User avatar
bonzadog
Posts: 258
Joined: Wed Apr 25, 2012 9:40 am
Location: Rietberg/Germany

Suggestion on HAT design

Sat Jan 13, 2018 9:50 am

13.1.2018

I have used HATS in my Pi's and some HATS do not have a 40 Header on the top.
This is annoying when one wants to use a HAT AND some GPIO pins and it forces one to solder wires on the required
GPIO pins. If every HAT passed the GPIO contacts to a header on top of the HAT this would be a huge help.

So my suggestion is to require a 40 Pin Header on top of very HAT.

BD

User avatar
davidcoton
Posts: 5041
Joined: Mon Sep 01, 2014 2:37 pm
Location: Cambridge, UK
Contact: Website

Re: Suggestion on HAT design

Sat Jan 13, 2018 10:49 am

Problem is, if that were part of the HAT spec, people would expect HATs to be stackable. In fact, boards built to the HAT spec are specifically NOT stackable (because of the EEPROM interface).
I have an Adafruit TFT board with a pass-through connector, which works for me. This particular board does not conform to the HAT standard so the only problem is making sure that the pins used are compatible.
And in any case, RPF has no control over the dozens of add-on designers, apart from those who want to claim HAT standard conformity.
Signature retired

User avatar
bensimmo
Posts: 4633
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Suggestion on HAT design

Sat Jan 13, 2018 10:52 am

They should all use the SenseHAT removable pin riser setup doobery. That would make it user choice.
Although the ones I used actually come with solder your own connector on. (Pimoroni iirc)

User avatar
bonzadog
Posts: 258
Joined: Wed Apr 25, 2012 9:40 am
Location: Rietberg/Germany

Re: Suggestion on HAT design

Sat Jan 13, 2018 6:48 pm

bensimmo wrote:
Sat Jan 13, 2018 10:52 am
They should all use the SenseHAT removable pin riser setup doobery. That would make it user choice.
Although the ones I used actually come with solder your own connector on. (Pimoroni iirc)
Hi,

Please explain removable pin riser setup doobery. Many thanks

User avatar
bensimmo
Posts: 4633
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Suggestion on HAT design

Sat Jan 13, 2018 10:37 pm

On the SenseHat the riser doobery can be pulled out and you can put a longer one in it or anything with pins into it.
it has some metal friction fit tabs that keep it all tight and in place.
No idea what they call it so try some picture searches.

User avatar
bonzadog
Posts: 258
Joined: Wed Apr 25, 2012 9:40 am
Location: Rietberg/Germany

Re: Suggestion on HAT design

Sun Jan 14, 2018 1:01 pm

davidcoton wrote:
Sat Jan 13, 2018 10:49 am
Problem is, if that were part of the HAT spec, people would expect HATs to be stackable. In fact, boards built to the HAT spec are specifically NOT stackable (because of the EEPROM interface).
I have an Adafruit TFT board with a pass-through connector, which works for me. This particular board does not conform to the HAT standard so the only problem is making sure that the pins used are compatible.
And in any case, RPF has no control over the dozens of add-on designers, apart from those who want to claim HAT standard conformity.
Then perhaps a consideration of a design for stackable HATS.

User avatar
mahjongg
Forum Moderator
Forum Moderator
Posts: 13105
Joined: Sun Mar 11, 2012 12:19 am
Location: South Holland, The Netherlands

Re: Suggestion on HAT design

Sun Jan 14, 2018 6:16 pm

bonzadog wrote:
Sun Jan 14, 2018 1:01 pm
davidcoton wrote:
Sat Jan 13, 2018 10:49 am
Problem is, if that were part of the HAT spec, people would expect HATs to be stackable. In fact, boards built to the HAT spec are specifically NOT stackable (because of the EEPROM interface).
I have an Adafruit TFT board with a pass-through connector, which works for me. This particular board does not conform to the HAT standard so the only problem is making sure that the pins used are compatible.
And in any case, RPF has no control over the dozens of add-on designers, apart from those who want to claim HAT standard conformity.
Then perhaps a consideration of a design for stackable HATS.
Stackability cannot be obtained simply, because random GPIO's used on each boards can and will conflict with each other, as only the I2C pins support a bus structure. adding logic to each HAT to solved conflicts is possible, but would make such boards very expensive, the boards then also need a mechanism to know at which "stack level" they are so the conflict resolving electronics can work, and there can be more than one EEPROM on the I2C bus, (each with an unique address) that would make these "TOP-HAT" boards even more expensive. Therefore the people of the RPF have wisely decided that HATs cannot be stackable. So yes, it was considered, and the decision was that it wasn't worth the effort and cost to try to pull this off. That said, there is nothing to stop a user to try to connect more than one HAT to a PI as long as he wants to forego the HAT EEPROM mechanism, and he resolves any occurring conflicts himself.
One way to physically do it would be to use a 40-pole IDE cable with multiple connectors to an expansion board.
there have been attempts to design a stackable set of boards, using a bus oriented interface (I2C).

User avatar
bonzadog
Posts: 258
Joined: Wed Apr 25, 2012 9:40 am
Location: Rietberg/Germany

Re: Suggestion on HAT design

Fri Mar 09, 2018 9:46 am

9.3.2018
Sorry for my late reply, some health issue got in the way.

So this situation is, if one uses a HAT and wishes to access unused GPIO pins then one is forced to
use a GPIO expander - there was a PCB sold that had three parallel GPIO 40 Pin Headers
but after some inquiry, I have found they are no longer being sold.
So I will need to build some sort of board that will do the same - otherwise
HATS that use perhaps 1 GPIO as IO and 4 for SPI or I2C and all the others pins would be wasted.
Still, if the current design stays then this is the only method available.

Off topic, on the next Pi, I would like to have more memory 2GB? and a onboard switch for a controlled shutdown.
But I can live quite well with the status quo.

The Pi has moved from an educational entity and is now well into the maker/hobbyist/industrial scene.

fruitoftheloom
Posts: 23387
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: Suggestion on HAT design

Fri Mar 09, 2018 9:58 am

bonzadog wrote:
Fri Mar 09, 2018 9:46 am
.

Off topic, on the next Pi, I would like to have more memory 2GB? and a onboard switch for a controlled shutdown.
But I can live quite well with the status quo.

The Pi has moved from an educational entity and is now well into the maker/hobbyist/industrial scene.

Yes totally irrelevant and the RPT/RPF are well aware of limitations, to suggest otherwise is derogatory.....sigh !!!
Rather than negativity think outside the box !
RPi 4B 4GB (SSD Boot)..
Asus ChromeBox 3 Celeron is my other computer...

willieaames
Posts: 18
Joined: Tue Aug 09, 2016 6:14 am

Re: Suggestion on HAT design

Fri Mar 09, 2018 10:24 am

Wouldn't this pull too much voltage?

User avatar
bonzadog
Posts: 258
Joined: Wed Apr 25, 2012 9:40 am
Location: Rietberg/Germany

Re: Suggestion on HAT design

Fri Mar 09, 2018 2:25 pm

fruitoftheloom wrote:
Fri Mar 09, 2018 9:58 am
bonzadog wrote:
Fri Mar 09, 2018 9:46 am
.

Off topic, on the next Pi, I would like to have more memory 2GB? and a onboard switch for a controlled shutdown.
But I can live quite well with the status quo.

The Pi has moved from an educational entity and is now well into the maker/hobbyist/industrial scene.

Yes totally irrelevant and the RPT/RPF are well aware of limitations, to suggest otherwise is derogatory.....sigh !!!
I am unsure what is being implied...The irrelevant bit ..OK One understood that and is true since was off topic but I was most certainly not being ,or intended , to be derogatory.

W. H. Heydt
Posts: 12671
Joined: Fri Mar 09, 2012 7:36 pm
Location: Vallejo, CA (US)

Re: Suggestion on HAT design

Fri Mar 09, 2018 3:33 pm

bonzadog wrote:
Fri Mar 09, 2018 9:46 am
Off topic, on the next Pi, I would like to have more memory 2GB? and a onboard switch for a controlled shutdown.
But I can live quite well with the status quo.
More RAM will require an entirely new SoC design. The GPU on the Pi has the memory controller and it is limited to 1GB. This is not to say that it won't ever happen, just to say that it won't happen to the Pi2B or Pi3B. This point also ignores whether or not it can be done and still keep the retail price at $35. Perhaps you'd care to donate $5 million to $10 million to the RPT to have a new SoC designed.

As for a physical power switch... There are a variety of ways to "roll your own". They generally take additional hardware, though. Bear in mind that abruptly dropping power risk SD card corruption, so an easy to use power switch is a risk. That said, the WD SATA adapter has a power switch built onto it, so if you're will to change to using a CM/CM3/CM3L you can have one.

User avatar
bensimmo
Posts: 4633
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Suggestion on HAT design

Fri Mar 09, 2018 3:35 pm

Do you mean the phatstack
https://shop.pimoroni.com/products/phat-stack?

Though it would be nice if you could rewire along the route.
E.g. if two hats used the same gpio, but didn't actually need to have that one, you could rewire the route from say bcm4 to bcm14 and then just alter the code.
But lots of wires, extra cost..

User avatar
karrika
Posts: 1124
Joined: Mon Oct 19, 2015 6:21 am
Location: Finland

Re: Suggestion on HAT design

Fri Mar 09, 2018 3:57 pm

bensimmo wrote:
Fri Mar 09, 2018 3:35 pm
Do you mean the phatstack
https://shop.pimoroni.com/products/phat-stack?

Though it would be nice if you could rewire along the route.
E.g. if two hats used the same gpio, but didn't actually need to have that one, you could rewire the route from say bcm4 to bcm14 and then just alter the code.
But lots of wires, extra cost..
It started with the 5" touch display that took all pins. So I soldered a socket to a PiZero so I could stack it on the PHATstack. The other cards are AudioInjector PiZero stacked with DMX controller DiscoCap.

It works... But did I get carried away with the PHAT stack?

Image

User avatar
bensimmo
Posts: 4633
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Suggestion on HAT design

Fri Mar 09, 2018 4:17 pm

Connect another PiZero via USB and use the gpiozero/gpio extender and another phatstack and then you'll be getting somewhere into hat overload..

Return to “Beginners”