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I have a blinkt pHat that covers the entire GPIO pin array and I'm trying to trigger changes to the LED array after an external prompt. I expected to use a momentary switch connected to the GPIO pins, but the blinkt covers all of the GPIO pins ... is there another set of contacts I can solder some pins to and create an additional spot for a switch, or is there a way to stack headers in such a way that I can "tee" into two pins, or otherwise access two of the GPIO pins?

This is on a pi zero w if it matters.

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Question

How to access the GPIO pins blocked by a HAT?


Answer

Update 2019oct27hkt0936

Suggestion 10 - DIY or AliExpress/Amazon available stackable HAT

enter image description here

Update 2019oct23hkt0953

There are many ways to access the GPIO pins blocked by the HAT, each with pros and cons, as summarised below.

(1) Small foot print double breakout, space saving, but rather expensive (Suggestion 1, 3).

(2) Ribbon cable, easy to access GPIO pins, but needs more space (Suggestion 2).

(3) Replace the built in adapter from HAT by DIY one. Easy and flexible, but might have poor contact problem. (Suggestion 4)

(4) Extend the connecting pins between Rpi PCB and HAT, and use DIY 2 wire to one pin wire, or solder / AWG30 wire wrapping. This needs middle level DIY skills (wire wrapping is very reliable, but needs skills and professional tools) (Suggestions 5 to 9).


Suggestion 1

40 pin header breakout


Suggestion 2

ribbon cable


Suggestion 3

header breakout


Suggestion 4

header breakout


Suggestion 5

forked pin


Suggestion 6

header 6


Suggestion 7

stackble header


Suggestion 8

long pin


Suggestion 9

header 8

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References

(1) AliExpress Rpi GPIO stackable extra long 20 pin x 2 header - US$2

(2) AliExpress Ugeek Rpi 20x2 GPIO Header, stackable, double male, right angle male, female header - US$3

(3) AB Electronics Stackable Rpi HATs

/ to continue, ...


Appendices

Appendix A - What is the difference between "HAT", "pHAT", and "bonnet" ?

pHAT usually referred to "partial" HAT, a small size HAT for RpiZero/W. Lady Ada calls it a "bonnet".

/ to continue, ...


End of answer

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    Your pictures are ... interesting, but would be more useful with at least a short description. I've had difficulty finding the split/tappable headers as well, but I'm sure they exist. Thank you for the variety of ideas though, they have been a good starting point for further research. – user3.1415927 Oct 23 at 1:16
  • @user3.1415927, Your suggestion is good. So I have updated my answer with an introductory summary of the suggestions. Actually I have a couple more other suggestions, but some are HAT specific, ... In case you are particularly interested in any of the suggestions, I am happy to give more details. – tlfong01 Oct 23 at 1:58
  • @user3.141592, I have just updated my answer with yet one more suggestion: an example of a stackable HAT. By the way, I did not explicitly mention that Piromori is a good place to find maker friendly pins and headers etc. As you can see in my answer they have the most comprehensive collection of such things. However I hesitate to mention the name Piromori (or AdaFruit), because I am a poor hobbyist, and I NEVER buy expensive toys from AdaFruit, SparkFun, or Piromori. I do recommend them, but almost always at the same time I also show how to buy cheaper versions from AliExpress or TaoBao. – tlfong01 Oct 27 at 1:48

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