USBD example + CDC ACM example

RE: USBD example + CDC ACM example

ovrebekk — Thu, 03 Dec 2020 08:05:54 GMT

The limit depends primarily on which host OS you are using. In Windows we have found the CDC example to support data rates up to about 200kB/s (or 1600kbps).

So up to 200 bytes every millisecond should be possible.

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RE: USBD example + CDC ACM example

alexlöddeköpinge — Wed, 02 Dec 2020 07:42:57 GMT

[quote userid="2116" url="~/f/nordic-q-a/68866/usbd-example-cdc-acm-example/282713#282713"]This shouldn't be a problem, assuming you only have a couple of bytes of data to send for every sample. [/quote]

I have more than a couple of bytes to send every sample. What is the limit of CDC ACM?

I think that CDC ACM is not enough, for this reason I thought to use bulk endpoint. I think that it's the most suitable solution in my case.

Thank you so much,

RE: USBD example + CDC ACM example

ovrebekk — Tue, 01 Dec 2020 14:56:11 GMT

This shouldn't be a problem, assuming you only have a couple of bytes of data to send for every sample.

I would recommend buffering multiple ADC samples into larger packets before sending it over the USB if you can, in order to make the data transmission more efficient.

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RE: USBD example + CDC ACM example

alexlöddeköpinge — Tue, 01 Dec 2020 07:49:26 GMT

I have to send from ADC to PC a signal sampled at 1kHz.

RE: USBD example + CDC ACM example

ovrebekk — Tue, 01 Dec 2020 07:30:38 GMT

The CDC ACM class is also based on bulk transfers, so I don't think that should be an issue.

An important aspect of bulk data is that you are not guaranteed to get a packet through on every USB event (every millisecond), but you are guaranteed that all data will be transferred eventually.

How much ADC data do you need to send every second?

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RE: USBD example + CDC ACM example

alexlöddeköpinge — Mon, 30 Nov 2020 15:53:04 GMT

Thanks for your answer,

I have to implement a composite device. I use the CDC ACM class to transfer from nrf52840 to pc a low-speed signal.

I also need to transfer data from ADC to PC and I want to do this using bulk transfer. I need bulk transfer because I want to transfer packaged real-time data.

RE: USBD example + CDC ACM example

ovrebekk — Mon, 30 Nov 2020 15:41:48 GMT

Is there any reason you need to merge these two examples?

What do you miss from the USBD example that you don't get in the CDC ACM example?

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