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Who's on first: feather e-paper & crickit/hallowing
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Who's on first: feather e-paper & crickit/hallowing

by michaelmeissner on Sun Mar 03, 2019 11:25 am

Most feathers and featherwings have the 16 and 12 pin connectors so that you can solder the pins so they are underneath the board or on top of the board (or both with stackable headers).

However a few only have the 16/12 pin connectors on one side (2.13" tri-color e-paper display, TFT FeatherWing - 2.4" 320x240 Touchscreen, Adafruit CRICKIT FeatherWing, and the HalloWing M0 Express). This means that you can only mount feathers/featherwings in one orientation.

I just got my 2.13" tri-color e-paper display, and I noticed that is no convenient way to mount a Crickit, feather board, and e-paper display, as the Crickit and the display have the pins in opposite orientation. In particular, you would want the Crickit on the bottom due to its size, the feather in the middle, and the display on top so you can see it. I could imagine the TFT display with its touch screen might also be rather useful with the Crickit.

I see the same with with the Hallowing and the Crickit. With the Hallowing, I imagine there isn't much call to use a e-paper display since it has its own TFT display, but it is a problem if somebody wanted to do it.

While you could use the Featherwing Doubler or Tripler and some creative soldering or just use a jumper wires, I wonder if there might be a market for a specialized Doubler or Tripler board where one of the connections is reversed, so you could mount the Crickit in the middle, and the feather and e-paper display on each the two ends.

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Re: Who's on first: feather e-paper & crickit/hallowing

by lisleman on Mon Mar 04, 2019 12:43 am

Interesting. Just wondering, I suspect if you stacked too many display type wings the power would become a problem.

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Re: Who's on first: feather e-paper & crickit/hallowing

by michaelmeissner on Mon Mar 04, 2019 1:56 am

Sure, there is always a limit of the amount of power used, and displays can eat a bit of power. But in the example I was talking about, there is only one display (and the crickit needs to be powered separately, so it doesn't count in terms of the total power).

I happen to have 2 versions of the Teensy uncanny eyes program (https://learn.adafruit.com/animated-ele ... 1/overview) running. One uses the Teensy 3.2 with 2 TFT displays (150x150 pixels). It generally consumes about 105mA (TFT monitors tend to have fairly consistent power draws because the big draw is the backlight to illuminate the pixels).

I also have a Teensy 3.5 running 2 OLED displays (also 150x150 pixels). Its power draw goes from about 125mA to 250mA. Note, I have the displays connected to the VIN pin, which has a roughly 500mA fuse between the USB power and VIN, but even so, I probably would hesitate to put another OLED display on the system.

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Re: Who's on first: feather e-paper & crickit/hallowing

by adafruit_support_carter on Mon Mar 04, 2019 11:11 pm

For the FeatherWings you mention, it's largely a design trade off. But also, they are all displays, so really only makes sense to have them on top.

In particular, you would want the Crickit on the bottom due to its size, the feather in the middle, and the display on top so you can see it.

This seems fine. Why is that arrangement an issue? You'd probably want to use these on the Feather main board:
https://www.adafruit.com/product/400

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Re: Who's on first: feather e-paper & crickit/hallowing

by michaelmeissner on Sun Mar 10, 2019 1:29 pm

I've been trying to figure out how to show what the issue is. It is easy to see if you just take the boards, and take some pins and try to stack them up.

The simplest way to show the issue is to take a feather crickit and a Hallowing. No matter how I turn the Hallowing, I cannot get the 12 and 16 bit pin headers on the Hallowing to line up with the appropriate segments in the crickit.

Similarly, if I have a M4 Express, It mounts fine on top of the crickit if you solder pins so the pins are underneath the board. The crickit however cannot be mounted if the pins are on top of the M4. Now, just for those two boards, you would probably never want to mount the crickit on top, just due the size issue.

And similarly, the two displays (e-paper, and TFT) would mount fine underneath the M4 Express, but will not mount on top of the M4 Express.

So if you wanted to use a M4 Express, crickit, and one of the larger feather displays, you can't put all of them together without either soldering up a protoboard that reverses the connection or using a collection of 12 pin and 16 pin dupont jumper wires to do the transformation.

The crickit and displays are wide enough that you could not put both the crickit and display on each side of a feather tripler board.

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Re: Who's on first: feather e-paper & crickit/hallowing

by adafruit_support_carter on Mon Mar 11, 2019 1:22 pm

Thanks. I see what you are talking about now. Yah, there are a few Wings like the Crickit and the TFTs that really can only go underneath the Feather, like this:
[top:feather:bottom] = [crickit / tft]
The more typical Wings can stack on top, like this:
[wing] = [wing] = [top:feather:bottom]
or by solder the headers different can also do this:
[top:feather:bottom] = [wing] = [wing]
The HalloWing, which is actually more like a Feather than a Wing, is like this:
[top:hallowing]
where there is no access to the "bottom".

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Re: Who's on first: feather e-paper & crickit/hallowing

by michaelmeissner on Wed Mar 27, 2019 11:40 am


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