RGB-Pi Scart Cable = no sound

Dancorp · January 27, 2019 at 8:16 PM

I would like to explain a problem that has been blocking my installation for many months.

I would like to install a RPi 3 in an old CRT TV, to create a Smart CRT TV and watch old stuff on it .

In order to have the best possible image quality, I use the famous RGB-Pi cable to output a RGB signal from the Pi (using a scart connector). (see http://www.rgb-pi.com)

There is a deditated distribution for this cable. On others, it is mandatory to set this configuration information in the config.txt to redirect A/V signals to GPIO.

For the video part, the cable designer has created a specific dtbo file.

On the audio side: the following information must also be added: dtoverlay=pwm-2chan,pin=18,func=2,pin2=19,func2=2

So I followed the instructions to adapt the librelec distribution by modifying the config.txt file

The video signal works well but no sound comes out... at all !

I have try to change all the settings, try to add audio addons... nothing works.

Since the official distribution rgb-pi works perfectly (dedicated to retrogaming), I wonder if there would be no conflict regarding GPIO ports used for the sound?

Good to know : Very very rarely during my tests, the sound worked. But a simple reboot and all is lost. (not reproducible sadly)

Thanks in advance for your help.

BR

Dan

**Da Flex** · January 27, 2019 at 8:40 PM Official Post

Maybe grab audio from the 4 poles jack.

**Klojum** · January 27, 2019 at 9:43 PM Official Post

Please don't use 'help' as a prefix in your titles. It would imply that we don't help in any other forum threads.

Dancorp · January 27, 2019 at 10:35 PM

it is the easy way out, but it will be very restrictive.

Indeed, I integrated the raspberry in the TV, and there are USB ports and a direct access to the micro SD card to change the distribution when I want it.

And the official distribution works very well via the GPIO.

If you help me find a solution, this can be very useful for all RGB-Pi users

**Da Flex** · January 27, 2019 at 11:28 PM Official Post

OK, your GPIO audio pins are 18 (GPIO_GEN5) and 19 (SPI_MOSI). Do you have this line in your config.txt?

Code

dtparam=spi=on

Dancorp · January 28, 2019 at 5:54 PM

Quote from Da Flex
OK, your GPIO audio pins are 18 (GPIO_GEN5) and 19 (SPI_MOSI). Do you have this line in your config.txt?
Code
dtparam=spi=on

No, that's not the case

I use the default config.txt and i add this settings

Code

dtparam=audio=on
dtoverlay=pwm-2chan,pin=18,func=2,pin2=19,func2=2
audio_pwm_mode=2

dtoverlay=rgb-pi
enable_dpi_lcd=1
display_default_lcd=1
dpi_output_format=6
dpi_group=2
dpi_mode=87
hdmi_timings=1920 1 152 247 280 240 1 3 7 12 0 0 0 60 0 40860000 1

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**Da Flex** · January 28, 2019 at 6:55 PM Official Post

Thanks. Please add my line for testing. I heard that newer kernels need that parameter to make SPI work.

Dancorp · January 28, 2019 at 7:53 PM

Thanks for the idea... Tested but no, it doesn't work

**Da Flex** · February 1, 2019 at 11:31 PM Official Post

I did some research, because your project is exotic and cool. Try this command to force PWM output. If it works, you can add it to autostart.sh. If it doesn't works, read the rest of the linked thread.

Dancorp · April 23, 2019 at 8:59 PM

Update : the issue is now solved on LE 9.x