RasPi power requirements overstated?

That should work fine, twisted-pair ethernet includes galvanic isolation, so sharing the power supply won't cause any shorts or ground loops

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Reply to
Jasen Betts
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Interesting. I'll look into it. Thanks.

Another Dave

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Another Dave

I demand that snipped-for-privacy@ncf.ca may or may not have written...

Are you sure about that? Every old home computer which I've seen has RF output (and usually tuned to UHF channel 36, clashing nicely with video recorders). Some may also have had composite outputs, but not necessarily phono type.

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Reply to
Darren Salt

the band chosen depends on where you are, my ZX81 used channel 1 (45.25 MHz) IIRC (NZ has an unusual frequency plan)

most TVs made after the VCRs became affordable have composite inputs

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Reply to
Jasen Betts

You're right.

I was basing my identification on this:

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Strangely, It starts off as RTL2838 (see the before results) but transmutes into RTL2832 after the driver has been installed.

Curious.

Another Dave

Reply to
Another Dave

On 12/04/2013 16:16, Another Dave wrote: []

I'm glad it worked out - but credit the information I read - I was just the messenger in this case.

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Reply to
David Taylor

Yes, buy since the topic is 'power requirements', let's continue consideriing the MINIMAL requirements. Ie. rPi displaying on a PC which has no ETH*/networkCard. == Again, the first guess at just replacing the ETH-connection with a serial/ RS232 one fails becauase the rPi's 3.3V output is incompatible. So am I wrong that the 3.3V of the rPi's GPIO should be able to drive a PC's standard centronics/ParPort's few input lines?

==TIA.

Reply to
Unknown

Eh? What cave are you living in?

Really, who cares. This problem has been solved. Get Ethernet.

Gordon

Reply to
Gordon Henderson

rPi output is UART not RS232.

Adding a RS232 converter, or USB (on PC) to UART (TTL/3V£) has been solved.

You must be living in the 1980's if you think in terms of printer ports.

It is difficult to get a PC/Laptop without USB or Ethernet for last 10 years most desktops these days have RS232 level comm ports.

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Paul Carpenter          | paul@pcserviceselectronics.co.uk 
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Reply to
Paul

I am not sure that is actually true..

looking at a typical budget PC mb it has one parallel port and one serial HEADER.

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but Ethernet and USB are built on as standard and socketed right off the board.

The high price of cannon style multipin connectors means there is a huge incentive to not supply them

USB is far cheaper and far lower spec.

and even an 8 pin RJ45 is a cheap beast by comparison.

AS a hardware designer for many years, te costs of 'hardware' as opposed to circuitry were usually the major element in costs.

in the case of the Pi, by leaving out most of that, and the case and power supply, you end up with a cheap selling price.

Adding a case, PSU, keyboard, mouse and screen and enough sockets to make it a 'PC' would mean it was no cheaper than a budget PC is anyway..

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Reply to
The Natural Philosopher

You probably meant to say: have NO RS232 level comm ports. And no parallel printer port, either.

Reply to
Rob

You'll often find a COM port header on the motherboard, so all you need is a back-panel adapter and they are cheap enough. Many of the serial peripherals for the RPi are 3.3 V in any case, so no further adapter is needed.

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David Taylor

Can anyone say what the ACTUAL power demand of the Pi is when the OS is idling? I have an application in a battery-powered device that would be suitable for the Pi or Beagle Bone, but all I've been able to find on the Pi is the MAXIMUM power supply requirement, not the demand in actual operation. I'm most concerned with the demand when the ethernet is operational, but not transferring data very often, and nothing else connected except some GPIO pins.

The Beagle Bone has a published spec of 170 mA at 5V in that condition. Anybody got a number for the Pi?

Thanks,

Jon

Reply to
Jon Elson

Around 400mA according to these:

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Reply to
Rob Morley

I said 'most'

All the low end Zoostorm, Acer, Fujitsu, HP desktops I have looked at over last 6 months have PS2 port(s), at least 1 serial as well as USB and ethernet connectors. Mainly so places with POS and other applications like serial weighing machines will work as USB to serial with modem control does not cut it.

MOST people these days buy boxes and dont build desktops, no real savings in doing that.

So what I said MOST, and anyway they buy the stacking connector blocks for serial and VGA/DVI for most motherboards to reduce PCB area and are standard parts on MOST motherboards.

......

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Reply to
Paul

NO I did not lets start with

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Warranty-Upgrade

I did NOT say laptop, media centre, small form factor or all-in-one I said desktop, which a lot have the connector on back or have the header inside. The header is easy to add the standard cable to, and very cheap.

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Paul Carpenter          | paul@pcserviceselectronics.co.uk 
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Reply to
Paul

Sorry the adapter is to bring out RS232 signal levels NOT 3V3 levels, so an adapter is needed.

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Paul Carpenter          | paul@pcserviceselectronics.co.uk 
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Reply to
Paul

I've built two mid-level machines, and one entry level one in the last few months; they all used Intel Core ix capable MB's.

All three had a parallel port on the back, and an RS232 header on the board.

Chris

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Reply to
Chris Whelan

You miss my point - for the PC the RS-232 levels are already there, even though most PCs don't have the port any more it's relatively easy to fix that.

Yes, for the RPi you need an adapter for true RS-232 levels, but many RPi and Arduino already use 3 V serial, so no level shifting is required. In practice, a couple of resistors may be enough (that's what I've used).

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Reply to
David Taylor

It appears that not all mini USB phone chargers, even OEM ones are necessarily 5 volt.

I have one here that was supplied with a Amoi WP-S2 aka "3" Skypephone S2. It is rated at 5.25V 600mA. Now I don't know if that quarter volt would harm a Pi, probably not, but there may be other examples that are even higher.

I notice that some phone chargers are described as fast chargers, I imagine this is an example of one.

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Graham.

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