garyamort
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Re: Standardized Expansion Header

Fri Oct 28, 2011 6:47 pm

For a future developer revision, what I'd like to see is a standardized expansion header with as many pins as possible and focusing on the ones used most in the wild.

As I understand it, the current plan is to bring them all out to a strip, but then we will need to add the pins/connections there. Which seems to me to be a good choice for the initial production as there is no way to predict how it will be used.

Ideally this should be compatible with one of the existing SoM devboards so existing sensor modules and such can be used.

On the onehand, I'd really actually prefer it to just have the bare layout and to allow for third parties to produce the conversion board connectors. However, having an "official" layout makes it to a large extent much easier for developers to all develop the same functions.

At the end of the day though, I'd say there is no point in trying to figure out what is should be until there actually are Pi's and projects out there.

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abishur
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Re: Standardized Expansion Header

Fri Oct 28, 2011 7:26 pm

It's been said that the header pins have been deliberately designed to encourage people to really know what they're doing before blindly attaching headers or devices to the board. Still, I'm sure it won't be too long before we see both official and unofficial expansion boards to take advantage of the pins ;)
Dear forum: Play nice ;-)

BarryK
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Re: Standardized Expansion Header

Thu Dec 08, 2011 1:11 am

I know that there has been much discussion about the header pins and why the beta boards will not have them pre-soldered on. Like, some people want 90 degree angle, others want them underneath the board.

But, I just can't help feeling this was a bad decision. I think that the final release boards should have header pins, sticking straight up, on top-side of board.

There could be lots of adaptor boards getting developed and offered for sale, and standardised header pins is important -- and equally important, users should not have to do any soldering.

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daveg
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Re: Standardized Expansion Header

Thu Dec 08, 2011 1:50 am

Maybe later revision will have the header already fitted, the reason they may not be on the initial release could be related to cost. (Speculation on my part I might add).

If you want to use the I/O ports it really isn't that difficult to solder a header like that on, it is quite large compared to some of the surface mount components elsewhere on the board.

Point3Forever
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Re: Standardized Expansion Header

Thu Dec 08, 2011 2:58 am

From what I understand it's easy to fry the SoC by shorting the wrong pin. Also, those who are messing around with hardware are likely to know how to solder (it's a good thing to learn anyways).

I personally prefer having the pins the way they are. I do have some projects in mind that would require odd pin configurations (pi-on-pi for instance).

Sancho
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Re: Standardized Expansion Header

Thu Dec 08, 2011 8:07 am

Yeah, GPIO for the most fun - I am planning to use the Raspi as home AV, using the GPIO to turn on the amplifier and overhead projector, for example ;)

nullstring
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Re: Standardized Expansion Header

Thu Dec 08, 2011 7:27 pm

As I understand, it was done because these pins are not safe to use unless you know what you're doing.
They do not have high voltage tolerances, and they did not want people to accidentally hook them up to 5v sources and kill the chip.

In order to prevent this, they would have to add buffers to the ports, which would've risen costs.

I have no issue with their decision.
In fact, I would've welcomed a version in which none of the through-hole parts were soldered.

larsth
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Re: Standardized Expansion Header

Fri Dec 09, 2011 3:08 am

An external USB device could be useful. It should have voltage protection circuits and bi-drectional level shifters (howto hint: http://ics.nxp.com/support/doc.....n97055.pdf ).

If the USB device is using an inexpensive microcontroller with USB it should be easy to have a lot of fun with it.

That device would need a device driver to control the configuration of the board and to make data transfers + a program wich reads a configuration file an then does a setup of the board + a GUI program and/or shell script to create those configuration files.

It could be nice if The Raspberry Pi Foundation could get a USB Vendor ID, so us spare-time hardware develepers could get assigned a USB Device Id from the Raspberry Pi Foundation for free for a USB device wich can be used together with a Raspberry Pi.

hstubbs3
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Re: Standardized Expansion Header

Sun Dec 11, 2011 8:48 am

Quote from larsth on December 9, 2011, 03:08
An external USB device could be useful. It should have voltage protection circuits and bi-drectional level shifters (howto hint: http://ics.nxp.com/support/doc.....n97055.pdf ).

If the USB device is using an inexpensive microcontroller with USB it should be easy to have a lot of fun with it.

That device would need a device driver to control the configuration of the board and to make data transfers + a program wich reads a configuration file an then does a setup of the board + a GUI program and/or shell script to create those configuration files.

It could be nice if The Raspberry Pi Foundation could get a USB Vendor ID, so us spare-time hardware develepers could get assigned a USB Device Id from the Raspberry Pi Foundation for free for a USB device wich can be used together with a Raspberry Pi.

Sorta like an Arduino ?

larsth
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Re: Standardized Expansion Header

Sun Dec 11, 2011 3:09 pm

Quote from hstubbs3 on December 11, 2011, 08:48
Quote from larsth on December 9, 2011, 03:08
An external USB device could be useful. It should have voltage protection circuits and bi-drectional level shifters (howto hint: http://ics.nxp.com/support/doc.....n97055.pdf ).

If the USB device is using an inexpensive microcontroller with USB it should be easy to have a lot of fun with it.

That device would need a device driver to control the configuration of the board and to make data transfers + a program wich reads a configuration file an then does a setup of the board + a GUI program and/or shell script to create those configuration files.

It could be nice if The Raspberry Pi Foundation could get a USB Vendor ID, so us spare-time hardware develepers could get assigned a USB Device Id from the Raspberry Pi Foundation for free for a USB device wich can be used together with a Raspberry Pi.

Sorta like an Arduino ?

Yes and No.

No, if you decide that the device cannot be flashed with software/firmware, and yes if you choose a Arduino like device (I prefer a inexpensive ARM microcontroller).

Th microcontroller could be a STMicroelectronics STM32F103ZET6:
http://octopart.com/stm32f103z.....cs-7878626
wich has 1/2 MB flash, and 64 KB SRAM, and can access external memory with 4 banks of 16 MB RAM/Flash/ROM.
You could put a specialized Python interpreter on the flash

Note: English isn't my native language, so expect errors.

rmm200
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Re: Standardized Expansion Header

Fri Mar 23, 2012 12:43 am

I think I am on the mod's blacklist. I have a feature request not covered elsewhere, and my topic gets locked. So let me add it to this as-yet unlocked one:

In some future release, it would be extremely useful to use headers like the Arduino.

Enough lines broken out on both sides of the board to support a daughter board(s).

Easy expansion sure would make life easier for us experimenters.

It would require a slightly larger circuit board with signal lands along the perimeter. Connectors optional – soldering these in would be easier than lands scattered across the board.


Lynbarn
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Re: Standardized Expansion Header

Fri Mar 23, 2012 1:38 am

No, it's okay, you're not on a blacklist! - as I explained before, your thread was locked to avoid duplicating a discussion that has been covered several times before, as you have now found! There are actually that are more recent and go a lot further than this one.

Incidently, There ARE headers included on the Pi, for GPIO, DSI and DCI, and at the moment, it seems they are all populated, although that wasn't, I believe, the original intention. They may not cover all the ev\entualities you are seeking, but they do allow a wide range of applications and add-ons to be applied.

rmm200
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Re: Standardized Expansion Header

Fri Mar 23, 2012 2:15 am

Lynbarn said:

...
Incidently, There ARE headers included on the Pi, for GPIO, DSI and DCI, and at the moment, it seems they are all populated, although that wasn't, I believe, the original intention. They may not cover all the ev\entualities you are seeking, but they do allow a wide range of applications and add-ons to be applied.

I feel that I am not actually presenting my request well.  I am not asking for specific data lines to be broken out; I am asking for headers carrying power and data along the perimeter that would physically support a daughter board. The Arduino does this very well...  This is the part I thought was not a duplicate.

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tzj
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Re: Standardized Expansion Header

Fri Mar 23, 2012 2:21 am

probably won"t fit in here but what about a modular pi? to make a full use of the SoC as possable, and to make it header related, the headers would more or less be like the arduino if it ever came into being. this would be of coarse be for the advanced student.
http://www.themagpi.com <---- Checkout the MagPi
(The MagPi - Co-Founder)

mole125
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Re: Standardized Expansion Header

Fri Mar 23, 2012 12:08 pm

rmm200 said:


Lynbarn said:


...



Incidently, There ARE headers included on the Pi, for GPIO, DSI and DCI, and at the moment, it seems they are all populated, although that wasn't, I believe, the original intention. They may not cover all the ev\entualities you are seeking, but they do allow a wide range of applications and add-ons to be applied.


I feel that I am not actually presenting my request well.  I am not asking for specific data lines to be broken out; I am asking for headers carrying power and data along the perimeter that would physically support a daughter board. The Arduino does this very well...  This is the part I thought was not a duplicate.


I don't understand what you are asking for. The GPIO headers carry power and data and are sat at the edge of the board. onto this connector a daughter board can be mounted. What beyond this is it that you are actually requesting?

rmm200
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Re: Standardized Expansion Header

Fri Mar 23, 2012 2:31 pm

mole125 said:

...
I don't understand what you are asking for. The GPIO headers carry power and data and are sat at the edge of the board. onto this connector a daughter board can be mounted. What beyond this is it that you are actually requesting?
Chalk it up to a bad mental image on my part. I thought even the Gert board would be using some discrete wires to connect to the Pi. I will say an opposing connector (opposite edge) would provide rigidity and keep the daughter board from shorting.

mole125
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Re: Standardized Expansion Header

Fri Mar 23, 2012 2:57 pm

rmm200 said:


mole125 said:


...



I don't understand what you are asking for. The GPIO headers carry power and data and are sat at the edge of the board. onto this connector a daughter board can be mounted. What beyond this is it that you are actually requesting?


Chalk it up to a bad mental image on my part. I thought even the Gert board would be using some discrete wires to connect to the Pi. I will say an opposing connector (opposite edge) would provide rigidity and keep the daughter board from shorting.


There may be a benefit but I'm not even sure that will be required (depending on casing).

The thing I'm really really struggling is imagining the size that the board actually is. If you take a credit card out of your wallet and look at it it makes you realize how small the thing is.

For the opposite edge to bend down enough to short on the actual board would be a rather tight angle, besides which there are the ethernet and usb ports at the opposite corner for it to rest on (perhaps with a bit of insulating tape to prevent shorting to ground.

To be honest many home made daughter boards are likely to end up larger than the RPi if through hole components are being used and it'll be a case of how to support the RPi not the other way around.

rmm200
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Re: Standardized Expansion Header

Fri Mar 23, 2012 3:16 pm

mole125 said:

...
To be honest many home made daughter boards are likely to end up larger than the RPi if through hole components are being used and it'll be a case of how to support the RPi not the other way around. 

One last post on this.  One thing I really do not want to do is make my own expansion board. I am looking forward to the foundation or third parties making a good expansion board that plugs on the header. Couple of rails, room for several ics. Maybe even one that takes a (tiny) breadboard.

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Gert van Loo
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Re: Standardized Expansion Header

Fri Mar 23, 2012 3:29 pm


I thought even the Gert board would be using some discrete wires to connect to the Pi.


The first Gert board had a male header with very long pins soldered on it. The Pi was supposed to plug on top of that using a femal connector. Then the first beta boards came back and had a male header in place. So I had to use a short flat cable to connect them up.

I found it was much easier for debugging the prototype so on gertboard rev-2 I used the same system.

In the final product I leave it up to the user to do the same or put a female header on the gertboard and connect the two direct.

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