Any Plans for a Teensy Board with Bottom Pads on Top?

[randomvibe]

So many useful bottom pads on my Teensy3.6. Any plans for a longer version so that all pads are on top? For the users it would be very accessible and still breadboard friendly. I suppose that's a huge redesign effort and structural problems may arise.

I'm not a fan of adapter boards - more cost and more time. As a Teensy user with very limited time, I just want to make projects.

[tonton81]

the answer is no, teensy 4.0 is being worked on for the future, i doubt time will be spent on redesigning current models unless you or others pay someone to make your own board and order the bootloader chips from pjrc

most people use 4 full row of headers at bottom

[KurtE]

depending on your needs, you could simply mount the board upside down to have the bottom pins available... Of course reaching the program button becomes a little more tricky

[randomvibe]

most people use 4 full row of headers at bottom

This defeats the purpose of quick prototyping on a breadboard.

...i doubt time will be spent on redesigning current models ...

I can appreciate that. But in the future, it would be nice to have either: (1) a longer Teensy board with all pins on top, or (2) a Teensy3.6-like configuration with a female micro-connector on top giving the user the option to expand with a ribbon cable like this: (as an example)

https://www.digikey.com/product-deta...032-ND/4844422

Just making suggestions as a Teensy customer.

[PaulStoffregen]

Are you really suggesting future Teensy should be designed for use with a $316 cable? That might be kinda outside of most people’s budgets?

[randomvibe]

Are you really suggesting future Teensy should be designed for use with a $316 cable?

No of course not. That's just an example, and a horrible one at that. Here's a better example:

https://www.adafruit.com/product/2098

The main point of the suggestion is this: bring out the bottom pads on top as an integrated connection port that can be accessed with a cheap cable like the one above. That would be far cleaner than current adapter boards and the Teensy would remain breadboard friendly.

[defragster]

No of course not. That's just an example, and a horrible one at that. Here's a better example:

https://www.adafruit.com/product/2098

The main point of the suggestion is this: bring out the bottom pads on top as an integrated connection port that can be accessed with a cheap cable like the one above. That would be far cleaner than current adapter boards and the Teensy would remain breadboard friendly.

Back before Paul showed the 'existing spec' napkin drawing - and before it was known to have a waste of space ... errr ... I mean really handy SD adapter over the otherwise wasted space on the extended PCB end, suggestions and input were provided regarding some hi density connectors. The Adafruit price on the connector is $1.95 that would need space and add cost to each board to add such a connector that may or may not provide a good solution even to the folks that needed more pins than exposed. PJRC was so cost conscious the T_3.5 and T_3.6 even share the same 4 layer PCB.

The pre-beta Proto board for the T_3.6 was really nice - a bit bigger than an UNO and all pins were present on a 2 layer board using a larger processor with legs that were hand soldered. An updated reference version of that PCB is available on OSH: 3"x2.5" Teensy 3.6 DIY Reference Board

[WMXZ]

An updated reference version of that PCB is available on OSH: 3"x2.5" Teensy 3.6 DIY Reference Board

But Paul still has to add the part numbers (as the TODO says)
Also a paste mask Gerber file would be useful to avoid hand soldering and allow reflow oven.

[PaulStoffregen]

But Paul still has to add the part numbers (as the TODO says)

I've "fixed" it be deleting that TODO.

Realistically, I'm not ever planning to do more on that OSH Park shared project page. The idea was merely to share the PCB, which had already been designed for the beta testing, with anyone who wanted to build it.

[PaulStoffregen]

Here's a better example:

https://www.adafruit.com/product/2098

How do you imagine that huge connector fitting on Teensy 3.6?

[randomvibe]

How do you imagine that huge connector fitting on Teensy 3.6?

Okay, I see I need to be more specific and practical with my suggestions.

Did some more digging and found a good example of a micro connector that would fit on top. This suggestion applies to future Teensy boards, not T3.5 or T3.6.

https://tinycircuits.com/collections...rocessor-board

It believe it enables 36 connections, and there are likely smaller ones with less pins.

If the cost is too high, it can always be an option for the customer.

Another suggestion would be: make the bottom pins available as headers as you already do with AREF, A10, A11, Reset, Program, etc.

Some of the reasons why I switched from Arduino Due to Teensy was less cost, more power, and breadboard friendliness. There was no going back from T3.2 to T3.6. But if those bottom pins could just be more readily available though.

[tonton81]

Are you really suggesting future Teensy should be designed for use with a $316 cable? That might be kinda outside of most people’s budgets?

people would pay that for a well supported product such as yours

[tonton81]

Some of the reasons why I switched from Arduino Due to Teensy was less cost, more power, and breadboard friendliness.

so why redesign it to be more expensive and end up making it look like O-HENRY bar for your breadboard?
people dont put “breadboards” in production products, breadboards are for testing, developing, nobody wants a O-HENRY sized mcu in their project

[tonton81]

you can get header extensions that will lift the pcb above board level and you can wire necessary pins on the center pads (which a header was soldered to). this is breadboard friendly, and doesnt involve wasting time and increasing product cost

[PaulStoffregen]

There are a lot of difficult trade-offs to make. Another consistent feedback is the 3.5 and 3.6 boards are physically too large for some projects. Sure, many people prototype on breadboards, but then they often put it all inside something else.

Cost is also a big issue, especially compared to ESP and Raspberry Pi. Aside from the cost of parts, keeping all the hardware the same is the biggest factor. Offering different options divides the manufacturing batch sizes, which drives up the costs, and it becomes much less realistic for distributors to carry. It’s easy to imagine adding more models from only a technical perspective, but that’s only half of the story. To make Teensy work long term, the business model has to be realistic, which is increasingly difficult in a market flooded with subsidized products (Pi Zero) and ESP modules, and of course Chinese clones.

But I am considering something like this, likely smaller, probably more focused on a specific purpose like an 8 bit TFT. There are still many choices to be made. Just please understand we’ve been down this discussion many times before. The combination of engineering trade offs and economic reality of a fully independent dev board (not financed by any big semiconductor company) means not everything that can be imagined actually is practical.

[randomvibe]

The combination of engineering trade offs and economic reality of a fully independent dev board (not financed by any big semiconductor company) means not everything that can be imagined actually is practical.

I appreciate that fully, and please take my suggestion as a suggestion only. Not having the bottom pads more readily available is not a deal breaker.

On the size of the T3.5 and T3.6, my feedback on that is a big thank-you-very-much for bringing out all those pins. For me, the size and form-factor is excellent. It is much smaller than the Arduino Due footprint I was dealing with.

[PaulStoffregen]

One of the other possible options for future boards would be new form factor Arduino is using, or Adafruit's very similar Feather format. They both seem really large though...

[randomvibe]

One of the other possible options for future boards would be new form factor Arduino is using, or Adafruit's very similar Feather format. They both seem really large though...

When I saw those awhile back, my first impression is that they were copying the success of the Teensy.

For me, the Feather is too small, just not enough pins on the sides. To my earlier alternate suggestion, I do like how the Feather makes a bunch of pins available on the top, like the Teensy3.6's AREF, A10, A11, Reset, Program, etc., but much more. I'd rather have a T3.6 with more side pins so I can prototype faster on a breadboard, and have top pins available for more elaborate projects.

Having those top pins does add the potential for add-ons like the TFT you were thinking about.

[defragster]

Of course as a 6 layer board - each through hole comes at a great cost. Paul was very happy he had routing room as it was.

<EDIT> 6 layer not 4 ....

[oric_dan]

the answer is no, teensy 4.0 is being worked on for the future,

Is there a link to this putative Teensy 4.0? I've done a google search but not quite found what looks to be such a thing.

I'm not suggesting Paul do this, but if I were adamant about bringing the bottom pins [currently smt pads] of 3.x boards out in a relatively painless manner, I would add a 2nd parallel row of through-hole pads along the upper edge of the boards. This would have very impact on overall board sizes, and might actually make routing a bit easier.

[PaulStoffregen]

@Defragster - The Teensy 3.5 & 3.6 PCB is actually 6 layers.

[WMXZ]

Is there a link to this putative Teensy 4.0? I've done a google search but not quite found what looks to be such a thing.

there is another thread where Paul indicated his plans to work on a T4.0
https://forum.pjrc.com/threads/44298...l=1#post147636


AND the other monster thread on T3++ (aka T3.5/6) https://forum.pjrc.com/threads/24633...ll=1#post38321 that lasted 3 years
This particular thread is of interest if you wanted to know Paul's reaction to all the suggestions on pins/form-factor etc. etc.

suggest to read the both threads from beginning to end

[PaulStoffregen]

I would add a 2nd parallel row of through-hole pads along the upper edge of the boards.

So far, every Teensy has been 0.7 inch (17.8 mm) wide. Wouldn't that mean growing the width to 0.8 inch (a 14% increase)?

[defragster]

@Defragster - The Teensy 3.5 & 3.6 PCB is actually 6 layers.

Yikes/opps - corrected above - that makes every big fat through hole take out even more real estate for vias and traces as well as disrupting the GND and power plans right?

[tonton81]

Nobody will want a klondike bar sized teensy over a single user's opinion. His concern is breadboard friendliness, whereas it doesnt matter in project use for 99% of others.