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by robomon
Sun Oct 25, 2015 6:57 am
Forum: Bare metal, Assembly language
Topic: Pi 2 extra cores operation
Replies: 5
Views: 1874

Re: Pi 2 extra cores operation

Initially I was in the impression that all the cores are running in parallel from the address 0x8000. But after reading a post from the moderator(link below), I came to know that its not the case. https://www.raspberrypi.org/forums/viewtopic.php?p=789655#p789655 So if all your cores started up, be s...
by robomon
Sun Oct 25, 2015 6:39 am
Forum: Bare metal, Assembly language
Topic: Why doesn't arm-none-eabi-gcc use my custom _start symbol
Replies: 7
Views: 4390

Re: Why doesn't arm-none-eabi-gcc use my custom _start symbo

I tried adding ENTRY(symbol) to my linker script. But still no success. Please see the assembly listing created using objdump. You can see that the main is at 0x8000 and not the _start. test.c int main() { volatile int i=0; i = i+1; return 0; } start.S .globl _start _start: mov sp,#0x8000 /*stack gr...
by robomon
Sat Oct 24, 2015 5:37 pm
Forum: Bare metal, Assembly language
Topic: Why doesn't arm-none-eabi-gcc use my custom _start symbol
Replies: 7
Views: 4390

Why doesn't arm-none-eabi-gcc use my custom _start symbol

I am compiling the below code with "-nostdlib". My understanding was that arm-none-eabi-gcc will not use the _start in "crt0.o" but it will use the user defined _start. For this I was expecting to create a start.S file and put the _start symbol. But if I compile the below shown code without the _sta...
by robomon
Sat Oct 24, 2015 5:28 pm
Forum: Bare metal, Assembly language
Topic: Only Core 1 is running. Not able to get Core 0,2 and 3 run
Replies: 3
Views: 1202

Re: Only Core 1 is running. Not able to get Core 0,2 and 3 r

Yes. I am using the set and clear registers. Now I got the issue fixed. The issue was that At 0x8000 the compiler was placing the main function instead of the _start function. This caused the stack pointer not initialised. Also due to optimisation, compiler rearranged the functions in main. Because ...
by robomon
Sat Oct 24, 2015 9:15 am
Forum: Bare metal, Assembly language
Topic: How did GCC compiler know my start address is 0x8000 ?
Replies: 2
Views: 1161

How did GCC compiler know my start address is 0x8000 ?

I am compiling for a bare metal code using GCC for my Raspberry Pi 2. When I see the compiled output, I saw that the code begins at address 0x8000. Below shown is my test.c file, compiler commandline option and the objdump. Question: How did the compiler understand that the code should be placed at ...
by robomon
Sat Oct 24, 2015 8:28 am
Forum: Bare metal, Assembly language
Topic: Why does my bare metal image causes the Red LED to blink ?
Replies: 1
Views: 462

Re: Why does my bare metal image causes the Red LED to blink

I searched in the internet and found that it might be an issue with the power supply. When I replaced it, the issue got solved!

Thanks.

I am not deleting this question. Keeping it for documentation purpose.
by robomon
Sat Oct 24, 2015 8:22 am
Forum: Bare metal, Assembly language
Topic: Why does my bare metal image causes the Red LED to blink ?
Replies: 1
Views: 462

Why does my bare metal image causes the Red LED to blink ?

I have a bare metal code written for Raspberry Pi 2. When I put the image into the SD card and make Raspberry Pi to execute, the code is executed properly. But the Red led(I think it is the power LED) blinks for 2 or 3 times initially. If you want to see , you can get the kernel.img from this link -...
by robomon
Wed Sep 30, 2015 9:10 pm
Forum: Bare metal, Assembly language
Topic: Only Core 1 is running. Not able to get Core 0,2 and 3 run
Replies: 3
Views: 1202

Only Core 1 is running. Not able to get Core 0,2 and 3 run

I have written a bare metal multi core example. In that I am only able to start Core 1 (by writting the start address to the mailbox). After that execution doesn't goes to Core 0,2 and 3. In my example, there are 3 LED's connected to the GPIO pins of the raspberry Pi. There are totally 4 cores in Ra...
by robomon
Thu Aug 27, 2015 8:34 pm
Forum: Bare metal, Assembly language
Topic: How to do QEMU emulation for bare metal Raspberry Pi images
Replies: 0
Views: 808

How to do QEMU emulation for bare metal Raspberry Pi images

I would like to emulate using QEMU the bare metal Raspberry Pi examples provided in this link - https://github.com/dwelch67/raspberrypi. Could someone let me know which commandline arguments should I use to get QEMU running. I checked in the internet and found that almost all the QEMU raspberry Pi t...

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