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Gen4 Ulcd 70DT-AR Audio and Enable Audio strange behaviour

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  • Gen4 Ulcd 70DT-AR Audio and Enable Audio strange behaviour

    Hi All,
    I'm using an Gen4 Ulcd 70DT-AR that will be connected to a custom board with Atmega2560 (Arduino Code), and controlled by Uart. In this board I fitted an audio amplifier to be able to play wav sounds (like button click, alarms etc), before trying to connect the uLcd to my board I tried with GFX command and gen4-PA adapter to simulate all my object.
    Hooking a scope to Audio and Audio enable pins on gen4-PA I notice two strange behaviour, the first is that i have a lot of PWM spike even if the object Sound0 is in STOP , and also the Audio Enable pin start low ,but on first hit of play a file it go 3v3 and never go back to 0V, even on STOP or PAUSE.
    I tried two different uLcd display with same results.
    Do I have to set something special to enable the external audio ?



  • #2
    The amp is turned on when sound is first played, it is not turned off when the sound finishes, as a) this might cause a pop and b) it is assumed you might want to use the amp again.

    For certain audio rates / amplifiers and filter combinations this may result in continuous PWM 'noise'.

    I believe a call to pin_LO(AUDIO_ENABLE) will turn off the amp. If that doesn't work try pin_HI().

    I don't have a Gen4 with audio available to test here, but I'm pretty sure pin_LO() is the one.

    Why LO, when it sets the pin HI? That's because previous displays used LO for off and HI for on, so that 'sense' was retained for the command on Gen4.