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    Implementing I2C Slave on T3.2

    Hi All.

    Got question about implementing an I2C slave on T3.2. One common I2C technique is for the master to start a Read transaction and then proceed to read an arbitrary number of bytes from the...
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    Switch I2S Timing Source on the Fly

    Hi All.

    I have a need in my project to periodically switch the timing source (on the fly) of the I2S Tx from an externally supplied MCLK to the internal one generated by Fractional Clock Divider...
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    Here's what I found and ordered:...

    Here's what I found and ordered: http://store.sure-electronics.com/product/AA-AB32255. It looks promising. The TI chip appears capable but quite complex. It has significant Audio DSP abilities that...
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    So have I. But, it has analog inputs. I'm looking...

    So have I. But, it has analog inputs. I'm looking for I2S.
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    I already have that. Now I'm looking for an...

    I already have that. Now I'm looking for an integrated, digital-to-the-final-chip solution.


    Already thought of that. But, fabbing the PWB and buying the BoM for a onesie-twosie production run...
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    It does, just as I mentioned. * There's no...

    It does, just as I mentioned.


    * There's no "buy" button on the web site I linked.

    * I've entered an RFQ on the web site --- no reply.

    * I've sent multiple emails to their "Customer...
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    20W I2S Audio Amplifier Board

    Anyone know of a ~20W / channel stereo I2S Class D amplifier board? Having I2C control for configuration and volume control would be an extra bonus. A manufacture’s Eval Board showcasing their chip...
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    Without thinking about it too much, it seems...

    Without thinking about it too much, it seems you'd be better off using one of the K20's FTMs set up for Input Capture mode.
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    Interfacing 32Fs I2S CODEC

    Hi All.

    I’m thinking about interfacing Adafruit’s MP3 CODEC Breakout to the I2S Input of T3.X boards and the Teensy Audio Library.

    This breakout uses the VS1053B from VSLI Solution. Even though...
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    Yes, I am familiar. Thank you.

    Yes, I am familiar. Thank you.
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    Thanks @KurtE. So, looking at the T3.6 schematic...

    Thanks @KurtE. So, looking at the T3.6 schematic (but not yet the code), it seems that using its built-in SD card with the Audio Library will use the chip’s HDSC controller rather than SPI. And, I...
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    Audio Library, SPI Peripherals, and T3.6

    Hi all.

    So, working on a project using T3.2 that uses both the AudioPlaySdWav class from the Audio library and an nRF24L01+ module. I’m having problems with the code hanging and my conjecture is...
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    Yes, an array of HardwareSerial pointers works...

    Yes, an array of HardwareSerial pointers works fine as long all “SerialX” objects are instances of that class. The advantage there is that HardwareSerial defines the .begin() method so you can loop...
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    Something like this. Compiles for a T3.5, but I...

    Something like this. Compiles for a T3.5, but I don't have one to test it.

    Stream *streamArray[] = {&Serial, &Serial1, &Serial2, &Serial3, &Serial4, &Serial5, &Serial6};
    const uint8_t numSerials...
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    Nice. Thanks Paul.

    Nice. Thanks Paul.
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    It's probably more flexible to use a an array of...

    It's probably more flexible to use a an array of pointers to Stream objects.
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    Port Pin Edge Detection

    Hi All.

    I’m wondering if it’s possible to use the edge detect capability of T3.2 Port Pins without actually causing an interrupt. I don’t want to miss the signal edge, but I don’t need the fast...
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    So, if I'm reading the datasheet and source code...

    So, if I'm reading the datasheet and source code correctly, it looks like the Baud is actually set to 3.75 MHz on a T3.2 (overclocked) when Pin 8 / UART2 is selected. Right?
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    Thanks Paul. I was just about to post that I...

    Thanks Paul. I was just about to post that I found that info after digging through the datasheet for a while.
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    WS2812Serial Question

    Hi All:

    Is seen in the example code for the WS2812Serial libary the following line:

    // Teensy 3.2: 1, 5, 8, 10, 31 (overclock to 120 MHz for pin 8)
    Just curious why the need for 120 MHz...
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    If the duty cycle is fixed at 50%, how is it PWM...

    If the duty cycle is fixed at 50%, how is it PWM (Pulse Width Modulation)?
  22. Thread: DMA llibrary

    by gfvalvo
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    Have you looked at the DMAChannel class that...

    Have you looked at the DMAChannel class that comes with the Teensy core?
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    I'm currently driving APA102 LEDs programmaticly...

    I'm currently driving APA102 LEDs programmaticly with 24 MHz SPI (fastest possible on T3.2) -- no issues. The advantage of DMA is being able to update a buffer with the next display (ping-pong style)...
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    I’ll probably try to link 2 DMA channels to do...

    I’ll probably try to link 2 DMA channels to do the SPI TX part.

    The first channel will trigger from the SPI TX FIFO Not Full (TFFF) and will do a 16-bit transfer from the next buffer location to...
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    Well, I think I have an explanation for the noted...

    Well, I think I have an explanation for the noted behavior - at least a “Handwaving” one. It appears to me that the upper 16 bits of the PUSHR register (the command word) are not “sticky”. By this I...
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    I haven’t carefully quantified it yet, but the...

    I haven’t carefully quantified it yet, but the gap does vary when using DMA. Seemed to range from high 100’s to low 200’s (ns). I was only sending 151 bytes, so 32767 byte threshold did not come into...
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    So, the plot thickens. I switched over to the...

    So, the plot thickens. I switched over to the non-DMA overload of ‘transfer()’:

    void transfer(const void * buf, void * retbuf, size_t count);
    After this, two very interesting things happened:
    ...
  28. You can also instantiate an array of objects...

    You can also instantiate an array of objects directly:

    #include "Arduino.h"
    #include "MIDI.h"

    midi::MidiInterface<HardwareSerial> interfaceArray[] = {
    { Serial1 }, { Serial2 }, { Serial3 },...
  29. I know nothing of MIDI. But, using standard C++...

    I know nothing of MIDI. But, using standard C++ techniques, you can define your array of MIDI object pointers like this:

    #include "Arduino.h"
    #include "Audio.h"
    #include "MIDI.h"
    ...
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    Hi @KurtE. So, upon further examination of the...

    Hi @KurtE. So, upon further examination of the datasheet, things don't seem to be adding up. More specifically, they're not adding up to the amount of inter-frame gap shown in both of our...
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    Thanks again!!!

    Thanks again!!!
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    Thanks @KurtE. For my own edification, I'll dig...

    Thanks @KurtE. For my own edification, I'll dig into the SPI and DMA sections of the chip manual again. It's been a while. As far as you know, would a ~200ns gap be in the ballpark for 24MHz clock...
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    DMA SPI on T3.2

    Hi all. I decided to try driving an APA102 LED strip using DMA-based SPI on a T3.2. I’m using the standard SPI library that comes with Teensyduino. My code loads up the DMA buffer, calls...
  34. Here's an application where I synced the FTM to...

    Here's an application where I synced the FTM to an external signal - https://forum.pjrc.com/threads/55148-AC-Mains-Cycle-Phase-Control?highlight=phase
    It's a different application, but maybe you can...
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    Thanks Paul.

    Thanks Paul.
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    Can You "malloc()" DMAMEM?

    So, the DMAMEM directive is available to specify at compile-time time that a variable is to be stored in the lower RAM block. I'm wondering if there's a way to do the same thing with a dynamic...
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    OK, I just re-read your original post. I see...

    OK, I just re-read your original post. I see you're actually supplying a pointer to a HardwareSerial object. It was a little confusing since you named it "stream". I misread that as the class Stream....
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    That's fine, but the code to do that register...

    That's fine, but the code to do that register manipulation doesn't belong in your XXX class. Since the class deals with a Stream pointer, it should only do things that Stream knows about. The...
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    Trouble is, your starting philosophy is wrong....

    Trouble is, your starting philosophy is wrong. The purpose of the Stream class is to handle the I/O without regard to the underlying hardware (could be USB, HardwareSerial, SoftwareSerial, etc). The...
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    Since FTM0 has 8 channels, you could implement...

    Since FTM0 has 8 channels, you could implement similar capability on that (FreqCount uses the LPTMR). See the processor's Datasheet.

    EDIT:
    Sorry, that's wrong. The FreqCount technique clocks the...
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    Maybe try bypassing the analogWrite() function...

    Maybe try bypassing the analogWrite() function and instead manipulate the FTM directly? First, in your setup() function, configure the FTM for the appropriate frequency / resolution. Then configure...
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    So, I've been playing around with a T3.2 (only...

    So, I've been playing around with a T3.2 (only Teensy I have on hand right now). I still think @ jofre's problem statement is not completely defined. First, if the experiment can really produce even...
  43. Idea for FTM Application - Is a Race Condition Possible?

    Hi All.

    As I was thinking about a solution to a question posted in another thread, I wondered if it would be possible to extend the input capture capability of a T3.2/5/6’s FTM to 32-bit values...
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    I recommend using an FTM and asked several...

    I recommend using an FTM and asked several pertinent questions in @jofre's nearly identical thread on the same topic. So far, no reply to my questions.
  45. Might be time to put a scope on the SDA and SCL...

    Might be time to put a scope on the SDA and SCL lines.
  46. Thread: Photon Counter

    by gfvalvo
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    Don't know if will work, but I'd look into using...

    Don't know if will work, but I'd look into using the input capture capability of a T3.6 Flexible Timer Module (FTM).

    First though, your "Requirements Document" needs to be fleshed out quite a bit:...
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    T3.2 Power Fuse Rating

    Hi all, got a quick question. The schematic for T3.2 shows a fuse between the Micro-USB connector and the VIN / VUSB pins (as well as the voltage regulator):
    16614
    There are times, especially...
  48. Thread: String issue..

    by gfvalvo
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    I'm confused about why you would do this in the...

    I'm confused about why you would do this in the first place. What is the expected result of attempting to change a literal constant?
  49. You could have your Term class inherit from...

    You could have your Term class inherit from Stream and implement the special functions as required:

    #include "Arduino.h"

    class Term: public Stream {
    public:
    Term(Stream *p) :...
  50. It might be good if you told us what the traces...

    It might be good if you told us what the traces in the scope shot are along with the horizontal scale. Also, perhaps provide a schematic or block diagram. And, a clear drawing of what you want the...
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