OrangePi Zero 2w and I2S: only left channel

General Discussion
1

Hi everyone,

I’m managed to play some audio using i2s and max98357a (violet board), but then I realized … I’m only playing the left channel.

With SD hanging (disconnected), I should be able to hear both channels, right? Eventually, I want to support 2 boards, one channel each, but I got stuck at the first step.

Here is my dts:

/dts-v1/;
/plugin/;
/ {
    compatible = "allwinner,sun50i-h616";
    fragment@0 {
        target = <&pio>;
        __overlay__ {
            ahub_daudio0_pins_a: ahub_daudio0@0 {
                pins = "PI0", "PI1", "PI2";
                function = "i2s0";
                drive-strength = <0x14>;
                bias-disable;
            };
            ahub_daudio0_pins_b: ahub_daudio0@1 {
                pins = "PI3";
                function = "i2s0_dout0";
                drive-strength = <0x14>;
                bias-disable;
            };
            ahub_daudio0_pins_c: ahub_daudio0@2 {
                pins = "PI4";
                function = "i2s0_din0";
	        drive-strength = <0x14>;
		bias-disable;
            };
            ahub_daudio0_pins_d: ahub_daudio0_sleep {
		pins = "PI0", "PI1", "PI2", "PI3", "PI4";
		function = "gpio_in";
		drive-strength = <0x14>;
        	bias-disable;
            };
        };
    };
    fragment@1 {
        target-path = "/soc";
        __overlay__ {
            ahub0_plat: ahub0_plat {
                #sound-dai-cells = <0>;
		compatible	= "allwinner,sunxi-snd-plat-ahub";
                apb_num		= <2>;	/* for dma port 5 */
		dmas		= <&dma 5>, <&dma 5>;
		dma-names	= "tx", "rx";
		playback_cma	= <128>;
		capture_cma	= <128>;
		tx_fifo_size	= <128>;
		rx_fifo_size	= <128>;
        tdm_num         = <0>;
        tx_pin          = <0>;
        rx_pin          = <0>;

		pinctrl-names = "default", "sleep";
                pinctrl_used;
		pinctrl-0 = <&ahub_daudio0_pins_a>, <&ahub_daudio0_pins_b>, <&ahub_daudio0_pins_c>;
		pinctrl-1 = <&ahub_daudio0_pins_d>;

                status = "okay";
            };
            ahub0_mach: ahub0_mach {
                compatible = "allwinner,sunxi-snd-mach";
		soundcard-mach,name = "ahubi2s0";
		soundcard-mach,format = "i2s";
                soundcard-mach,frame-master = <&ahub0_cpu>;
                soundcard-mach,bitclock-master = <&ahub0_cpu>;
                soundcard-mach,slot-num = <2>;
                soundcard-mach,slot-width = <32>;

		status = "okay";

                ahub0_cpu: soundcard-mach,cpu {
		    sound-dai = <&ahub0_plat>;
                    soundcard-mach,pll-fs   = <4>;
                    soundcard-mach,mclk-fs  = <0x100>;
		};

		ahub0_codec: soundcard-mach,codec {
		};
            };
            hdmi: hdmi@6000000 {
                status = "disabled";
            };
        };
    };
};

When running: speaker-test -D hw:1,0 -c 2 -t wav , I can only hear “Front left”.

Has anyone succesfully played stereo on a single board and using two boards?

Cheers!

2

Hello, first clear some misunderstanding:

It’s a mono amplifier, so with one board you will never get stereo. But you could play the same signal (if you have a stereo source: left, right or a mix of it) through two speakers, which is still mono because it’s exact the same signal without any stereo info.
So I assume you wanna play the mono signal through 2 speakers, not just one.
SD hanging/floating defaults to left channel

To get a signal through both channels the SD mode needs to be between ~0.16–0.77 V.

I’ve read about 0.5 V to get an even mix between left and right.

Sure, with two boards you can get true stereo, setting one to floating and the other to a voltage between 0.8 and 1.4 V

reference: https://wiki.dfrobot.com/SKU_DFR0954_MAX98357_I2S_Amplifier_Module#SD%20Mode

https://cdn-learn.adafruit.com/downloads/pdf/adafruit-max98357-i2s-class-d-mono-amp.pdf

https://www.analog.com/media/en/technical-documentation/data-sheets/max98357a-max98357b.pdf

3

I know it is mono, but it should be able to play (L + R) / 2.

I checked my boards with ESP32, and I’m able to select channels easily, so this must be a kernel/DTS or alsa issue. Considering I’m operating on hw devices, skipping the whole alsa setup, my wild guess is DTS?

4

Hello mtojek

In my script you can see some little difference , the part with it under this line

fragment@1 {
		target-path = "/soc";
		__overlay__ {
			ahub0_plat: ahub0_plat {
				#sound-dai-cells = <0>;
				compatible = "allwinner,sunxi-snd-plat-ahub";
				apb_num = <0>; /* for dma port 3 */
				dmas = <&dma 3>, <&dma 3>;
				dma-names = "tx", "rx";
				playback_cma = <128>;
				capture_cma = <128>;
				tx_fifo_size = <128>;
				rx_fifo_size = <128>;
				pinctrl-names = "default", "sleep";
				pinctrl_used;
				pinctrl-0 = <&ahub_daudio0_pins_a>, <&ahub_daudio0_pins_b>, <&ahub_daudio0_pins_c>;
				pinctrl-1 = <&ahub_daudio0_pins_d>;
				status = "okay";
			};
			ahub0_mach: ahub0_mach {
				compatible = "allwinner,sunxi-snd-mach";
				soundcard-mach,name = "soundbox";
				soundcard-mach,format = "i2s";
				soundcard-mach,frame-master = <&ahub0_cpu>;
			        soundcard-mach,bitclock-master = <&ahub0_cpu>;
			        soundcard-mach,slot-num = <2>;
			        soundcard-mach,slot-width = <32>;
				status = "okay";

				ahub0_cpu: soundcard-mach,cpu {
					sound-dai = <&ahub0_plat>;
					soundcard-mach,pll-fs = <4>;
				        soundcard-mach,mclk-fs = <0>;
				};

				soundcard-mach,codec {
				};
			};
		};
	};
5

After some test with my PCM5102A this morning
This is good for separate left and right channels
as well as stereo effects with test tracks under LMS and Squeezelight.

6

Thanks for sharing.

I see that your config does not define tdm_num and tx/rx pins, so probably you have warnings in dmesg. Considering your dts works well, it gives me more confidence that this must be a kernel issue, unless PCM5102A acts differently. I suspect that max98357a may accidentally get into TDM mode, which is useless in this case - we have just 2 channels.

7

Hello mtojek
Good point, I corrected the three lines

tdm_num         = <0>;
tx_pin          = <0>;
rx_pin          = <0>;

and no more messages in dmesg, thanks a lot
Otherwise, it doesn’t change anything for my PCM5102A and the stereo test sounds;
it still works with your fix.

Thank you :wink:

8

As I set, to do this you need to set it at around 0.5V and not let it float/hang, like they say in the linked official documentation of the board.

SD Mode

  • Turn off amplifier when SD is connected to GND(Voltage below 0.16V)

  • Output mix channel(Default) when the voltage on SD is between 0.16V to 0.77V, R1 resistance is 680k.

  • Output right channel when the voltage on SD is between 0.77V to 1.4V, R1 resistance is 330K.

  • Output left channel when the voltage on SD is over 1.4V, R1 resistance is 100K

9

I confirmed the voltage values with ESP32, but for some reason, there is no difference while running on Pi.