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    For Teensy 4.0 core code, I believe that the only...

    For Teensy 4.0 core code, I believe that the only thing from not using the DSB will be just that sometimes the internal ISR is called but it does not find any GPIO pin which triggered the interrupt,...
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    Also, I've just checked Paul's source code of...

    Also, I've just checked Paul's source code of Teensy 4.0 core, and it seems like that the internal GPIO ISR does NOT use asm("dsb"). Perhaps the internal ISR would also need it, to prevent such...
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    Yes, my 74LVC is on 3.3V :) I added ...

    Yes, my 74LVC is on 3.3V :)

    I added
    asm("dsb");
    .. and it changed the behavior! Every time the ISR is called, the corresponding bit on GPIOx_ISR is set to 1!

    Would you mind explaining a...
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    Unfortunately my old computer is a rarer one... I...

    Unfortunately my old computer is a rarer one... I tried to find the schematics from the web several times, but only found that others said it was not available anywhere... :(
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    The input to my 74LVC buffer (whose output is...

    The input to my 74LVC buffer (whose output is directly connected to Teensy's pin 29) is from an old 8-bit computer, which uses TTL level gates. So I guess I can't post its schematics... but it...
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    Cause I can't do soldering where I am at right...

    Cause I can't do soldering where I am at right now, I've tried to use INPUT_PULLUP (with the original signal still connected) on the pin, as follows:



    void setup() {
    pinMode(PIN,...
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    Then, perhaps the guess is that when the signal...

    Then, perhaps the guess is that when the signal is not clean (eg floating), such a weird behaviour may happen (ISR called without the GPIOx_ISR bit set) ... ? The signal into 74LVC is from some...
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    I indeed had used the...

    I indeed had used the pinMode+attachInterrupt+settting _VectorsRam[...] method earlier. To make it sure, I've just replaced the whole content of setup() by


    pinMode(PIN, INPUT);
    ...
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    The strange output is shown only when I connect...

    The strange output is shown only when I connect PIN 29 to a signal which frequently activates (roughly 1Mhz~500Hz range). I don't have any pullup/down. Could this be related to signal quality..?
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    I believe that the pin is enabled for input by...

    I believe that the pin is enabled for input by default --- Just in case, I've just added
    pinMode(PIN, INPUT); at the beginning of setup(), and confirmed that the behaviour is the same.
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    I'm aiming to a very time-critical application,...

    I'm aiming to a very time-critical application, so I need to handle the interrupt directly. Yes, the arduino-way would not show this strange behaviour, because Paul's internal ISR checks the bit in...
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    Mysterious interrupts on Teensy 4.0

    Hi all,

    I found the following strange behaviour when I was testing Teensy 4.0's GPIO interrupt, handling it directly.

    When a GPIO interrupt is activated, a bit in GPIOx_ISR corresponding to the...
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    Yes, the input data sampling can be done...

    Yes, the input data sampling can be done separately at different frequency. It was about reducing the latency of 128/44100 sec (= the playing time of one audio data block). Perhaps this might be...
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    I guess what I said above was not clear enough. ...

    I guess what I said above was not clear enough. Teensy is sampling (non-audio) input data from some other gpio pins, and the desired audio output is being generated from that input data: roughly,...
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    I guess the first is more likely. Teensy 4 can...

    I guess the first is more likely. Teensy 4 can handle a lot higher frequency interrupts (eg every 1/44100 sec), just by using IntervalTimer straightforwardly. 64/44100 sec is not difficult at all. ...
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    Yes, I had recompiled necessary things.

    Yes, I had recompiled necessary things.
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    Changing AUDIO_BLOCK_SAMPLES causes problem

    Hi,

    I am trying to use AudioOutputMQS of the audio library, with a smaller value of AUDIO_BLOCK_SAMPLES. I changed 128 to 64 in the line


    #define AUDIO_BLOCK_SAMPLES 128

    of AudioStream.h....
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