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    Ditto Jonr's comment about C++. You can implement...

    Ditto Jonr's comment about C++. You can implement C code using a C++ compiler, but not the opposite. And I'm a big fan of Paul's comment about experimental learning. I think it's best to learn by...
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    We have the T4's smart peripherals to handle...

    We have the T4's smart peripherals to handle extremely low-level details. In my robotics-centric world I see the M4 as a highly programmable mid-level controller, well positioned to offload...
  3. I've plopped my current code to githib here...

    I've plopped my current code to githib here. You'll be interested in LedServices.h and LedServices.cpp

    My application requires constant frequency, with variations in the "High" times. It seems...
  4. I'm using the T4's FlexPwm to drive Neopixels....

    I'm using the T4's FlexPwm to drive Neopixels. They take 24 PWM pulses per led, and chain from one to the next; my current board has 6.

    I set up the FlexPwm to idle low, create an array in memory...
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    T4 UART Rx DMA -Disable the Rx FIFO!

    Just a head's up: If you're going to DMA data from a T4 UART, disable the UART FIFO during setup!

    LPUART2_FIFO &= ~LPUART_FIFO_RXFE;

    Longer version:
    I've returned to working on a...
  6. I like tni's comment better than my own!

    <Snipped> I like tni's comment better than my own!
  7. Consider having the input line interrupt on the...

    Consider having the input line interrupt on the rising edge, as a highest-priority interrupt, and grabbing the SYSTICK value. In your interrupt handler, grab SYSTICK first thing, and then re-enable...
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    I've seen references to the need for a...

    I've seen references to the need for a current-limiting resister between the drive and the first LED. 300-500 ohms are the values I've seen. Look at Adafruit's documentation for their neopixel...
  9. It's always helpful to have all the code. In this...

    It's always helpful to have all the code. In this case, the definition of HG_Out_Buffer.

    But I suspect from the compiler errors that it's defined as a char array. Probably the easiest way to fix...
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    Keep in mind that rad is not a "10k and it dies"...

    Keep in mind that rad is not a "10k and it dies" sort of thing. It's a curve; some devices fail after 1k and some are still alive after 50k. And the failures can be very subtle. You'll want to...
  11. DMA both Tx and Rx, with a parallel Interval...

    DMA both Tx and Rx, with a parallel Interval Timer on the Rx side so you know if you've missed part or all of a message. I'm assuming the messages are always of known length. Having messages just...
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    I don't think Paul charges enough for his...

    I don't think Paul charges enough for his products. I'm not kidding. It's a Cadillac product, with Cadillac support.
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    enum creates compile-time values, very roughly...

    enum creates compile-time values, very roughly like a #define. A struct also creates a compile-time definition, but this definition can be instantiated (which is where you start to use memory).
    If I...
  14. Assuming the SD top isn't oily, try a daub of red...

    Assuming the SD top isn't oily, try a daub of red nail polish instead
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    Lest it be thought this is all theoretical, this...

    Lest it be thought this is all theoretical, this is an issue I'm facing today:
    * I'm receiving async data from an external servo using DMA
    * I want to run an interval timer during the receive in...
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    Nice article! And this is the answer I was...

    Nice article! And this is the answer I was looking for, smart interrupt re-enable without the stack use of my example. Here's the pertinent code snippet from the article:

    uint32_t prim;
    ...
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    It's been a while since I've looked at the M4...

    It's been a while since I've looked at the M4 registers, but I *think* you can create an inline assembly routine that grabs the status and returns it. I'll try to find my code...
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    If you call from an ISR a routine that itself...

    If you call from an ISR a routine that itself does the disable -- enable sequence, you'll be returning to the ISR with interrupts enabled. Probably it will be ok. But if someone calls the routine and...
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    I was going to suggest this approach: Enter safe...

    I was going to suggest this approach:
    Enter safe area:
    * Push the interrupt status register
    * Disable interrupts

    <Do what is needed>

    Exit the safe area:
    * Pop the interrupt status register
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    Thread safety, please...

    I've been thinking a lot about the potential of the Teensy 3.5 & 3.6, and their potential for preemptive schedulers. I've written such schedulers in the past on microprocessors with less capabilities...
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    I wouldn't expect a Teensy T-shirt to fit me...

    I wouldn't expect a Teensy T-shirt to fit me...
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    Paul, Robin, I'm so pleased to see your success!...

    Paul, Robin, I'm so pleased to see your success! Congratulations on the results of your hard work!
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    "Soldering Goddess Erin"! I'd call her Eagle-Eyes...

    "Soldering Goddess Erin"! I'd call her Eagle-Eyes Erin! I can barely see the leads on the 3.2 board - I don't know how you two solder those Teensy things!
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    A: 0.300 b: 0.380

    A: 0.300
    b: 0.380
  25. One of the things I like about the Teensy's are...

    One of the things I like about the Teensy's are the multiple serial ports. I wanted logging for a project I'm working on, wired up Serial 1 to a FTDI cable, opened a serial monitor within the Arduino...
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    Figured it out, with some clues from a much...

    Figured it out, with some clues from a much earlier post.

    Drops a byte: Set up DMA, enable UART Tx, start DMA.

    Works perfectly: Set up DMA, start DMA, enable UART Tx.
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    You've defined Note_event as 15 x 1, but you're...

    You've defined Note_event as 15 x 1, but you're using it as 15 x 2.

    I would define a structure containing all the items you need for a data event, and then instantiate an array of these. This...
  28. I think if you're looking for a monitoring shift...

    I think if you're looking for a monitoring shift register you're headed toward FPGA-land.

    Have you considered the 74AHC674? It's a 16-bit parallel-in, serial-out shift register. I haven't looked...
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    @mlu: I agree with you that the point of maximum...

    @mlu: I agree with you that the point of maximum slope of a sine wave is the zero-crossing. I submit to you that this is also the point of the waveform with the worst SNR. JohnKon's comment <quote>I...
  30. You might consider using a 74AHC373, which would...

    You might consider using a 74AHC373, which would let you read 8 data bits at a time. D5 (MSB), D21, D20, D6, D18, D19, D14, D2 (LSB) work nicely as a multiplexed data/address bus, and properly wired...
  31. Consider amplifying the signal before applying it...

    Consider amplifying the signal before applying it to the Teensy. As a digital environment 10 mV is probably in the noise.
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    Just a comment: The zero-voltage crossing is the...

    Just a comment: The zero-voltage crossing is the worst possible point in the waveform to look for a boundary condition, as the signal-to-noise ratio is no-signal, all-noise.

    In the DSP world you'd...
  33. I went down the "B" certification path in the...

    I went down the "B" certification path in the early '90's. <sarcasm> I'm sure it's gotten simpler since then! </sarcasm>

    I ended up working with a company that walked the product through the...
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    Vector: Done! I recently uncovered the forum...

    Vector: Done! I recently uncovered the forum conversation of a few years ago about this, and it was on my To-Do list

    NBYTES_SMLOE --> SOFF: Done! No change - still missing the 2nd byte of the...
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    Sometimes you just need to ask for help...

    I'm working on a DMA-based AX-12 servo driver. This implements a half-duplex async interface to the servos.

    I've gotten the TX side working. Well, almost. when I look at the data stream with a...
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    I've recently been re-discovering the joys of...

    I've recently been re-discovering the joys of DMA, so let me know if I can help.

    Although my initial version will only send one byte per dma request. I have some bit fiddling to do as yet...
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    A dumb question: Don't these detectors act as a...

    A dumb question: Don't these detectors act as a variable resister? So you put a voltage across them, through a resistor, and measure the voltage across the resistor? Here's a picture
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    It's not sending slashes, it's sending control...

    It's not sending slashes, it's sending control characters (like \n, newline). These are appearing because you used println rather than print.

    But! You need delimiters between your numbers, right?...
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    My original question was hardware related, but...

    My original question was hardware related, but the software-related comments have been interesting.

    I'm fascinated by the immensely capable K20 (Kurt - this is your fault! Your TR posts are...
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    The buffer part numbers are what I was looking...

    The buffer part numbers are what I was looking for - thanks! The 74LS241 takes me back - I was using it in a design over 25 years ago.

    Wee you able to drive 18 servos with the 74LS part? I'd...
  41. Odd question #2: What programs do you use for schematic capture and board layout?

    I used Orcad ages ago, but want something free
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    Driving ax-12 servos

    How do you drive these servos? I don't see any direction-switchable buffers that I like.

    Driving 18 servos, async 8N1 at 1Mb/sec. It seems like a lot to ask of one of the Teensy's Tx I/O pins. And...
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    I know, I know! I'll be porting my modified...

    I know, I know! I'll be porting my modified version of the TR code to the Teensy, which you've already done. But then I want to take advantage of the K20's DMA, build a preemptive scheduler for DMA'd...
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    Both very interesting. The fun for me is in the...

    Both very interesting. The fun for me is in the "doing"; I'd rather write and debug my own code than run with someone else's. It's not rational or efficient, but this is just a hobby for me.

    Much...
  45. I love the color of that board! I'm having too...

    I love the color of that board!

    I'm having too much trouble with my "Kid in the candy store" syndrome, but looking at your board reminded me of my end-game. I've realized that 18 servos add up to...
  46. I ordered this...

    I ordered this. I'll park it on top of the PC alongside my desk. I needed a lot more light anyway. My desk is currently set up with only low levels of available light, to make using the monitors...
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    I wouldn't depend on getting a complete line at...

    I wouldn't depend on getting a complete line at any time. Tni has the right of it. And they call these things Streams for a reason - there's no guaranteed message boundaries.

    Just assemble the...
  48. You're going to laugh! The first thing I did...

    You're going to laugh! The first thing I did after I took a good look at Daniel's board kit was to order a table-mounted magnifying glass/light combination from Amazon. I would have needed it anyway...
  49. I used to fuss about scope-creep at work, but...

    I used to fuss about scope-creep at work, but now consider that to be minor compared to my hobbies!
  50. I wasn't aware those were out there! well, you...

    I wasn't aware those were out there! well, you learn something new every day.

    I need to prototype a parent board with more uarts and a few other odds & ends, and like the one I found better, but...
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