<naobsd>
if you already can put a char, you may write code which prints "where am I?"
<naobsd>
if KERNEL_IMG doesn't work as you want, you may write code which copy itself from 0x60408000 to where you want
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<naobsd>
hmm... may I delete linux-rockchip-3.0 on github? I guess no one use it so it should be ok... I want to redo everything ;)
<naobsd>
because there is rockchip source with their history
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<ganbold_>
naobsd: since I can print one char I can narrow down where it stops printing, so I know the loader loads freebsd kernel and it runs at least :)
<naobsd>
ganbold: very nice :)
<naobsd>
ganbold: my rkcrc is BSDL, feel free to import
<naobsd>
ls
<naobsd>
oops
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<arokux2>
hipboi: do you think a 12V power supply will be ok for radxa? On the wiki I see 5V.
<lunra>
If it's like the cubieboard, there is no voltage regulator, and you MUSt supply clean 5V to it
<lunra>
(and it probably is - the board is marked DC-5V/2A on the silkscreen image on the main page)
<lunra>
With power supplies, the 'A' (amps) is a maximum drain amount (which means you can have a higher 'A' value than specified, however, voltage ('V') is absolute, and the voltage must be what is specified
<arokux2>
thanks lunra ugh.. different boards, different power supplies.. is there a power supply with multiple outputs so that the voltage is configurable per each?
<lunra>
feed it 15V DC at a decent amp capacity, then put two of them in parallel with the grounds connected, tune the precision potentiometer on the board until one is 12V (or a little bit over, read your other board's spec), and 5V for the other one
<arokux2>
6-16V input power supply, noise immune design
<lunra>
wow, I have no idea why they put a regulator on-board
<lunra>
well, depending if the regulator on the olimex board can handle an extra 2A of current, you can probably take USB power from that board to power the radxa
<lunra>
USB isn't specced to supply 2A, but the voltage rail should be directly connected to a 5V regulator
<lunra>
That 12V AC adapter has a max drain of 0.5A, so it's 12 * 0.5 = 6 Watts, probably not going to work
<lunra>
IIRC the rk3188 boards out today draw around 3W, and that A20 is probably similar, and regulators are not 100% efficient
<lunra>
You could use a PC power supply, just use a low-wattage one because the high-wattage ones are inefficient when under-drained
<lunra>
Sadly these embedded computers can still take some electronics knowledge to get to work, which is a shame because that might reduce the number of capable software developers who can use the platform.
<lunra>
please note, I take no responsibility for the information I gave.
<arokux2>
lunra: thank you very much for this info, very kind of you!
<lunra>
Hmm, IMO it's overpriced, I doubt it is as good as they seem to claim it is
<lunra>
their software might also only run on Winblows
<arokux2>
lunra: that is why I try to find something like this and cheaper.. maybe you know it?
<lunra>
oh, has serial and Bluetooth control, so someone could probably make a controller for it
<lunra>
Sorry, I tend to make my own things like this
<lunra>
sadly it's expected that people who will need these type of power supplies will already know how to build them, but I don't think that's fair
<lunra>
you can probably just twist wires together and cover them in tape instead of having to solder, if you don't care about reliability or safety. My stuff tends to be built that way, sometimes I'll fix it, other times I'll leave it alone, other times I'll take it all apart
<arokux2>
lunra: although I am learning basics of electronics now, I do not want to mess up with power supplies, seems dangerous to a novice :)
<lunra>
But, you can just use two different AC adapters (in fact you can't use the same one, most of the time, because you run out of power)
<lunra>
AC power can be quite dangerous, but as long as the AC adapter isn't malfunctioning, 18V and below are pretty harmless. I definitely wouldn't want to buy a device that was built the way I build things...
<arokux2>
lunra: yeah, I can use several power supplies. I just don't like this inflexibility :)
<lunra>
just don't... lick the power supply or anything :)
<lunra>
I used to have a friend that used to lick power supplies to see if they were working... 'used to'
<lunra>
Just kidding, he's fine. But it's a bad idea.
<arokux2>
:D
<lunra>
Are you building anything in particular, or just want to have both computers?
<arokux2>
lunra: no, now I have two boards: Mele A1000 (Allwinner A10) and Radxa, soon I'll have another two: Cubietruck and Olimexino-A13. and just thinking about the fact I will need 4 x power adapters makes me sad :)
<arokux2>
lunra: I'd like something like usb hub, you know? it plugs into master plug and has multiple outputs.
<lunra>
Ah. I have two cubieboards and an mk802 clone (ak802) (Allwinner A10). I have a beagleboard-xM too, but it doesn't work anymore :( (it suddenly died while running a minecraft server, now it only sends garbage to the serial port)
<lunra>
It's difficult because these devices do actually use quite a bit of power
<arokux2>
lunra: quite a bit? hm.. several Watts each, kitchen appliances use much much more. or I have missed something?
<lunra>
if you have 4 boards, it's like 25 watts at peak (rough estimate based around ~5W/board), which isn't much compared to an x86 PC or even x86 laptop, but it's more than most devices that run at 5V
<lunra>
Of course you can have 1000W microwave ovens and stuff like that, but they run at mains voltage (110V for United States, 240V here in Australia)
<lunra>
it's harder, but still not that hard, to get an efficient 5V power supply in this wattage range
<lunra>
the 12V rails in PC power supplies are the most heavily loaded, because it's cut down to ~1.2V on the motherboard for the CPU, and the GPU does something similar
<lunra>
It's due to Ohm's Law, V = IR (which can be rearranged to I = V divided by R), where V is volts, R is resistance in ohms, and I is current in Amps. At low voltage, a resistance results in a lower current, but at a higher voltage, the same resistance results in a higher current than the low voltage
<lunra>
And because wires have resistance, it's not good to try to drain a lot of current at 5V over long wires
<lunra>
It's fine for this ~30W wattage range, but the market doesn't produce power supplies for this
<arokux2>
lunra: thanks for the explanation. I was looking for a small electronics project to work on, so I learn on the go. do you think designing something like this power supply (with multiple outputs and enough wattage) could be something like this?
<lunra>
I'm not an expert, just a hobbyist, so be careful with what I say :)
<lunra>
Hm, well, I wouldn't recommend making your own connection to the house power supply
<lunra>
So you'd first have to find an AC adapter that provided enough wattage
<lunra>
Then it's fairly simple to use pre-made boards to produce the voltages you want
<lunra>
for each board you can use a different regulator board, but don't try to use two regulators for the same board in parallel. I can't remember why you're not supposed to do this, but it's something like causing voltage drops and spikes
<arokux2>
lunra: for now, I'd just buy several power adapters...
<lunra>
also, boards must have the same ground reference (connect all grounds together). This is because voltage is just a difference in electronic potential between two points, so a '12V wire' is compared to ground, at 0 Volts, to produce 12 volts
<arokux2>
lunra: yep :)
<lunra>
what is '0 volts' to your circuit might be 12 kilovolts above the floor of your house, even
<lunra>
oh, you do know this? Sorry, I wasn't trying to imply that you didn't know, but just explain it in case you didn't
<lunra>
Don't be tempted to use the older linear regulators... ever. They are really really inefficient, and often they will get hotter than the entire rest of the circuit
<lunra>
heat is of course wasted electricity
<arokux2>
lunra: from Hydra specs: ~12 watts available per output at any voltage level
<lunra>
Yeah, the Hydra seems good, just a bit pricy.
<lunra>
If you're willing to spend that much, and aren't bothered by the fact that it seems it can ONLY be computer controlled, it could be good
<arokux2>
lunra: no, it'd cost much more then ALL the boards I have :)
<arokux2>
lunra: but I do not understand something.. it requires +5.0 V to +14.0V power supply. but what about wattage? you can "generate" any wattage you want on the output?
<lunra>
Wattage remains the same, it can only get lower from a regulator
<lunra>
You must supply more wattage before the regulator than you require after the regulator
<arokux2>
lunra: so the AC supply to Hydra must be 25W or so?
<lunra>
Yes
<lunra>
It comes with an AC adapter, it seems, but it has a US plug
<lunra>
(the one it comes with is 36W, 12V, 3A)
<lunra>
but it's not AC that it is supplied with, it's DC
<lunra>
it goes, wall -> AC adapter -> hydra -> radxa/cubietruck/A1000/olimexino-A13
<arokux2>
lunra: are you sure it is supplied with AC? from data sheet: Hydra is a DC-DC converter
<lunra>
no, I said that it is supplied with DC
<lunra>
< lunra> but it's not AC
<lunra>
:)
<arokux2>
lunra: ah, right, sorry.
<lunra>
no problem, just be careful when you actually hook it up
<arokux2>
lunra: I'm just curios now to learn how it is done, not yet going to something.
<arokux2>
lunra: yeah, there are several pages like this
<arokux2>
lunra: last question that I have.. how do I know what is power output of a PSU of PC?
<lunra>
It -should- be documented in the box that the PSU came in, or on the PSU itself
<lunra>
the pinout of the connector should be used, not the color of the cable, as well
<lunra>
Many sellers even document the power rail amp limits on the product page
<lunra>
(that's the ideal way)
<arokux2>
lunra: ok, thanks!
<lunra>
Well, I'm off to bed. Good luck arokux2 :)
<arokux2>
thanks lunra
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<ganbold_>
naobsd: is it possible to change "KERNEL_IMG: 0x60408000" ?
<AstralixNB>
You must patch the bootloader for that
<ganbold_>
AstralixNB: how to do that?
<AstralixNB>
First you should check parameters file, if you can set the address there.
<AstralixNB>
but if not you need to decrypt the bootloader, decompile its parts and patch probably flash_boot section to your needs. Then encrypt it and flash it
<ganbold_>
AstralixNB: do we have these information on wiki or somewhere?
<ganbold_>
AstralixNB: how is u-boot status? I mean, u-boot development supporting RK3188? I heard you are working on it
<AstralixNB>
These infos are pretty complicated and sofor not on the wiki.
<AstralixNB>
And as bootloader is encrypted, it is somehow problematic about being legal to break the encryption
<arokux2>
AstralixNB: mm.. not sure now. but I cannot find any parts like this
<arokux2>
maybe I'm missing a keyword..
<AstralixNB>
There are normally no such things as you need to provide enough power
<AstralixNB>
Let's say if you like to charge four tablets then you need to provide up to 2A per plug. in that case you neded a AC/DC charger for up to 8A
<arokux2>
AstralixNB: not really, but this is the only thing I was able to find. now the question is if there are cables with coaxial connectors on one side, and such that will fit into this power strip
<AstralixNB>
Why not. Cut the cables, shield is GND and inner cable is +
<arokux2>
yeah, can be done that way, but will be nice just to to have a plug :)
<AstralixNB>
what do you want to supply?
<arokux2>
several boards.. some need 5V and some 12V, I want to come up with flexible solution instead of one power supply per each
<AstralixNB>
Then you need quite a good PSU
<AstralixNB>
Without you might face some interference
<arokux2>
somehow it is very complicated... maybe it is better to stick to normal AC-to-DC adapters
<Astralix>
Yes XP does have different models with dual-output and even with tripple or standby output.
<arokux2>
Astralix: to set up a DC power stripe is somehow very difficult. I didn't expet it to be that way. I've thought there might be some existing solutions to buy.
<arokux2>
why we do not have DC 5V and DC 12V sockets at our homes, it could be so practical!
<Astralix>
No, it wouldn't
<Astralix>
The lower the voltage, the higher the current
<arokux2>
is it bad?
<Astralix>
The higher the current, the more copper for your cables, as you need to provide low resistance over long ways
<arokux2>
ok, for transportation, but in homes? there could be one AC2DC, instead each and every device has one. isn't it a waste of resources?
<Astralix>
I am pretty sure it is not.
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<arokux2>
Astralix: ok, I have notebook, external HDD and a bunch of other devices, each of those has AC2DC converter. why not make this converter central?
<Astralix>
To provide 100W for your LED TV, you need 0.75mm diameter cables at 230V
<Astralix>
Ok, we take 100W for a Notebook.
<Astralix>
this will be 8A on 12V
<Astralix>
Ok that is peak, but if you have small cables for these 8A the Voltage will drop far below 12V and you Notbeook will fail in high load conditions
<Astralix>
you can calculate the voltage drop if you check specific resistancew of copper and take for instance a distance from cellar where you store your Master DC/DC and the possible wall plug in your living room
<Astralix>
but this IRC is not for electrical discussions I think
<Astralix>
you can check mikrocontroller.net for discussions like this
<arokux2>
Astralix: so the converter must be as close as possible to a device. this is unfortunate.
<Astralix>
yes it sould be
<arokux2>
Astralix: yes, you're right, this is off-topic here.
<arokux2>
thank you very much Astralix
<Astralix>
welcomed
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