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Thread: Suggest next Teensy with Cortex M7

  1. #76
    Senior Member PaulStoffregen's Avatar
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    Many questions. Here's some quick answers...

    Only NXP can say for sure about their memory design choices, but it's easy to imagine the likely answer: cost.

    I need to be careful about the NDA, so I'm not going to comment about questions involving the chip's details or anything I might know about their plans for future chips in this product line.

    External SDRAM is one of the very difficult choices for a new Teensy. The situation is similar to Teensy 3.6, where FlexBus consumes many of the I/O pins and makes several important features unavailable. So I'm leaning against SDRAM (or keeping those pins unused). It simply costs too much, in terms of lost functionality.

    My hope is to move towards integrating conditionally compiled semaphone or mutux support into the core library and many of the most commonly used Arduino libs. I do not intend to make any RTOS mandatory, but quite a lot could be done in the many libraries so they work much better when used with an RTOS. This is the sort of thing best discussed on its own thread. But I will say right now, the 2 limiting factors are dev time to do this, and having RTOS users willing to help test unstable/alpha/beta code. Both of these always seem so elusive...

    Release of bootloader chips and a reference board will almost certainly look similar to prior times. Never before have I managed to get these done right at the Teensy board's release. There's always a ton of stuff to do leading up to the release, and then usually a few months of highly urgent software work following. I'm pretty sure a first Cortex M7 board will be similar.

  2. #77
    hm.. ok, so i basically need to stick with my teensy 3.2 until the core libs get rtos support (luckily i can wait)
    too bad i can't help you with testing (and indeed, this is a bit offtopic)

    regarding the sdram: will there be a possibility of a teensy version with it and one without? (like you did with the usb host on t3.5/t3.6)

    tbh, i'm looking forward to what the future brings with the teensy 4.0!

  3. #78
    Interesting the T_3.6 has been out a year now and RTOS hasn't been ported to it? It would be a big step up from the T_3.2 RAM and Speed wise - plus flash and extended hardware. The multitasking support used is part of the processor design - and the T_3.5 and 3.6 seem to have that functionality as least as good - there are one or two other real time switchers in progress on the forum that seem efficient and effective.

    The " (like you did with the usb host on t3.5/t3.6) " was a natural fallout of making a new Teensy that was still 5V tolerant ( the T_3.5 ) and the enhanced T_3.6 that is not 5V tolerant but adds more features and capacity - one of which was the usb host support. The MCU's share the same package layout to the point the same PCB is used - where the T_3.6 can do usb host and the T_3.5 without that hardware exposes two added analog pins.

  4. #79
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    Been reading about level shifters. The new board will not be 5v tolerant we know that. But what level shifters can be used and for what pins. Are different ones more appropriate for I2C, SPI, digital pins etc? Bi-directional?

  5. #80
    Moderator MichaelMeissner's Avatar
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    Quote Originally Posted by mjs513 View Post
    Been reading about level shifters. The new board will not be 5v tolerant we know that. But what level shifters can be used and for what pins. Are different ones more appropriate for I2C, SPI, digital pins etc? Bi-directional?
    Note, I'm a software guy, but I have to imagine the same issues will hold for the new chip as well as the current LC/3.6 chips. Given that the new board will still be 3.3v, any solution you use now should work with the new board. In general, it is better if the communication is unidirectional (i.e. a pin is an output pin or an input pin and never both). If you have to use bidirectional level shifting (i.e. i2c, spi), it can slow things down, and there are various caveats about its use cases.

  6. #81
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    mjs513, im prepping the 3.5 to be slave ready when the 4.0 comes out, keep posted in my other thread

    level shifters not needed

  7. #82
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    @tonto81. Which one

  8. #83
    Senior Member PaulStoffregen's Avatar
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    Probably this thread.

  9. #84
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    @PaulStoffregen. Sorry for the delay in responding, had major problem with computer. Thanks, will go through it. Think this is related to a couple of other threads as well now that I see the one that you referenced.

  10. #85
    Moderator Frank B's Avatar
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    NXP:
    "The first crossover processor, the i.MX RT1050, is sampling with limited availability. Broad availability targeted for October 2017."

    Any chance that I could get a sample and access to a datasheet ? Anyone know what I have to do ?

    Edit: I've found an application note (using L1 cache): https://www.nxp.com/docs/en/applicat...te/AN12042.pdf
    Are there more ?

    Mouser sells this board: http://www.mouser.de/new/nxp-semicon...imxrt1050-evk/
    If I knew how compatible it was with the teensy, I might buy that...
    Last edited by Frank B; 10-19-2017 at 08:44 PM.

  11. #86
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    That board is $83, and is still a Cortex-M.

    Compare to https://www.adafruit.com/product/3400 which is $10 and has built-in WiFi, Bluetooth, and HDMI... (and is much smaller.)

  12. #87
    Senior Member Epyon's Avatar
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    Quote Originally Posted by jwatte View Post
    That board is $83, and is still a Cortex-M.

    Compare to https://www.adafruit.com/product/3400 which is $10 and has built-in WiFi, Bluetooth, and HDMI... (and is much smaller.)
    But does the Pi Zero has deterministic low-level I/O usable without an OS and additional peripherals like external RAM? As far as I can see the i.MX RT is still a microcontroller while the RasPi is a microcomputer.

  13. #88
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    You don't need external RAM on the Pi, but you do need external flash. (some people think this is a benefit....)
    Technically, yes, you can run any code you want in kernel mode with perfectly predictable peripheral response times.
    There's even a kit to load your own code, no OS needed (the "alt OS-es" on the Pi use this.)
    I freely admit that doing so is a lot harder than the excellent support Paul has put into Teensyduino, though.

    I also agree that there are different needs for different use cases. This is why I use a Teensy 3.2 slaved to a Pi 3 and a Teensy 3.5 slaved to a Jetson TX2.
    But the Cortex-M7 is moving somewhat in the wrong direction. It reduces I/O flexibility (losing analogs, voltage tolerance, etc,) in order to move in a direction that the Pi already solves just fine.
    This new board has a camera input, and a display output, but doesn't have the image processing oomph to actually do what you'd want to do if your projects have real display and camera requirements.
    (The Pi W has the VideoCore.)

    Aaanyway. For as long as the 3.5 stays in production, I'll be a happy Teensy customer.

  14. #89
    Senior Member PaulStoffregen's Avatar
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    One is a mature mass market product and the other is a first run eval board. Both are probably being sold at near cost. Notice the qty=1 limit and attempts to upsell related items on the Pi Zero.

    NXP's board is loaded with fairly expensive parts, and it's physically huge! I have one here on my desk. As far as I know, the schematic is still under NDA. But I believe it's probably pretty safe to comment that they spared no expense at filling the board up with lots of fancy features you don't get with Raspberry Pi's circuit board. It even has an overvoltage circuit featuring extra mosfets at its input. Honestly, I'm pretty amazed they're selling them so cheap.

    Obviously PJRC is not going to make a Teensy 4 board that retails near $80. It's far too early to finalize pricing, but I can tell you I am pretty focused on keeping the cost reasonable. I can also tell you there's no way a tiny, USA-based, independent company like PJRC can hit the $10 retail price of Raspberry Pi Zero.

  15. #90
    Moderator MichaelMeissner's Avatar
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    Quote Originally Posted by PaulStoffregen View Post
    Obviously PJRC is not going to make a Teensy 4 board that retails near $80. It's far too early to finalize pricing, but I can tell you I am pretty focused on keeping the cost reasonable. I can also tell you there's no way a tiny, USA-based, independent company like PJRC can hit the $10 retail price of Raspberry Pi Zero.
    Every so often, I track the pi-zero and pi-zero w. I will note, that a lot of times in the past, it has been impossible to get them. Adafruit seems to have them now, but limit you to 1 per customer. The brick & mortar store Microcenter seems to have them, but if you buy more than one, the price goes up (hmmm, the local Microcenter is currently having the Zero-W's on sale for $5, maybe they are getting rid of inventory). The big sellers like Element14/Digikey don't carry it, but they carry the bigger models.

    I suspect the Pi-zero exists to further the goals of the R-pi foundation (get computers to kids). It is probably break-even at best or maybe lose a little, and they run off a few runs of the Pi-zero in between Pi-3 builds. There isn't enough margin for distributors to sell it. Those that do, tend to either hope to make up the difference in add-on boards, or are focused on hackers themselves. Lady Ada has said as much in one of her web-casts, back when the supply was much tighter than it is now when answering a question of why they limited it to 1 per person. I recall when I used to follow the Adafruit forum more than I do now, that I was answering a question on the pi zero, and went to their page to look up something. At the time, there was like 30 available, and I quick did an order. Within an hour, they were sold out again.

  16. #91
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    Sure, although the Pi Zero would still be great value at $15 or $20.
    And I happily pay the $20 for the Teensy 3.2 and the $30 for the 3.5.
    But, I would rather keep doing that, than pay <whatever> for what I currently know about the "4."
    I've said it before, so I'll shut up now. I'll behave, I promise!

  17. #92
    Senior Member manitou's Avatar
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    Quote Originally Posted by Frank B View Post
    NXP:
    "The first crossover processor, the i.MX RT1050, is sampling with limited availability. Broad availability targeted for October 2017."

    Any chance that I could get a sample and access to a datasheet ? Anyone know what I have to do ?

    Edit: I've found an application note (using L1 cache): https://www.nxp.com/docs/en/applicat...te/AN12042.pdf
    Are there more ?

    Mouser sells this board: http://www.mouser.de/new/nxp-semicon...imxrt1050-evk/
    If I knew how compatible it was with the teensy, I might buy that...
    Digikey also sells the board ($84, quantity available: 0) https://www.digikey.com/product-deta...517-ND/7646293
    and presumably MBED will have software support "real soon". I did lots of experimenting with MBED K64 before the T3.5/3.6 beta release.

  18. #93
    Senior Member manitou's Avatar
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    Last edited by manitou; 10-27-2017 at 05:27 PM.

  19. #94
    Moderator Frank B's Avatar
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    Many features. We don't even have for important things of the T3.6 "official" libraries. Who's gonna write all this?

  20. #95
    Senior Member duff's Avatar
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    It looks like this chip has power on/off function builtin for an external button. Reading through the ref manual, the registers look much different from m0, m4 especially for low power. No LLWU and I still can't figure out how you set which sleep mode to go in though you still just call wifi to put the processor into sleep. From what i can tell so far the low power settings are much more involved in so much you have a lot more to do to get really low power modes.

  21. #96
    Senior Member manitou's Avatar
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    Quote Originally Posted by Frank B View Post
    Many features. We don't even have for important things of the T3.6 "official" libraries. Who's gonna write all this?
    We will need a flock of Pauls, me thinks.

    Quote Originally Posted by duff View Post
    It looks like this chip has power on/off function builtin for an external button. Reading through the ref manual, the registers look much different from m0, m4 especially for low power. No LLWU and I still can't figure out how you set which sleep mode to go in though you still just call wifi to put the processor into sleep. From what i can tell so far the low power settings are much more involved in so much you have a lot more to do to get really low power modes.
    There are a lot of differences from the T3* MCUs. In the application notes, there is a high-level Migration guide from Kinetis

  22. #97
    Moderator Frank B's Avatar
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    I wonder what happens with "double" - as TD handles such literals as "float" by default.
    Last edited by Frank B; 10-27-2017 at 09:51 PM.

  23. #98
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    Quote Originally Posted by Frank B View Post
    I wonder what happens with "double" - as TD handles such literals as "float" by default.
    Is that default behaviour not only for constants?
    We already know that any deviation from standard (here: defaulting float constants to 'float') will generate at some time diffusion, work-arounds and 'ugly' code

  24. #99
    Senior Member Blackaddr's Avatar
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    As for all this discussion against the Pi, the bottom line is if somebody out there had a Pi3 comparable processor with Arduino library support, I'd be all over it. But they don't. Many people have great ideas, but don't have the time/skill to successfully implement the libraries they need. Arduino popularity is driven by it's libraries. Pi popularity is driven by Linux (and hence access to Linux libraries and projects).

    The Audio library is a perfect example of this. You can be a very novice programmer and be up and doing your own basic audio manipulation very quickly.

    I think the success of the Teensy/Arduino is because it massively lowers the barriers to entry for many hobbyists, the breadboarding means they can implement it on real custom projects which is tough to do when someone has slapped connectors you don't need all over a huge board (e.g. conventional Arudino and Pi), and finally the processing power and memory available on the Teensy also far exceeds that of most other Arudino boards.

  25. #100
    Senior Member Epyon's Avatar
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    There are probably a dozen boards combining processor power such as found in the RPi3 (or even ten times more) with embedded Arduino with all the library support. UDOO being the most common I think (now also available in x86 flavour). The thing is that RPi and Arduino are apples and oranges. People buy RPi to be able to interface with a high level OS that obscures all the murky hardware details and in stead allows them to focus on stuff like GUIs or internet services, while Arduino makers are looking for that low level hardware access and eschew those fancy high level features.

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