USBD example + CDC ACM example

[alexlöddeköpinge]

Hi everyone,

Is there any example that explain how to merge USBD example and CDC ACM example?

Thanks everyone,

BR

[alexlöddeköpinge]

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.

BR

[ovrebekk]

Hi 

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?

Best regards
Torbjørn

[alexlöddeköpinge]

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

[ovrebekk]

Hi

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. 

Best regards
Torbjørn

[alexlöddeköpinge]

ovrebekk said:

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

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,

BR

[ovrebekk]

Hi

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. 

Best regards
Torbjørn