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by dwelch67
Wed Dec 27, 2017 1:19 am
Forum: Bare metal, Assembly language
Topic: Drive up to 20 stepper motors (28byj-48)
Replies: 15
Views: 3427

Re: Drive up to 20 stepper motors (28byj-48)

steppers can be driven either way, tend to be able to go around and around as many times as you want. servos tend to not spin all the way around, used for things like controlling the rudder on an rc plane or boat.
by dwelch67
Mon Dec 25, 2017 4:07 am
Forum: Bare metal, Assembly language
Topic: Drive up to 20 stepper motors (28byj-48)
Replies: 15
Views: 3427

Re: Drive up to 20 stepper motors (28byj-48)

too broad at this point, depends initially on the driver you plan to use, what is the interface, how many motors can it control, etc. do they all have to be powered and hold their position or can you put a relay board or some flavor of mux such that you have one driver and switch only one motor in a...
by dwelch67
Wed Dec 20, 2017 2:32 pm
Forum: Bare metal, Assembly language
Topic: Config.txt over_voltage option Bare metal
Replies: 2
Views: 708

Re: Config.txt over_voltage option Bare metal

I dont know the board design, but would recommend against messing with voltages, that doesnt often work out well, in some cases you can tweak but you go to low and logic just stops working. the windows are generally very tight. you want to save power lower the clock rates for the processor and ddr i...
by dwelch67
Tue Dec 19, 2017 7:06 pm
Forum: Bare metal, Assembly language
Topic: Run interrupts on raspberry pi 3
Replies: 9
Views: 2515

Re: Run interrupts on raspberry pi 3

I probably didnt bother with the pi3 led (maybe someone will prove me wrong with my own examples), I did try to find it over i2c, but mailboxes arent interesting to me, talking to the gpu. If anything I have boards with leds and resistors i can use on any gpio pin, but that doesnt serve as a good ex...
by dwelch67
Tue Dec 19, 2017 7:02 pm
Forum: Bare metal, Assembly language
Topic: [Solved] UARTs break
Replies: 12
Views: 2922

Re: [Solved] UARTs break

Nope, just stating that a break is a framing error. uarts are not all built equal (although a lot like/try to clone the 16550). So if there isnt a specific break detect and/or it doesnt work then perhaps a combination of framing error and rx data maybe you can assume break from that. I have not look...
by dwelch67
Tue Dec 19, 2017 12:56 am
Forum: Bare metal, Assembly language
Topic: Run interrupts on raspberry pi 3
Replies: 9
Views: 2515

Re: Run interrupts on raspberry pi 3

if booted in aarch32 it starts in supervisor mode, but the bootstrap that the gpu places if you let it (no config.txt or not overriding the boot in config.txt), you get HYP mode or at least for while now but who knows maybe one day they will change. So you can 1) let it boot stock into hyp mode, lea...
by dwelch67
Sun Dec 17, 2017 5:51 am
Forum: Bare metal, Assembly language
Topic: [Solved] UARTs break
Replies: 12
Views: 2922

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, Assembly language
Topic: [Solved] UARTs break
Replies: 12
Views: 2922

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, Assembly language
Topic: Pi won't start pianobar on boot
Replies: 1
Views: 447

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, Assembly language
Topic: [Solved] UARTs break
Replies: 12
Views: 2922

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, Assembly language
Topic: [Solved] UARTs break
Replies: 12
Views: 2922

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, Assembly language
Topic: Reasoning about PWM for a DC Motor Driver
Replies: 2
Views: 732

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, Assembly language
Topic: lwIP - A Lightweight TCP/IP stack
Replies: 20
Views: 7946

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, Assembly language
Topic: Dave Welche's bootloaders for RPi3 or other alternative
Replies: 18
Views: 3308

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, Assembly language
Topic: Setting AUX_MU_LCR_REG for mini UART to 8 bit mode
Replies: 3
Views: 654

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, Assembly language
Topic: Physical Address Mapping on the Pi3
Replies: 4
Views: 2807

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, Assembly language
Topic: Dave Welche's bootloaders for RPi3 or other alternative
Replies: 18
Views: 3308

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, Assembly language
Topic: Dave Welche's bootloaders for RPi3 or other alternative
Replies: 18
Views: 3308

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, Assembly language
Topic: PL011 uart problems
Replies: 1
Views: 669

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, Assembly language
Topic: How to enable timer interrupt on RPI3?
Replies: 2
Views: 1268

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, Assembly language
Topic: How to enable timer interrupt on RPI3?
Replies: 2
Views: 1268

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, Assembly language
Topic: JLINK gdbserver and jtag debugging with Raspberry Pi 2
Replies: 21
Views: 7351

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, Assembly language
Topic: JLINK gdbserver and jtag debugging with Raspberry Pi 2
Replies: 21
Views: 7351

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, Assembly language
Topic: Eclipse or other dev env, for cm3 written in assembly
Replies: 4
Views: 956

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 ...

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