Jetson Nano simple I2S driver

Robotics & Edge Computing Jetson & Embedded Systems Jetson Nano
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I am trying to figure out how to use I2S on my custom board with some differences that I am not sure how to resolve.

I have used on the raspberry pi compute module the “simple-audio-card” driver which allowed me to use any I2S device that was configured independently from the driver and then I could use ALSA library knowing the settings to capture the results (ADC is TLV320ADC5140). In other words, the driver didn’t manage the ADC settings since it was generic and I was expected to do that myself. Very simple to setup.

The driver I see for the TLV320ADCX140 uses I2C for configuration. For this board, I needed to use SPI. I am able to connect to the ADC and configure all the settings to set it into the mode I want with SPI. It felt like rewriting the whole TLV320ADCX140 to use SPI is a lot to take on.

What I cannot figure out is how to setup the Jetson Nano to receive this data with any sort of generic driver. I have the I2S port and SPI enabled using the HDR40 settings in the DTB (since that was the easiest way to set them up)

spidev0.1 → SPI of ADC
I2S4 connect to I2S of ADC

Is there a generic sound card interface I can enable to set I2S settings on the Jetson Nano side and capture without having to use a dedicated driver?

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I found this thread which makes it sound like as long as you configure yourself, you should be fine:

What is not clear to me is:

Who needs to be the master? ADC or Jetson Nano?
If it’s the Jetson Nano, how do you set the clock frequency coming out?

It seems like once I have this setup, I should be able to do:

arecord -D hw:tegrasndt210ref,0 -r 48000 -f S24_LE -c 4 -d 10 test.wav
arecord -D plughw:CARD=tegrasndt210ref,DEV=0 -r 48000 -f S24_LE -c 4 -d 10 test.wav

(Not sure which device name to use)

To test it. I’ve configured the ADC for
24-bit
I2S
48K

I’ve not changed the master mode yet, so that could be wrong.

3

Have you checked NVIDIA Jetson Linux Developer Guide : Audio Setup and Development | NVIDIA Docs?

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I had not come across this! Let me dig into it. Thank you. I will report back if I run into any issues.

5

I wanted to come back and say I got this working, and lots of posts on the site helped me.

For anyone wanting to not use a dedicated driver for an ADC/DAC, the simple driver that is installed by default works great.

In this case I was using SPI.

So first, I needed to setup the DMA mux and make sure I was in TDM mode (dsp-b) for this particular ADC.

alsactl init tegrasndt210ref
amixer -c tegrasndt210ref sset ‘ADMAIF1 Mux’ I2S4
amixer -c tegrasndt210ref sset ‘I2S4 codec frame mode’ dsp-b

I believe I can setup a configuration for this which I will likely do at some point, but this was to get going.

Now, if you are using I2C or SPI, you’ll need to configure your device for the setup you have. Since I cannot find a single ended DC example for this ADC, I will post what I used:

(the last parameter to spiADC is “isRead” so all these are writes)

// Wake up device
spiADC(FD_AUD,0x02,0x81,0);
spiADC(FD_AUD,0x02,0x81,0);
std::this_thread::sleep_for(std::chrono::milliseconds(10));
// TDM & 32-bit (I2S only supports 2 channels, need TDM which supports 4)
spiADC(FD_AUD,0x07,0x30,0);
// 0x13 we leave default, sets in slave mode
// Setup line inputs for all 4 channels (There are some gain settings did not touch on next addr)
spiADC(FD_AUD, 0x3C, 0xB0,0);
spiADC(FD_AUD, 0x41, 0xB0,0);
spiADC(FD_AUD, 0x46, 0xB0,0);
spiADC(FD_AUD, 0x4B, 0xB0,0);
//Turn off the HPF
spiADC(FD_AUD, 0x6B, 0x00,0);

// Enable all 4 ADC
spiADC(FD_AUD,0x73,0xF0,0);
// Enable ASI 4 output slots (not sure if I did correctly)
spiADC(FD_AUD,0x74,0xF0,0);
// Power up ADC and PLL (not sure if these are right)
spiADC(FD_AUD,0x75,0x60,0);

And that is it, now you can test with something like this:

arecord -D hw:tegrasndt210ref,0 -r 48000 -f S32_LE -c 4 -d 1 test.wav

And if you want to view that wav, install “sudo apt-get install audacity” and drag and drop to see the output.

For capturing in your own program, I recommend Tinyalsa which is easy to setup.

And that was it!

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