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Thread: The power of the Mini54 & alternative bootloader code?

  1. #1
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    The power of the Mini54 & alternative bootloader code?

    The Teensy that I've been using at work has been a major enabler for our project, which has led inevitably to the question of how we can apply its non-brickable feature to our application. We will be connecting multiple devices through RS-422 (or inexpensive plastic fiber*) connected serial ports rather than USB.

    Paul, Have you considered or would you consider the possibility of customer-provided bootloader code in place the existing USB bootloader?

    My co-workers and I are planning to use some EE tricks (essentially a slightly glorified RC network) to force assertion of the PROG signal upon detection of broken firmware. Given a bootloader that supports our protocol and connectivity requirements, we would have a totally unbrickable remote teensy. It is our intent to seal these devices into fully potted enclosures, so the Teensy's perfect record of recovery in the face of firmware bugs has great value to us.

    * Check Avago's plastic fiber for a really great way to implement signal isolation where point-to-point connection is a viable choice. I have no connection with them other than being happy that we can get great isolation inexpensively and with good bandwidth.

  2. #2
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    Check with Mark of uTasker. He's done secondary bootloader products for ARMs and maybe Teensy.
    One such thread
    https://forum.pjrc.com/threads/25323...t=utasker+boot

    the USB bootloader for Teensy 3 is a combination of control and code within the Mini54 microprocessor and interaction with the K20 ARM. Though I and others have inquired about remote reprogramming and related, Paul so far is hands-off on this. The uTasker mentioned above is the only thing I've read here on this topic.

    Avago's POF - interesting. 20m distance limited cheap plastic fiber. Good for certain industrial and flammable/explosive situations (class/div).

  3. #3
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    Good points. I've already alerted my manager of the uTasker work, and he has expressed interest in their projects and products. We'll probably move more decisively early in the new year. It's reasonable for Paul to preserve the value of the Mini54 work, it's a wonderful invention. I am hoping there's a way for Paul to preserve that value but with a serial twist. :-)

    My attraction to the Teensy is that it already exists as a hardware product whose form factor is nearly perfect for our upcoming prototyping project phase.

    On the topic of Avago plastic fiber: Our research and discussion with Avago reps has them talking about 50m limits; I would appreciate reading any commentary you may have or can direct me to that describes developers' real world experience. We really want to spec up to 30m reliably and are hoping for 40 for some of our customers. A typical installation has 1 to 4 runs of up to 30 meters (with the occasional demand for 40), connecting a fairly large number of devices with < 1 meter links. That first step is the challenge....

  4. #4
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    what data rates? If modest, a conventional (cheap) opto-isolator would do? Or is copper prohibited even with galvanic isolation?
    Better than simple low power RF data radios? (Which is my expertise/consulting work)

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