Zephyr i2s echo code channel number

[Lanz]

Hi,

Im currently adjusting this i2s sample code to work with my TAS2781 audio amplifier. The code works perfectly  but I just want to do a little adjustment on the channel number to 4 to give me a 64 ratio as per table 3(i2s nordic documentation) of the config clock set to "ACLK" using the settings below. Once I have change the channel from 2 --> 4 the code stop communication to the i2s channel.

I'm very new to this drivers and I would appreciate if you could suggest what I need to change on the macros below.

also, is there any plans to make the zephyr i2s drive to work with format "config.format = I2S_FMT_DATA_FORMAT_PCM_SHORT;"?

Lanz

[Kenneth]

Hello,

I would expect that you get an "Failed to configure streams:..." when trying to set NUMBER_OF_CHANNELS to more than 2, since 2 is the maximum supported.

Looking at the implementation of i2s_nrfx_configure() I can find it should return -EINVAL.

	if (i2s_cfg->channels == 2) {
		nrfx_cfg.channels = NRF_I2S_CHANNELS_STEREO;
	} else if (i2s_cfg->channels == 1) {
		nrfx_cfg.channels = NRF_I2S_CHANNELS_LEFT;
	} else {
		LOG_ERR("Unsupported number of channels: %u",
			i2s_cfg->channels);
		return -EINVAL;
	}

Kenneth

[Kenneth]

If you want to change the ratio, I guess you need to modify the devicetree, e.g.:

&clock {
    hfclkaudio-frequency = <11289600>;
};

[Lanz]

Hi,

below is my setting for ACLK. from the photo It should be possible to get 64 as a ratio for 16 bit (4channels)? As you mentioned the configured function above is limited to 2 channels.?. 

[Kenneth]

There is no direct relationship between the confguration of #bitwidth and #channels vs. clock ratio. Instead looking at the code and i2c_nrfx.c I can find there is a function find_suitable_clock() that calculate the ratio that best fit the requested sampling frequency vs. hfclkaudio-frequency. I can only assume by your description that this function allways calculate 32x?

Kenneth

[Lanz]

Hi Ken,

yes the ratio is 32.. I have successfully sync the i2s comms of the nrf and the tas2781.. thanks for taking sometime to respond on my inquiries

Lanz