Booting the raspberry pi and running a bare metal program

Question

Background Info

I am attempting to write a few bare metal programs and in theory I would eventually write a kernel. To get used to the environment, I found a tutorial that was known to work to could play around with later. I have installed the necessary toolchain as required on a Raspberry Pi 3 running jessie and use that for compilation. I installed jessie lite on my SD card and removed all files except for bootcode.bin, fixup.dat, and start.elf.

To compile, I followed the instructions in the tutorial and ran make on their solution code which generated a kernel.img which I then transferred to the SD card and inserted into my Pi 2. The green light came on initially and then went out and a large rainbow square (not the low power square) appeared on the screen where it appeared to hang and not proceed. As per this guide, a colored screen means that the kernel could not be executed. Is the tutorial up to date? did I include enough files?

Code

The solution code to ok2:

/******************************************************************************
*   main.s
*    by Alex Chadwick
*
*   A sample assembly code implementation of the ok02 operating system, that 
*   simply turns the OK LED on and off repeatedly.
*   Changes since OK01 are marked with NEW.
******************************************************************************/

/*
* .section is a directive to our assembler telling it to place this code first.
* .globl is a directive to our assembler, that tells it to export this symbol
* to the elf file. Convention dictates that the symbol _start is used for the 
* entry point, so this all has the net effect of setting the entry point here.
* Ultimately, this is useless as the elf itself is not used in the final 
* result, and so the entry point really doesn't matter, but it aids clarity,
* allows simulators to run the elf, and also stops us getting a linker warning
* about having no entry point. 
*/
.section .init
.globl _start
_start:

/* 
* This command loads the physical address of the GPIO region into r0.
*/
ldr r0,=0x20200000

/*
* Our register use is as follows:
* r0=0x20200000 the address of the GPIO region.
* r1=0x00040000 a number with bits 18-20 set to 001 to put into the GPIO
*               function select to enable output to GPIO 16. 
* then
* r1=0x00010000 a number with bit 16 high, so we can communicate with GPIO 16.
* r2=0x003F0000 a number that will take a noticeable duration for the processor 
*               to decrement to 0, allowing us to create a delay.
*/
mov r1,#1
lsl r1,#18

/*
* Set the GPIO function select.
*/
str r1,[r0,#4]

/* 
* Set the 16th bit of r1.
*/
mov r1,#1
lsl r1,#16

/* NEW
* Label the next line loop$ for the infinite looping
*/
loop$: 

/*
* Set GPIO 16 to low, causing the LED to turn on.
*/
str r1,[r0,#40]

/* NEW
* Now, to create a delay, we busy the processor on a pointless quest to 
* decrement the number 0x3F0000 to 0!
*/
mov r2,#0x3F0000
wait1$:
    sub r2,#1
    cmp r2,#0
    bne wait1$

/* NEW
* Set GPIO 16 to high, causing the LED to turn off.
*/
str r1,[r0,#28]

/* NEW
* Wait once more.
*/
mov r2,#0x3F0000
wait2$:
    sub r2,#1
    cmp r2,#0
    bne wait2$

/*
* Loop over this process forevermore
*/
b loop$

Answer 1

Your question includes this

and inserted into my Pi 2

At the very top of the tutorial page, you linked to in red is the following:

This course has not yet been updated to work with the Raspberry Pi models B+ and A+. Some elements may not work, in particular the first few lessons about the LED. It has also not been updated for Raspberry Pi v2.

In particular, I draw your attention to the last sentence. So no the tutorial has not been updated and is not expected to work on a Pi 2.

Answer 2

I guess the following code works for RPi2B

/******************************************************************************
*   main.s
*    by Alex Chadwick
*           
*   A sample assembly code implementation of the ok02 operating system, that 
*   simply turns the OK LED on and off repeatedly.
*   Changes since OK01 are marked with NEW.
*
*       -- RPI2 version
******************************************************************************/

/*
* .section is a directive to our assembler telling it to place this code first.
* .globl is a directive to our assembler, that tells it to export this symbol
* to the elf file. Convention dictates that the symbol _start is used for the 
* entry point, so this all has the net effect of setting the entry point here.
* Ultimately, this is useless as the elf itself is not used in the final 
* result, and so the entry point really doesn't matter, but it aids clarity,
* allows simulators to run the elf, and also stops us getting a linker warning
* about having no entry point. 
*/
.section .init
.globl _start
_start:

/* 
* This command loads the physical address of the GPIO region into r0.
*/
ldr r0,=0x3f200000

/*
* Our register use is as follows:
* r0=0x3f200000 the address of the GPIO region.
* r1=0x00200000 a number with bits 21-23 set to 001 to put into the GPIO
*               function select to enable output to GPIO 47. 
* then
* r1=0x00010000 a number with bit 15 high, so we can communicate with GPIO 47.
* r2=0x003F0000 a number that will take a noticeable duration for the processor 
*               to decrement to 0, allowing us to create a delay.
*/
mov r1,#1
lsl r1,#21

/*
* Set the GPIO function select.
*/
str r1,[r0,#24]

/* 
* Set the 15th bit of r1.
*/
mov r1,#1
lsl r1,#15

/* NEW
* Label the next line loop$ for the infinite looping
*/
loop$: 

/*
* Set GPIO 47 to low, causing the LED to turn on.
*/
str r1,[r0,#44]

/* NEW
* Now, to create a delay, we busy the processor on a pointless quest to 
* decrement the number 0x3F0000 to 0!
*/
mov r2,#0x3F0000
wait1$:
    sub r2,#1
    cmp r2,#0
    bne wait1$

/* NEW
* Set GPIO 47 to high, causing the LED to turn off.
*/
str r1,[r0,#32]

/* NEW
* Wait once more.
*/
mov r2,#0x3F0000
wait2$:
    sub r2,#1
    cmp r2,#0
    bne wait2$

/*
* Loop over this process forevermore
*/
b loop$