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by dwelch67
Fri Feb 09, 2018 4:37 am
Forum: Bare metal
Topic: [SOLVED] Compilation for Cortex-M3 with ARM RPi 2B Toolchain
Replies: 2
Views: 227

Re: Compilation for Cortex-M3 with ARM RPi 2B Toolchain

While this is a baremetal forum it is a raspberry pi forum not stm32. but anyway: I have many STM32 examples along side my raspberry pi repos. You can certainly use arm-whatever-gcc if you dont need C library functions as that gets operating system dependent and what operating system are you running...
by dwelch67
Wed Feb 07, 2018 9:35 pm
Forum: Bare metal
Topic: starting to make an os for rpi
Replies: 18
Views: 1333

Re: starting to make an os for rpi

and my desire to get more folks out of and through traps tends to get me into situations like this where i am doing more bad than good writing down opinions...
by dwelch67
Wed Feb 07, 2018 9:26 pm
Forum: Bare metal
Topic: starting to make an os for rpi
Replies: 18
Views: 1333

Re: starting to make an os for rpi

I did/do like your list, well presented. need to post that on its own somewhere. your requirements/goals are ...
by dwelch67
Wed Feb 07, 2018 9:24 pm
Forum: Bare metal
Topic: starting to make an os for rpi
Replies: 18
Views: 1333

Re: starting to make an os for rpi

I fully understand what you are saying. just trying to say that there is a line you cross where you need to ask questions, working in a vacuum is a bad idea for many reasons. Where than line lands matters. If you dont try to do any of the things in your list, basically ask for everything and do litt...
by dwelch67
Sun Feb 04, 2018 3:12 am
Forum: Bare metal
Topic: starting to make an os for rpi
Replies: 18
Views: 1333

Re: starting to make an os for rpi

While you need the things on bzt's list, that doesnt mean you have to learn them on your own in a vacuum. How you learn to read technical documentation, in part is by asking someone, a mentor or the general public as that is a thing now. Do learn how to ask the question, dont come in saying I am goi...
by dwelch67
Fri Feb 02, 2018 3:35 am
Forum: Bare metal
Topic: Pi3 GPIO and UART questions
Replies: 6
Views: 523

Re: Pi3 GPIO and UART questions

I cant speak to the specific pi qemu port. But the ones I have dabbled with (used) they not only do not get into pin/pad controls and gpio muxes, they dont even fully implement the uart. You can simply write to the uart transmit register as fast as you can and the characters go out on the console, t...
by dwelch67
Fri Feb 02, 2018 3:31 am
Forum: Bare metal
Topic: starting to make an os for rpi
Replies: 18
Views: 1333

Re: starting to make an os for rpi

I see a number of folks use the term OS when later it seems they were just thinking baremetal. So I guess will see if that is the case here. Wanted to work on a baremetal program or wanted to write an operating system? Part of writing an operating system, is deciding on how and where programs are go...
by dwelch67
Thu Feb 01, 2018 10:36 am
Forum: Bare metal
Topic: starting to make an os for rpi
Replies: 18
Views: 1333

Re: starting to make an os for rpi

There are many other pre-built gnu packages. Did you try one of those, for example: https://launchpad.net/gcc-arm-embedded (which has now moved to an arm site directly) https://developer.arm.com/open-source/gnu-toolchain/gnu-rm Another: https://www.linaro.org/downloads/ I imagine the sticky tab at t...
by dwelch67
Sat Jan 27, 2018 7:16 pm
Forum: Bare metal
Topic: Using Dave Welch's bootloader07
Replies: 7
Views: 489

Re: Using Dave Welch's bootloader07

yes ihex and srec (intel hex, motorola s record, good pages on wikipedia) are ascii file formats. I use ascii in minicom to send them over.

What if you cut and paste the .hex file (from a text editor or cat or other) and paste it into the minicom terminal, no download, just paste.
by dwelch67
Sat Jan 27, 2018 7:14 pm
Forum: Bare metal
Topic: Using Dave Welch's bootloader07
Replies: 7
Views: 489

Re: Using Dave Welch's bootloader07

hmmm, interesting, I dont have a mac to try this with. what if you slow everything down, change it to 57600 on both sides or 9600, etc...
by dwelch67
Fri Jan 26, 2018 6:16 pm
Forum: Bare metal
Topic: Mini UART dropping data
Replies: 4
Views: 358

Re: Mini UART dropping data

nothing special not only am I able to keep up with xmodem I can dump a whole srecord in and keep up with that. using polling only. Perhaps the fifos are on in the uart but how big are they? it is a problem I have dealt with in the past and sadly hardware flow control often isnt, and when it is, you ...
by dwelch67
Fri Jan 26, 2018 6:13 pm
Forum: Bare metal
Topic: Mini UART dropping data
Replies: 4
Views: 358

Re: Mini UART dropping data

nothing special not only am I able to keep up with xmodem I can dump a whole srecord in and keep up with that. using polling only. Perhaps the fifos are on in the uart but how big are they? it is a problem I have dealt with in the past and sadly hardware flow control often isnt, and when it is, you ...
by dwelch67
Fri Jan 26, 2018 2:58 am
Forum: Bare metal
Topic: Understanding of RPi3 addresses
Replies: 3
Views: 335

Re: Understanding of RPi3 addresses

There are actually two processors in the broadcom BCM2835 the ARM6 and a Graphics processor specifically a videocore VC4 I assume you meant ARMv6. Just read up on it though, didnt know Apple was into arm that early, though the arm7(tdmi) was the first ARM after it was Acorn, but the ARM6 was the fi...
by dwelch67
Wed Jan 24, 2018 2:57 am
Forum: Bare metal
Topic: Baking Pi Update List
Replies: 12
Views: 818

Re: Baking Pi Update List

as far as instruction sets, no reason to limit yourself, each new instruction set you learn becomes that much easier they are more similar than different in many respects (they have an add, an xor, a load a store, etc). before aarch64 arms thumb instruction set is the most portable, or the only one ...
by dwelch67
Wed Jan 24, 2018 1:05 am
Forum: Bare metal
Topic: Baking Pi Update List
Replies: 12
Views: 818

Re: Baking Pi Update List

Just like you can still buy as well as make a profit with 8 bit processors, the 32 bit processors will not die any time soon. With respect to things like phone processors and set top box processors and tablets, those where consumers want that much more media this year than the year before, sure thos...
by dwelch67
Mon Jan 22, 2018 8:20 pm
Forum: Bare metal
Topic: Up to date way to debug Bare Metal
Replies: 6
Views: 477

Re: Up to date way to debug Bare Metal

since the assembly (gcc -S) shows pseudo code and lacks pool data, I prefer to disassemble vs compile to assembly, you get an accurate or more accurate account of what is actually going on. the gnu disassembler (arm-whatever-objdump -D myfile.elf > myfile.list) disassembles everything it can so asci...
by dwelch67
Wed Jan 17, 2018 9:35 pm
Forum: Bare metal
Topic: Difference between Interrupts in x86 and Exceptions in Arm
Replies: 5
Views: 469

Re: Difference between Interrupts in x86 and Exceptions in Arm

I hate to say it or maybe I dont, probably better off starting with a pi-zero and the ARM 11 than diving into arm with this chip. My two cents...
by dwelch67
Wed Jan 17, 2018 9:33 pm
Forum: Bare metal
Topic: JTag for Pi 3
Replies: 9
Views: 578

Re: JTag for Pi 3

serial bootloader, yes I have. well worth doing IMO. place/solder down a reset button, get some usb uart or other development machine to pi solution and just press the reset buttton and try again...

David
by dwelch67
Mon Jan 15, 2018 2:13 pm
Forum: Bare metal
Topic: JTag for Pi 3
Replies: 9
Views: 578

Re: JTag for Pi 3

I agree you dont need that, not required. but if you do get one an ftdi based part that supports mpsse is all you need, can be had for under $50, no reason to get the expensive ones. Use openocd. My jtag examples were based on the original pi, arm11 based, and a little into the armv7 based one. But ...
by dwelch67
Mon Jan 15, 2018 2:07 pm
Forum: Bare metal
Topic: Raspberry Pi 3 Kernel Development with Broadcom 2835
Replies: 2
Views: 253

Re: Raspberry Pi 3 Kernel Development with Broadcom 2835

Note the sticky topics have lots of good links, somewhere in there you will find a community based errata for the broadcom documentation, bugs in the docs that folks have found and bothered to document. No need to re-hack the same wheel.
by dwelch67
Mon Jan 15, 2018 2:06 pm
Forum: Bare metal
Topic: General Approach for a Minimal Kernel in ARM
Replies: 2
Views: 290

Re: General Approach for a Minimal Kernel in ARM

there are some sticky topics at the top of this forum that contain links to many different baremetal resources. covering framebuffer (not required for kernel development, a uart will do), mmu, usb (keyboard, etc, not required for kernel development, uart will do), booting the chip, interrupts, etc. ...
by dwelch67
Sun Jan 14, 2018 10:37 pm
Forum: Bare metal
Topic: Timer with nanosecond accuracy for electronic purpose
Replies: 15
Views: 1042

Re: Timer with nanosecond accuracy for electronic purpose

Really interesting and extensive answer. In my case, it is just a loop with: another_cycle: nop subs r0,r0,1 beq another_cycle Could it really change from one time to another ? Sure I have demonstrated this many times, in the pi the execution speed of that loop or even simpler without the nop, can ...
by dwelch67
Sun Jan 14, 2018 10:28 pm
Forum: Bare metal
Topic: understanding the arm timer
Replies: 1
Views: 200

Re: understanding the arm timer

no it means the interrupt from this peripheral fires when it reaches zero. this is fairly typical with timers, when the roll over they fire an interrupt, some count down some count up some count down to zero some count up to N and reload with zero, etc. You control the interrupt rate in this case wi...
by dwelch67
Wed Jan 10, 2018 3:58 pm
Forum: Bare metal
Topic: Timer with nanosecond accuracy for electronic purpose
Replies: 15
Views: 1042

Re: Timer with nanosecond accuracy for electronic purpose

I dont think the timer is your problem, there are a couple there already, it is the herky jerky nature of a pipeline, assuming you can keep the code in L1 then great, but it it bounces out to L2/DRAM then big performance hit, all accuracy is lost. Microcontrollers have a much better chance, similar ...
by dwelch67
Wed Jan 10, 2018 3:36 am
Forum: Bare metal
Topic: What can be realistically programmed in assembler today?
Replies: 39
Views: 1911

Re: What can be realistically programmed in assembler today?

While the everything that is possible is absolutely the answer, another interesting side effect is you can do MORE than you can with high level languages as you have no limitations other than the hardware/instruction set rules. The real question is knowing that anything that is remotely possible to ...

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