meshy.org/~ato/upload/bare-metal-moko.tar.gz
 +
  % Total    % Received % Xferd  Average Speed  Time    Time    Time  Current
 +
                                Dload  Upload  Total  Spent    Left  Speed
 +
100  3322  100  3322    0    0  4156      0 --:--:-- --:--:-- --:--:--  8384
 +
~/tmp % tar -zxf bare-metal-moko.tar.gz
 +
~/tmp % cd bare-metal-moko
 +
~/tmp/bare-metal-moko % make
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/mnt/oe/openmoko/build/tmp/cross/arm-angstrom-linux-gnueabi/bin/gcc -Wall -nostdlib app.S app.c -o app.elf -T app.lds
 +
/mnt/oe/openmoko/build/tmp/cross/arm-angstrom-linux-gnueabi/bin/objcopy -O binary app.elf app.bin
 +
</pre>
 +
 
 +
Terminal 2:
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<pre>
 +
/mnt/oe/openmoko/build/qemu % cp ~/tmp/bare-metal-moko/qemu-telnet.sh openmoko
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/mnt/oe/openmoko/build/qemu % ./openmoko/qemu-telnet.sh
 +
QEMU waiting for connection on: localhost:1200,server
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</pre>
 +
 
 +
Terminal 1:
 +
<pre>
 +
~/tmp/bare-metal-moko % kermit -y download.kerm
 +
DNS Lookup...  Trying 127.0.0.1...  Reverse DNS Lookup... (OK)
 +
localhost.localdomain connected on port 1200
 +
ÿûÿûÿûÿý
 +
       
 +
U-Boot 1.3.2-rc2 (May 22 2008 - 01:06:44)
 +
                                       
 +
I2C:  ready
 +
DRAM:  128 MB
 +
NAND:  64 MiB
 +
Found Environment offset in OOB..
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Video: 640x480x8 31kHz 59Hz     
 +
                         
 +
NAND read: device 0 offset 0x244000, size 0x5000
 +
                                               
 +
Reading data from 0x248e00 -- 100% complete.
 +
20480 bytes read: OK                     
 +
USB:  S3C2410 USB Deviced
 +
In:    serial           
 +
Out:  serial
 +
Err:  serial
 +
GTA01Bv4 # loadb 35000000
 +
## Ready for binary (kermit) download to 0x35000000 at 115200 bps...
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#                                               
 +
 
 +
# Total Size      = 0x00000064 = 100 Bytes
 +
## Start Addr      = 0x35000000         
 +
GTA01Bv4 # go 35000000       
 +
## Starting application at 0x35000000 ...
 +
</pre>
 +
 
 +
Terminal 2:
 +
<pre>
 +
...
 +
neo_bl_switch: LCD Backlight now on.
 +
neo_bl_switch: LCD Backlight now off.
 +
neo_bl_switch: LCD Backlight now on.
 +
neo_bl_switch: LCD Backlight now off.
 +
neo_bl_switch: LCD Backlight now on.
 +
neo_bl_switch: LCD Backlight now off.
 +
neo_bl_switch: LCD Backlight now on.
 +
...
 +
</pre>

Revision as of 12:27, 22 August 2008

Here is an example of how to run your own C code on the bare metal, without any operating system. Since I don't yet have a physical device, this has only been tested using Qemu.

Contents

Example program

The example program does nothing but blink the LCD backlight on and off. A simple first exercise might be to change it to blink out "hello world" in morse code.

C code (app.c) 

#define GPBDAT *((volatile unsigned long*)0x56000014)

void cstart(void)
{
	int i;
	while (1) {
		GPBDAT ^= 1; /* toggle the backlight */
		for (i = 0; i < 50000000; i++); /* delay a little bit */
	}
}

Assembler head (app.S) 

.text
.globl _start
_start:
	mov	sp, #0x30000000    @ start of RAM
	add	sp, sp, #0xa00000  @ 10mb in, should be a safe place to put our stack
	b	cstart             @ call C code

Linker script (app.lds) 

SECTIONS
{
  . = 0x35000000;
}

Makefile 

CROSS=/mnt/oe/openmoko/build/tmp/cross/arm-angstrom-linux-gnueabi/bin/
CC=${CROSS}gcc
OBJCOPY=${CROSS}objcopy

app.bin: app.elf
	${OBJCOPY} -O binary $^ $@ 

app.elf: app.S app.c
	${CC} -Wall -nostdlib $^ -o $@ -T app.lds

Using with qemu

Terminal 1: 

~/tmp % wget http://meshy.org/~ato/upload/bare-metal-moko.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  3322  100  3322    0     0   4156      0 --:--:-- --:--:-- --:--:--  8384
~/tmp % tar -zxf bare-metal-moko.tar.gz 
~/tmp % cd bare-metal-moko 
~/tmp/bare-metal-moko % make
/mnt/oe/openmoko/build/tmp/cross/arm-angstrom-linux-gnueabi/bin/gcc -Wall -nostdlib app.S app.c -o app.elf -T app.lds
/mnt/oe/openmoko/build/tmp/cross/arm-angstrom-linux-gnueabi/bin/objcopy -O binary app.elf app.bin

Terminal 2: 

/mnt/oe/openmoko/build/qemu % cp ~/tmp/bare-metal-moko/qemu-telnet.sh openmoko
/mnt/oe/openmoko/build/qemu % ./openmoko/qemu-telnet.sh 
QEMU waiting for connection on: localhost:1200,server

Terminal 1: 

~/tmp/bare-metal-moko % kermit -y download.kerm
 DNS Lookup...  Trying 127.0.0.1...  Reverse DNS Lookup... (OK)
 localhost.localdomain connected on port 1200
ÿûÿûÿûÿý
        
U-Boot 1.3.2-rc2 (May 22 2008 - 01:06:44)
                                         
I2C:   ready
DRAM:  128 MB
NAND:  64 MiB
Found Environment offset in OOB..
Video: 640x480x8 31kHz 59Hz      
                           
NAND read: device 0 offset 0x244000, size 0x5000
                                                
Reading data from 0x248e00 -- 100% complete.
 20480 bytes read: OK                       
USB:   S3C2410 USB Deviced
In:    serial             
Out:   serial
Err:   serial
GTA01Bv4 # loadb 35000000
## Ready for binary (kermit) download to 0x35000000 at 115200 bps...
#                                                

# Total Size      = 0x00000064 = 100 Bytes
## Start Addr      = 0x35000000           
GTA01Bv4 # go 35000000         
## Starting application at 0x35000000 ...

Terminal 2: 

...
neo_bl_switch: LCD Backlight now on.
neo_bl_switch: LCD Backlight now off.
neo_bl_switch: LCD Backlight now on.
neo_bl_switch: LCD Backlight now off.
neo_bl_switch: LCD Backlight now on.
neo_bl_switch: LCD Backlight now off.
neo_bl_switch: LCD Backlight now on.
...
Retrieved from "http://openmoko.org/index.php?title=Bare_metal&oldid=48415"
Personal tools

Here is an example of how to run your own code on the bare metal, without any operating system.