Integrating Teensy - questions about PCB fab and open source

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AidanRTaylor

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Hello, my name is Aidan, I'm a research assistant on the LAUGH project: https://www.laughproject.info/

In a nutshell, LAUGH is a social design project seeking to improve the lives of people living with late dementia. I do a lot of the hands-on prototyping as part of my role. I have made quite extensive use of Teensy along with the Prop and Audio shields as part of my prototyping.

I want to be able to streamline prototyping without having hours of wiring on my hands, I would like to make a PCB which would effectively be the Teensy 3.2, SGTL5000 and SD card reader along with some GPIO in a more compact and preferably populated format, but I have never done any more than double-sided unpopulated boards.

I have two questions, first - is Teensy open source hardware/firmware? Can I make a new board using the Cortex-M4 MCU and flash the Teensy firmware onto it? (looking for both legality and feasibility answers here) Is there some base firmware on a Teensy (other than blink) that allows you to flash it with the TeensyLoader?.

Second question is - when you want to order populated boards, how do you do it? How do you get parts to fabrication? How much more does it cost? (looking at probably under 50 boards)

I know that's a few questions sorry! I believe it's for a good cause though - I would really appreciate any insight from your own experience if you are willing to share it.
 
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Although this has been answered multiple times on these forums: The Teensy core files and the Teensy libraries are under the open MIT license. The hardware (see schematics page on the PJRC website) is also available for everybody.

Had you studied the schematics and all other reference stuff, you'd found that there is no boot loader code in the Teensy 3.x CPUs. The boot and code upload process is handled by a small coprocessor which contains the magic Teensy sauce and which you'll have to buy pre-programmed from PJRC. That's how their business model works. But that's the only "licensed" component, the other hardware stuff, even the main CPU might be legally bought on the "free market".
 
Would be interesting to see a summary of what the combined parts will be doing and how they'll be used?

depending on end use ... wondering if a T_3.5 with included SD adapter could work with just using the DAC's for sound of adding one of the PT8211 for amplification. Not an all in one solution - but simpler, cheaper - but more inbuilt capability with T_3.5 ( RAM, FLASH, pinned GPIO, 2nd DAC ) depending on what is needed. A simpler shield could be built to connect the T_3.5 without designing an MCU board.
 
Would be interesting to see a summary of what the combined parts will be doing and how they'll be used?

Hello defragster, so one example is our project "Hug" which is a soft doll-like object. Hug has a heartbeat and plays music. I used Teensy 3.2, the Teensy Audio Adaptor Shield, a seperate amp module, a lipo module and a simple phone vibration motor for the heartbeat which I made up a little PCB for. I use a very similar combination of modules in some of the other prototypes we have developed as it leaves enough GPIO to do a couple of nice things, the exceptions being a couple of devices that benefit from the accelerometer in the Prop Shield. Oh yes, and I have used the WS2812 chips on a couple of things. It ends up a fairly expensive combination of modules, but the bigger issue is time - making Hug electronics takes me at least an afternoon to solder up on veroboard and that's a simpler build.

depending on end use ... wondering if a T_3.5 with included SD adapter could work with just using the DAC's for sound of adding one of the PT8211 for amplification. Not an all in one solution - but simpler, cheaper - but more inbuilt capability with T_3.5 ( RAM, FLASH, pinned GPIO, 2nd DAC ) depending on what is needed. A simpler shield could be built to connect the T_3.5 without designing an MCU board.

Wow I hadn't paid enough attention to the PT8211, it's very cheap, thanks for this!

I was thinking about something like that, a PCB to slot a Teensy onto. I have a couple of Teensy 3.6 here but I haven't had a reasonable amount of time to play with them - I think the last time I did was last Summer when I did some experiments with the DAC! SD Card slots are also very cheap, I haven't looked at the Audio Adaptor for a while but I think there is very little in between the SD card and the GPIO pins it connects to.

Thanks for your reply!
 
Interesting project. Paul put the PT8211 for sale and FrankB made use of it and it ended up as a supported device in the AUDIO LIB.

Having the SD on the T_3.5 would save needing to make the SPI connections - so fewer wires/less soldering (times two w/SD adapter) to put to the Veroboard right there - also faster and more stable connection. And the spare 200 KB RAM and 256 KB Flash can't hurt for alternate/expanded effects and variability as desired.

Maybe a tilt switch or two could stand in for motion detection to reduce cost. T_3.5 won't be as battery friendly at higher speed - though recent posts showed starting it at 24 MHZ and shifting to 48 MHz if that would add enough speed - might make the battery last longer? And there is the WFI instruction that sleeps between interrupts - or the snooze library.

Seeing more of the project would be nice if you could share - even by PM - I scanned the LAUGH site and didn't pick up anything about this posted. - I'm interested because my 89 yo Mom is going further into dementia - would be nice to send her something to talk about 2,500 miles away. And final thought - the T_3.5 brings a RTC since you have a battery already - it could be time aware for daily events - or logging usage if that would help find the useful features/changes.
 
Second question is - when you want to order populated boards, how do you do it? How do you get parts to fabrication? How much more does it cost? (looking at probably under 50 boards)

Such low quantities are tough when using surface mount parts. The reality is pretty much everything about the conventional process is optimized for higher quantities, where setup costs are amortized over the many thousands of boards you'd normally make.
 
Thanks for weighing in Paul, I think defragsters suggestions were on point, but it was good to learn about the MkL02/4 for future reference. I hope one day that we can make 1000's of Hugs for people!

defragster -

I use tilt switches in Hug and some other objects - In Hug they work great but they can be very fiddly in some cases, I've found having a pair with one oriented 90º away from the other is ok, and better if you know which way an object is going to be generally oriented. Also the Prop Shield only has a tiny amount of flash memory so afaik it's only really ok for sound effects - but I guess you already know all that!

I will try and do some battery tests with the 3.5 soon - it may well be fine as I have found that most of our prototypes charge fast and last for hours anyway. Just need to find some time to experiment as always!

There is a recent video on this post, I am the shifty guy talking at the start - it's a bit promo-speak but hopefully digestable: https://www.laughproject.info/home-2/open-doors/

And this article was quite recent and describes the project quite well: https://researchfeatures.com/2018/01/31/laugh-improves-wellbeing-happiness-advanced-dementia/

Feel free to send me a message as well if you want to chat at all - it's late here, I have to get some sleep now. Thanks guys you have given me some good food for thought, I will share my next steps for the next noobie who can't use the search function ;)
 
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