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

[matrixgti]

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 ?

Thanks

Flavio

[ESPsupport]

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.

[matrixgti]

Following my previous post I did some more test and build up an external amplifier but without success, I assume that the filtering part of the PWM signal was done onboard like in the Ulcd models but I found out that in the GEn4 the audio filter is not popolated on the PCB.
I'm not sure if audio generation on Diablo16 is the same as in Picaso. This is the result output with the scope (magenta --> AUDIO) (Yellow -> Ampli Output) and the schematic of my ampli.



Probably the filter combination is not good for Diablo16 output rathen then Picaso ?

Any help to get it working will be very apprecciated,

Thanks

Flavio

[ESPsupport]

You need to add the PWM filtering in front of your amp, as it mentions in the datasheet the PWM filtering is not on the board, and it shows this in the circuit. If it was done on the board it would mean 'audio' would be traveling down the flex which would be good for keeping it 'clean'.

There is a 'sample' filter in the reference design in the Diablo16 Datasheet.

[matrixgti]

You need to add the PWM filtering in front of your amp, as it mentions in the datasheet the PWM filtering is not on the board, and it shows this in the circuit. If it was done on the board it would mean 'audio' would be traveling down the flex which would be good for keeping it 'clean'.

There is a 'sample' filter in the reference design in the Diablo16 Datasheet.

Hi Mark, Thanks for the reply, could someone please give me a quick feedback on this filter/ampli configuration ? Audio and Audio_EN(able) comes from Ulcd flex , common GND and common 2A filtered 5v power supply.

Thanks

Flavio

[James_4DSystems]

Hi Flavio,

That circuit looks fine, looks to be the same as the circuit we provide for the MOTG-AC4 board, amongst others.

Regards