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by dwelch67
Thu Feb 01, 2018 10:36 am
Forum: Bare metal, Assembly language
Topic: starting to make an os for rpi
Replies: 18
Views: 3742

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, Assembly language
Topic: Using Dave Welch's bootloader07
Replies: 7
Views: 1295

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, Assembly language
Topic: Using Dave Welch's bootloader07
Replies: 7
Views: 1295

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, Assembly language
Topic: Mini UART dropping data
Replies: 4
Views: 984

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, Assembly language
Topic: Mini UART dropping data
Replies: 4
Views: 984

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, Assembly language
Topic: Understanding of RPi3 addresses
Replies: 3
Views: 1077

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, Assembly language
Topic: Baking Pi Update List
Replies: 12
Views: 2119

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, Assembly language
Topic: Baking Pi Update List
Replies: 12
Views: 2119

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, Assembly language
Topic: Up to date way to debug Bare Metal
Replies: 6
Views: 1780

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, Assembly language
Topic: Difference between Interrupts in x86 and Exceptions in Arm
Replies: 5
Views: 1396

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, Assembly language
Topic: JTag for Pi 3
Replies: 10
Views: 5048

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, Assembly language
Topic: JTag for Pi 3
Replies: 10
Views: 5048

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, Assembly language
Topic: Raspberry Pi 3 Kernel Development with Broadcom 2835
Replies: 2
Views: 669

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, Assembly language
Topic: General Approach for a Minimal Kernel in ARM
Replies: 2
Views: 707

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, Assembly language
Topic: Timer with nanosecond accuracy for electronic purpose
Replies: 15
Views: 5697

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, Assembly language
Topic: understanding the arm timer
Replies: 1
Views: 680

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, Assembly language
Topic: Timer with nanosecond accuracy for electronic purpose
Replies: 15
Views: 5697

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, Assembly language
Topic: What can be realistically programmed in assembler today?
Replies: 39
Views: 8217

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 ...
by dwelch67
Tue Jan 09, 2018 3:05 am
Forum: Bare metal, Assembly language
Topic: Hello world! bare metal boot of PI Zero, ASM + C
Replies: 2
Views: 2327

Re: Hello world! bare metal boot of PI Zero, ASM + C

vectors.s .globl _start _start: mov sp,#0x8000 bl notmain hang: b hang .globl PUT32 PUT32: str r1,[r0] bx lr .globl GET32 GET32: ldr r0,[r0] bx lr .globl dummy dummy: bx lr notmain.c extern void PUT32 ( unsigned int, unsigned int ); extern unsigned int GET32 ( unsigned int ); extern void dummy ( uns...
by dwelch67
Tue Jan 09, 2018 2:59 am
Forum: Bare metal, Assembly language
Topic: Hello world! bare metal boot of PI Zero, ASM + C
Replies: 2
Views: 2327

Re: Hello world! bare metal boot of PI Zero, ASM + C

absolutely I have examples for pi-zero look in the boards/pi-zero directory or look at the standalone repo https://github.com/dwelch67/raspberrypi-zero
by dwelch67
Mon Jan 08, 2018 9:57 pm
Forum: Bare metal, Assembly language
Topic: Powering CPUs on/off in RPi3
Replies: 11
Views: 3128

Re: Powering CPUs on/off in RPi3

nCPUPORESET[CN:0]

nCORERESET[CN:0]

as with other arm cores that came before there are individual reset lines per core that the chip vendor controls. its a chip vendor question not an arm TRM question.
by dwelch67
Mon Jan 08, 2018 3:50 pm
Forum: Bare metal, Assembly language
Topic: Practical question: RPi SD card reader worn
Replies: 5
Views: 828

Re: Practical question: RPi SD card reader worn

I agree, go with a bootloader. the original pi something about that full sized slot would crack a corner of my sd card adapters, ran through a number of them (before having a solid bootloader). later adafruit made a pcb flush mount micro sd adapter that would slide in and that problem got solved.
by dwelch67
Sun Jan 07, 2018 1:25 pm
Forum: Bare metal, Assembly language
Topic: Dave Welche's bootloaders for RPi3 or other alternative
Replies: 18
Views: 3780

Re: Dave Welche's bootloaders for RPi3 or other alternative

This is very typical for uarts, sadly on a platform like this it doesnt have to be this way they could have the uart shifters run off of the 100mhz (or whatever) reference clock not the PLL clock, and or they could allow for a PLL tap for the peripherals. which the system clock at 250MHz should have...
by dwelch67
Sun Jan 07, 2018 1:21 pm
Forum: Bare metal, Assembly language
Topic: Powering CPUs on/off in RPi3
Replies: 11
Views: 3128

Re: Powering CPUs on/off in RPi3

I am still curious about this as well, I would hope it is just an undocumented register and they flip on all four at once. (and have four sets of controls) Why? Because it is there, like why climb the mountain. In part if you are not using the core why have the other three be beating on the cache/dr...
by dwelch67
Fri Jan 05, 2018 6:39 pm
Forum: Bare metal, Assembly language
Topic: Access GPIO with assembly gives segmentation fault
Replies: 2
Views: 820

Re: Access GPIO with assembly gives segmentation fault

this is a baremegal forum, looks like you are writing a user application on an operating system (by definition not bare metal). there are many examples and we can help with baremetal, but hit up one of the other forums for application work (hint google mmap())

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