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by dwelch67
Sun Dec 17, 2017 5:51 am
Forum: Bare metal
Topic: [Solved] UARTs break
Replies: 8
Views: 235

Re: UARTs break

super simple way to test break and other framing errors is to feed the unit under test with a uart set for half or slower speed, write a 0x00 at 57600 into a 115200 unit under test and it looks like a break. feed other bit patterns and they look like various other things some legal some not pretty e...
by dwelch67
Sun Dec 17, 2017 5:49 am
Forum: Bare metal
Topic: [Solved] UARTs break
Replies: 8
Views: 235

Re: UARTs break

I have been forced to use break from time to time, it is a framing error by definition, the stop bit doesnt arrive at the right time and you need to re-sync. (think of it is a start bit that lasts longer than a character, or a bunch of zeros that stop through and beyond the stop bit) Each uart has i...
by dwelch67
Sun Dec 17, 2017 5:42 am
Forum: Bare metal
Topic: Pi won't start pianobar on boot
Replies: 1
Views: 80

Re: Pi won't start pianobar on boot

this is a bare metal forum
by dwelch67
Wed Dec 13, 2017 9:22 pm
Forum: Bare metal
Topic: [Solved] UARTs break
Replies: 8
Views: 235

Re: UARTs break

or just dont use the mini-uart if you want to detect break.
by dwelch67
Wed Dec 13, 2017 9:21 pm
Forum: Bare metal
Topic: [Solved] UARTs break
Replies: 8
Views: 235

Re: UARTs break

I dont use break much unless absolutely have to, problem is what is the definition for starters, how long does it have to be asserted to define a break? And then does the uart detect it at all, or detect just a framing error? Are you seeing a framing error and if so does the rx buffer have any data ...
by dwelch67
Mon Dec 11, 2017 9:50 pm
Forum: Bare metal
Topic: Reasoning about PWM for a DC Motor Driver
Replies: 2
Views: 168

Re: Reasoning about PWM for a DC Motor Driver

is there one universal answer? The pwm frequency is ideally faster than the motor/system can respond to, otherwise it sits there and oscillates or wiggles. But it doesnt want to be so fast that it is filtered out as noise. You can of course intentionally put your own filter in the system to turn it ...
by dwelch67
Mon Dec 11, 2017 9:44 pm
Forum: Bare metal
Topic: lwIP - A Lightweight TCP/IP stack
Replies: 20
Views: 4933

Re: lwIP - A Lightweight TCP/IP stack

skimming thread...depending on what you want to do you can bang out a UDP stack that cheats a lot in an afternoon or half an hour whichever. if i build a quicky client that I want to talk to in that I want to ask it questions, what is the temperature, send me some data, etc. I used fixed packet size...
by dwelch67
Mon Dec 11, 2017 9:33 pm
Forum: Bare metal
Topic: Dave Welche's bootloaders for RPi3 or other alternative
Replies: 16
Views: 662

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

generally I write and post the blinkers first increasing in complexity and/or rotating through possible timers in the device. unfortunately with the pi the leds are no longer directly tied to gpio pins (for the pi3) which means maybe now you need an led and a resistor and some wires. I usually write...
by dwelch67
Fri Dec 08, 2017 9:42 pm
Forum: Bare metal
Topic: Setting AUX_MU_LCR_REG for mini UART to 8 bit mode
Replies: 3
Views: 198

Re: Setting AUX_MU_LCR_REG for mini UART to 8 bit mode

If you are reading what I think you are reading is because the manual was wrong, took me a couple of hours as I didnt have a scope at the time. the pinned topic for baremetal has resources, in there there should be an errata thing on an elinux wiki page, this among many other bugs in the broadcom do...
by dwelch67
Thu Dec 07, 2017 9:41 am
Forum: Bare metal
Topic: Physical Address Mapping on the Pi3
Replies: 4
Views: 316

Re: Physical Address Mapping on the Pi3

you almost exactly have it right it is 47-32=15th bit Where does it say the 47th bit is the led? in some broadcom schematic we dont have access to. or in the linux port from broadcom that someone dug through to figure this out. There may be some documentation at this point that we have visibility to...
by dwelch67
Sun Dec 03, 2017 2:36 pm
Forum: Bare metal
Topic: Dave Welche's bootloaders for RPi3 or other alternative
Replies: 16
Views: 662

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

at the top of the baremetal forum there is a pinned thread that has a log of baremetal resources, look through those to find other solutions as well.
by dwelch67
Sun Dec 03, 2017 2:36 pm
Forum: Bare metal
Topic: Dave Welche's bootloaders for RPi3 or other alternative
Replies: 16
Views: 662

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

I have a raspberry pi three repo separate from the other, that is just raspberry pi three stuff including a bootloader. there are many alternatives folks keep coming up with other solutions, I even heard there is a way to change the rom in the part to have it pxe boot or something like that (permane...
by dwelch67
Thu Nov 16, 2017 3:41 pm
Forum: Bare metal
Topic: PL011 uart problems
Replies: 1
Views: 261

Re: PL011 uart problems

not sure what your question really is. If you want to use either of the uarts you have to set the function for the gpio pin to that peripheral to see anything come out (or in) and then of course program that peripheral to handle that task. What is the real problem you are having?
by dwelch67
Tue Nov 14, 2017 1:52 pm
Forum: Bare metal
Topic: How to enable timer interrupt on RPI3?
Replies: 2
Views: 332

Re: How to enable timer interrupt on RPI3?

Or is there yet another rev of pcb with the led on a gpio pin?
by dwelch67
Tue Nov 14, 2017 1:51 pm
Forum: Bare metal
Topic: How to enable timer interrupt on RPI3?
Replies: 2
Views: 332

Re: How to enable timer interrupt on RPI3?

the pi3's led is not directly connected to a gpio so unlikely that I would be blinking it in an example. The old pi1 examples shouldnt work across the board, with the pi3 you have different ways to boot it and how you handle interrupts is affected by that, are you booting aarch64, aarch32, HYP mode ...
by dwelch67
Tue Nov 14, 2017 1:46 pm
Forum: Bare metal
Topic: JLINK gdbserver and jtag debugging with Raspberry Pi 2
Replies: 20
Views: 3273

Re: JLINK gdbserver and jtag debugging with Raspberry Pi 2

reading the entire post, perhaps you want to start with a linux kernel that is single core and/or doesnt use all four cores, use the stock method for loading and running it. insuring the other one/two/three are not being used by linux. then from that linux or later using a custom bootloader you can ...
by dwelch67
Tue Nov 14, 2017 1:42 pm
Forum: Bare metal
Topic: JLINK gdbserver and jtag debugging with Raspberry Pi 2
Replies: 20
Views: 3273

Re: JLINK gdbserver and jtag debugging with Raspberry Pi 2

u-boot is just bloat that isnt needed, launching linux is fairly simple and the pi folks are doing that without the need for u-boot. if your goal is to run linux this is a bare metal forum. If you want to add a bootloader then thats fine, go ahead and add it. they have done all of the work, initiali...
by dwelch67
Mon Nov 06, 2017 3:15 am
Forum: Bare metal
Topic: Eclipse or other dev env, for cm3 written in assembly
Replies: 4
Views: 493

Re: Eclipse or other dev env, for cm3 written in assembly

The pi (none of them) has no debug interface you can simply download baremetal programs into and run them. This is not the target audience for this product, the target audience uses the thing as a computer with a usb keyboard, mouse and hdmi (or composite) display. If you want to work at this level ...
by dwelch67
Sat Nov 04, 2017 12:34 am
Forum: Bare metal
Topic: Eclipse or other dev env, for cm3 written in assembly
Replies: 4
Views: 493

Re: Eclipse or other dev env, for cm3 written in assembly

the CM3 is just another form factor, like a desktop pc vs a laptop vs a server. You can develop one program that runs on each, in this case it is even better as the chips are same or similar, they have multiple broadcom chips they have used, a very short list and the peripherals are the same, just t...
by dwelch67
Wed Nov 01, 2017 10:01 pm
Forum: Bare metal
Topic: JLINK gdbserver and jtag debugging with Raspberry Pi 2
Replies: 20
Views: 3273

Re: JLINK gdbserver and jtag debugging with Raspberry Pi 2

I think you mostly if not completely need to worry about generic armv7 and not raspberry pi specific, the raspberry pi specific part is that they dont have dedicated jtag pins for the ARM, so you need a little code to switch the gpio pins to the jtag function, then you let the debugger in, if the de...
by dwelch67
Sun Oct 29, 2017 1:52 pm
Forum: Bare metal
Topic: How to start bare metal progamming
Replies: 4
Views: 890

Re: How to start bare metal progamming

there are sadly two flavors of pi2 now, one with the armv7 and one with the armv8. you can absolutely start with one of these as well, I have examples as do many others. if you run without a config.txt file you get one of the cores booting at a known address, by using the right filename (kernel.img ...
by dwelch67
Sun Oct 29, 2017 1:42 pm
Forum: Bare metal
Topic: How to start bare metal progamming
Replies: 4
Views: 890

Re: How to start bare metal progamming

The pi-zero which is easier to come by, is also the older, simpler, broadcom chip. And the led is wired to gpio not elsewhere that takes more work. There is a sticky/thumbnailed topic a the top of the baremetal forum, lots of places to look to start baremetal programming. (as well as different opini...
by dwelch67
Thu Oct 19, 2017 12:37 pm
Forum: Bare metal
Topic: My doubts in understanding baremetal
Replies: 21
Views: 2261

Re: My doubts in understanding baremetal

That was my second draft, and should have just tossed it too. After sleeping on it was going to toss those replies anyway, didnt like how I had written them. Well understood that some mailboxes are special hardware not just memory. But calling it a "mailbox" doesnt automatically make it special hard...
by dwelch67
Sat Oct 14, 2017 12:27 pm
Forum: Bare metal
Topic: Reset specific core
Replies: 10
Views: 976

Re: Reset specific core

The ARM IP contains individual enables and resets per core, but it is up to the chip vendor as to what to do with these. I am still hoping that broadcom has an undocumented register with individual controls that the gpu used to start the arm. If the OP is not interested in actual resets but simply w...

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