mercury0x0d
Member
I've also been kicking around the idea of making some sort of "Teensy Pro" board which would bring out most (all?) pins for use. The target for this would be folks designing consumer-facing products which would look a little "cheap" if an end user were to pop the proverbial hood only to find their product was simply designed around an off-the-shelf microcontroller. No offense to the PJRC crew, of course, but in my mind, the Teensy is great for prototyping, but a final product needs something with a bit of a more purpose-specific appearance. And I don't think that's a controversial statement - after all, the bootloader chip is sold separately for a reason! 
For this design, I was at first thinking about doing a square-ish board with a row of pins on each side, but that was quickly shot down when I realized exactly how many pins still needed to be brought out. 128+ pins at the standard 2.54mm pitch would make for a ~3+ inches on all four sides. Way too large! Of course, you could reduce the pitch, but I think I have a better way.
I looked into a ton of options for connectors, but I think the best happens to also be the cheapest and simplest - good old pin headers. I'm currently envisioning something along the shape of the Motorola 68000 which, for those who never saw one, is a DIP-packaged CPU about 25% longer than a Teensy 4.1, at least from me eyeballing it. This would give 32-pin rows, which aren't too difficult to remove (I've done it) and would be even easier to remove when using low-profile pin headers or ZIF sockets. As I'm sure you already noticed, though, two rows of 32 pins only total 64. Where do those other 64 pins connect? To neighboring rows on the same sides - basically double rows of through-holes on each side. Such an arrangement was also brought up on the "future Teensy" thread, and possible configurations include:
Soldering all four rows - two per side - directly to a finished PCB:
All ~128 pins would be easily accessible this way, maximizing the I/O abilities of the iMXRT.
Soldering a single row of male pins on each side:
This configuration gives the breadboarder many more pins than a stock Teensy 4.1, with the flexibility to later have additional I/O available as well if it eventually gets soldered into a finalized PCB.
Soldering both male and female headers:
One row of male and one row of female headers soldered side-by-side, on each side, allowing all pins to be used even when breadboarding; 32 pins through the breadboard's connections and the remaining 32 via wires plugged into the female headers.
I'm not saying anyone has to adopt my ideas on this, but I figured I'd just throw it out there in case anyone finds it helpful.
For this design, I was at first thinking about doing a square-ish board with a row of pins on each side, but that was quickly shot down when I realized exactly how many pins still needed to be brought out. 128+ pins at the standard 2.54mm pitch would make for a ~3+ inches on all four sides. Way too large! Of course, you could reduce the pitch, but I think I have a better way.
I looked into a ton of options for connectors, but I think the best happens to also be the cheapest and simplest - good old pin headers. I'm currently envisioning something along the shape of the Motorola 68000 which, for those who never saw one, is a DIP-packaged CPU about 25% longer than a Teensy 4.1, at least from me eyeballing it. This would give 32-pin rows, which aren't too difficult to remove (I've done it) and would be even easier to remove when using low-profile pin headers or ZIF sockets. As I'm sure you already noticed, though, two rows of 32 pins only total 64. Where do those other 64 pins connect? To neighboring rows on the same sides - basically double rows of through-holes on each side. Such an arrangement was also brought up on the "future Teensy" thread, and possible configurations include:
Soldering all four rows - two per side - directly to a finished PCB:
All ~128 pins would be easily accessible this way, maximizing the I/O abilities of the iMXRT.
Soldering a single row of male pins on each side:
This configuration gives the breadboarder many more pins than a stock Teensy 4.1, with the flexibility to later have additional I/O available as well if it eventually gets soldered into a finalized PCB.
Soldering both male and female headers:
One row of male and one row of female headers soldered side-by-side, on each side, allowing all pins to be used even when breadboarding; 32 pins through the breadboard's connections and the remaining 32 via wires plugged into the female headers.
I'm not saying anyone has to adopt my ideas on this, but I figured I'd just throw it out there in case anyone finds it helpful.
