Analog Audio Output Frequencies

Hi there,

I am currently designing a program for the Jetson which produces an audio output. This output needs to be analog, as the resulting signal will be processed with some analog filters. From what I can tell, the sampling rate limit for PCM signals on the TX2 is 192kHz. The output will likely need to use frequencies higher than this sampling rate can provide. I was wondering if there is anyway to increase the sampling rate on the Jetson to output higher frequency signals. If not, would it be possible to connect the Jetson to a sound card with a higher output sampling frequency?


I doubt the internal sample rate can be increased as this is related to hardware. Maybe, but I don’t know of such a thing.

Any sound card which works on a desktop PC, and in which the card does not require any drivers not in the existing 4.4 series kernel, should probably work. You might have to add the driver and/or user space software, but it is likely a lot of PCIe audio cards will work (just be careful they don’t have some sort of power requirement the power supply can’t handle).

Maybe someone who has actually added a secondary audio card which worked could comment.

Thanks linuxdev,

Do you know if there is any way to directly output audio in an analog format from the TX2? Like a pin/connection which just outputs the PCM signal. Going from this document on page 50, it appears that there are several methods which can sample at 192KHz. However, those listed seem to be digital formats, such as USB audio. I would like the analog output so that I can directly provide the audio signal from the Jetson in the case I don’t use an external sound card.

You are looking for a DAC (digital to analog), but the Jetsons do not have this natively. There is i2s output, and you could think of this as a more complex version of PCM, but I do not know of any direct PCM output. I’m not an expert on this, but it sounded like you want over 192KHz sample rate, and this does not seem to be supported directly without extra hardware. Someone else would need to answer, but I doubt you can do what you want without adding hardware.

Thanks linuxdev,
I’ll have to do the DAC stuff externally then. Do you know if I can use the 192KHz rate for an oversampled version of a baseband signal which may not necessarily be a sound signal? I’m wondering if this output is only designed for typical audio signals.

I’m not sure I can answer this, I can only add some thoughts about it. Internally, when audio is expected, then often a certain bit width or rate is set up such that when serialized the most significant bit is sent first, and if the user of the data reads all bits, then it would be lossless. However, it is expected that whoever reads/uses those bits only wants to read fewer bits, then only the least significant bits are lost. I’m not sure what stages internal to various hardware might drop least significant bits, and this might be dropped in unexpected places. Should you buy extra hardware, and if that hardware is marketed for audio, then you would need to pay attention to this.

On the other hand, an expansion DAC, perhaps multichannel, when not marketed for use with audio drivers, very likely is lossless and won’t drop least significant bits. You’d have to read the documents on that hardware. You could use this to output PCM from somewhere internal which is audio, and simply read all bits and then you’d know it was lossless. Unfortunately, I do not have enough knowledge to give you specific cases or hardware.

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