radu
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Re: GPIO pinouts confirmed

Mon Nov 28, 2011 6:43 pm

I think it is best without pins. It\'s more flexible that way, and you can add the pins you want in a matter of minutes. It\'s not like most people need all of them anyway.

fdufnews
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Re: GPIO pinouts confirmed

Mon Nov 28, 2011 7:45 pm

[quote]Quote from Burngate on November 28, 2011, 17:20
I put this on the front-page replies-list but here might also be useful
[img]https://sites.google.com/site/burngateh ... /GPIOs.gif[/img]
[/quote]
Just a comment on your GIF it is not MIS0 et MOS1 but
MISO : Master In Slave Out
MOSI : Master Out Slave In

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abishur
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Re: GPIO pinouts confirmed

Mon Nov 28, 2011 7:47 pm

[quote]Quote from carlosfm on November 28, 2011, 17:57

If you want to interface directly to an audio dac chip, you need PCB and HDMI is useless. Don\'t even mention it.
Audio in HDMI is mixed with video. You need an AV amp to extract the digital audio and deal with HDCP, if present.

I\'ll check the audio quality on the analog audio jack too, but I doubt on the \"high quality\" on a portable device, don\'t get me wrong.
I\'m an audiophile, who usually builds and/or mods his own audio gear.
[/quote]

Well high quality != high def ;) The r-pi team has told us that they have chosen an audio jack that will be better than your run of the mill headphone jack on a mobile device... I believe the exact phrase used was CD quality?

But fortunately for you, it\'s not an issue since they are providing I2S. Lucky! ;)
Dear forum: Play nice ;-)

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Burngate
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Re: GPIO pinouts confirmed

Tue Nov 29, 2011 11:02 am

[quote]Quote from fdufnews on November 28, 2011, 19:45
Just a comment on your GIF it is not MIS0 et MOS1 but
MISO : Master In Slave Out
MOSI : Master Out Slave In[/quote]
Hmm ... I have a quotation I like: \"I\'m always right, even when I\'m wrong\"
In this case, due to the forum software, you now can see no evidence of my (former) ignorance!
Any other errors I\'ve made, please point point out.
And thanks.

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meltwater
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Re: GPIO pinouts confirmed

Tue Nov 29, 2011 12:23 pm

Thanks for the Pin out image!
Looks like the wiki\'s been updated too.

For me these GPIO points are what make the R-Pi interesting, it opens up all sorts of fun.

I\'d recommend a little patience before jumping straight in and wiring things to the board, drivers and protection circuits will probably be needed I am guessing. The lack of pre-fitted header will hopefully discourage this until clear instructions are available on what to do (if required), I hope will avoid blue smoke and upsets.

I assume if anyone wants to make use of the UART for instance then a MAX232 chip will be needed before connecting up etc.
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Nobody
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Re: GPIO pinouts confirmed

Tue Nov 29, 2011 1:23 pm

What I would like to know is:
\"How much current can the GPIO pins safely drain or source?\"

For an AtMega this figure is about 20mA per pin, but is the ARM as generous?

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FeersumEndjinn
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Re: GPIO pinouts confirmed

Tue Nov 29, 2011 9:45 pm

[quote]What I would like to know is:
\"How much current can the GPIO pins safely drain or source?\"
[/quote]

That is a question that I\'ve already posed and not yet received an answer to, so I\'d be interested in this as well. source current is critical, because even a few mA is enough to directly light an LCD, rather than using some form of bi-lateral switch to gain a higher source current.
Morrolan / FeersumEndjinn

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sylvan
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Re: GPIO pinouts confirmed

Tue Nov 29, 2011 10:01 pm

[quote]Quote from meltwater on November 29, 2011, 12:23I assume if anyone wants to make use of the UART for instance then a MAX232 chip will be needed before connecting up etc.[/quote]

Not true. It depends on what you need.

You are correct that the uart is not RS-232 serial. It is 0v to 3v serial. Not everybody needs RS-232 serial.

If all you need is 0-3v serial then you are good as is. My immediate need is ideal with 0-3v serial.

If you need RS-232 serial then you need a level shifter (like a MAX232).

If you need RS-422 or RS-485 serial then you need a line driver like the SP3485.

If you need fiber optic then you\'ll need a 3v to optical transceiver.

Etc.

(The RS-232 standard requires a transmitter to send a logic \'1\' as some voltage between -5v to -15v, and to send a logic \'0\' as a +5v to +15v level. Requirements for receivers are -3v to -25v for logic \'1\' and +3v to +25v for logic \'0\'. Typically a microcontroller uart will send a logic \'1\' as a voltage near their positive supply voltage (3.3v for the R-pi), and send a logic \'0\' as near 0v. They expect to receive similar.)

sylvan
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Re: GPIO pinouts confirmed

Tue Nov 29, 2011 10:08 pm

[quote]Quote from FeersumEndjinn on November 29, 2011, 21:45
[quote]What I would like to know is:
\"How much current can the GPIO pins safely drain or source?\"
[/quote]

That is a question that I\'ve already posed and not yet received an answer to, so I\'d be interested in this as well. source current is critical, because even a few mA is enough to directly light an LCD, rather than using some form of bi-lateral switch to gain a higher source current.[/quote]

This has been discussed a few times in \'relay\' related threads such as re. the Gertboard.

I\'ve not seen an official spec, but Gert is pretty close. As I recall, the numbers mentioned were in the range of 2-8 mA drive. I don\'t recall seeing a sink number yet. I\'m hoping to see an official number that\'s better. If not I guess I\'ll be wiring up some simple transistor switches, or perhaps an octal driver or two.

I\'d really like to 1) solder in a header(s), 2) plug in a connector with 16 LEDs, 3) make them all blink. :-)

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Gert van Loo
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Re: GPIO pinouts confirmed

Wed Nov 30, 2011 7:09 pm

[quote]I\'d really like to 1) solder in a header(s), 2) plug in a connector with 16 LEDs, 3) make them all blink.[/quote]
If that is your target you can definitely do that. Most LEDs these days do not need much current. If you go for \'low current\' ones you can be blinded using only 2 mA.
As to current source and sink: You have to be very careful of ground bounce and power noise. The GPIO pins can programmed with a rather high drive strength. Set them to max and you can drive a lot of current. Drive all 16 pins very fast and you might find your SD-card no longer work reliable: You have created enough power noise/ground bounce to influence the other GPIO pins. That is not a design flaw, it is just plain physics: In a package you can cram only so much copper and bond wires.

scologic
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Re: GPIO pinouts confirmed

Thu Dec 01, 2011 1:34 am

so the GPIO tx asnd rx are not rs232 then?

Getting confused - want toknow [ doesd the GPIO headers have RS232 or USB?

Donald Becker
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Re: GPIO pinouts confirmed

Thu Dec 01, 2011 2:58 am

My interpretation is that the GPIO header has logic-level serial I/O.
That\'s basically \"RS232\", but requires inverting input and output drivers.

An output driver converts a 0V output to about +9V, and a 3V output to about -9V. It does the reverse on the Rx side, cleaning up noise and protecting against over-voltage.

I find that bluetooth serial modules, available on FleaBay for about $10, are the most convenient way to use logic-level serial for debugging-type communication. But if you want to control serial devices you\'ll need to buy an output driver (usually a Maxim chip which generates its own +12V/-12V supplies) on a small board for about $20.

Nexy
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Re: GPIO pinouts confirmed

Fri Dec 02, 2011 1:15 am

Please forgive me wandering off topic to address something said earlier in the thread...

[quote]Quote from carlosfm on November 28, 2011, 17:57
If you want to interface directly to an audio dac chip, you need PCM and HDMI is useless. Don\'t even mention it.
Audio in HDMI is mixed with video. You need an AV amp to extract the digital audio and deal with HDCP, if present.
[/quote]

I might have misunderstood you, but are you suggesting you need a full HDMI AV Amp to extract audio from HDMI? Because you don\'t. I\'ve got a Mux-HD (which admittedly was damned expensive when I bought it) but you can pull the audio out of HDMI and convert it to VGA (or component) for £25 (plus US -> UK power adapter, probably just a physical 99p from Asda one though.)

http://www.ebay.co.uk/itm/HDMI-VGA-RGB- ... 874wt_1185

You can get them from the UK for £33.
http://www.ebay.co.uk/itm/HDMI-VGA-YPbP ... 0835855537

That\'ll give you SPDIF out. The wording is slightly ambiguous as to if it strips out HDCP or not. Not sure if that\'ll meet your needs or not, it\'s primarily just to clarify/correct what you\'d said.

sylvan
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Re: GPIO pinouts confirmed

Fri Dec 02, 2011 7:17 pm

[quote]Quote from scologic on December 1, 2011, 01:34
so the GPIO tx asnd rx are not rs232 then?

Getting confused - want toknow [ doesd the GPIO headers have RS232 or USB?[/quote]

Sorry for the confusion.

The GPIO TX and RX are not RS-232. They are not USB. They are logic level (in this case 3volt logic).

As another poster mentioned earlier, the GPIO TX and RX are logic level serial. That is different from RS-232 serial. (RS-232 is but one of many different serial standards.)

To connect the GPIO TX and RX to an RS-232 serial device you need a 3volt logic to RS-232 line driver. This will convert the logic level serial to use and accept the correct signal voltages required by RS-232.

Does that help or still leave more questions?

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FeersumEndjinn
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Re: GPIO pinouts confirmed

Fri Dec 02, 2011 7:34 pm

I think I\'m correct in saying that RS-232 is 12v logic?
Morrolan / FeersumEndjinn

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mogen317
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Re: GPIO pinouts confirmed

Fri Dec 02, 2011 7:44 pm

Let me repost this question.

[quote]Quote from NoSuchNick on November 28, 2011, 09:36
Thank you for the pinout liz, there goes my productivity for the day ;)
Just to add to all the other questions:
Can we use the 5V pin to power the r-pi or are there diodes or something similiar that would prevent that?[/quote]

Can a conditioned 5v source such as a battery with voltage regulator be connected to the 5v and GND GPIO pins to power the Raspberry Pi?

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Gert van Loo
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Re: GPIO pinouts confirmed

Fri Dec 02, 2011 8:00 pm

\"I think I\'m correct in saying that RS-232 is 12v logic?\"

If I recall the standard says (many years since I read it):
The range is from +5v and -5 to about +15V and -15V.

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FeersumEndjinn
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Re: GPIO pinouts confirmed

Fri Dec 02, 2011 8:09 pm

[quote]Quote from Gert van Loo on December 2, 2011, 20:00
\"I think I\'m correct in saying that RS-232 is 12v logic?\"

If I recall the standard says (many years since I read it):
The range is from +5v and -5 to about +15V and -15V.
[/quote]

Ahh many thanks - I felt I was in the right ballpark but it didn\'t quite feel right. :)
Morrolan / FeersumEndjinn

"And the lord God said unto John, 'Come forth and receive eternal life', but John came fifth and won a toaster."

Willakan
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Joined: Mon Oct 31, 2011 3:49 pm

Re: GPIO pinouts confirmed

Thu Dec 08, 2011 4:11 pm

Is the I2S bus limited by what the on-board audio can manage (in that PulseAudio or whatever other audio engine in your chosen distribution potentially downsampling everything before it ever gets anywhere near the bus to suit the abilities of the designated output device - presumably 16bit/48khz max) or can you get 24 bit audio at higher sampling frequencies off it?

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