USBD CDC establishing connection has huge latency

RE: USBD CDC establishing connection has huge latency

Juliusc — Thu, 03 Feb 2022 18:40:37 GMT

I found somewhat of a solution or rather the inhibitory factor.

CDC will apparently stall after suspending and resuming the port if there's no continuous stream of data being written (at least in the beginning)

I put a for loop at the end of the initialisation which just sends a hundred empty strings over USB which leads to just milliseconds before my computer and other devices recognize the device as such.

connecting itself is similar. in my main state machine I have a case that says as long as Im not connected, send an empty string once in a while.

This is obviously kind of a dirty solution but since it doesn't interfere with business logic Ill leave it like this for now

RE: USBD CDC establishing connection has huge latency

Juliusc — Tue, 11 Jan 2022 10:22:32 GMT

id say around 20 seconds.

I think the firmware is doing fine so no delays in there, something must be up with the physical connection or maybe its on my mac?

RE: USBD CDC establishing connection has huge latency

Øyvind — Tue, 11 Jan 2022 10:10:58 GMT

Hello again,

How long does it take to establish the connection? Did you try with a clean CDC example from e.g. nRF5 SDK v17.1.0? What is your firmware doing at the time it is trying to connect?

Kind regards,
Øyvind

RE: USBD CDC establishing connection has huge latency

Juliusc — Fri, 07 Jan 2022 11:58:43 GMT

No the startup time is still way too long!

RE: USBD CDC establishing connection has huge latency

Øyvind — Fri, 07 Jan 2022 11:28:54 GMT

Does this mean that you have resolved this ticket?

RE: USBD CDC establishing connection has huge latency

Juliusc — Fri, 07 Jan 2022 11:26:13 GMT

sorry, fyi the softreset was my own fault, I called system_power_off() at one point

RE: USBD CDC establishing connection has huge latency

Juliusc — Fri, 07 Jan 2022 10:42:50 GMT

the existing project is my own, but I used the pre existing CDC example and embedded it into my own firmware!

SDK 15.3.0

also do you know If the CDC module make a softreset happen from time to time? I noticed that my uC just randomly restarts after a minute passes

RE: USBD CDC establishing connection has huge latency

Øyvind — Fri, 07 Jan 2022 10:33:14 GMT

Please provide more/relevant information on what SDK version you are working on.

Is this existing project your own or a sample from the SDK?

RE: USBD CDC establishing connection has huge latency

Juliusc — Fri, 07 Jan 2022 10:20:58 GMT

So Im not using the connect sdk and Im also not using Zephyr. I implemented CDC in an existing project that works with radar data.

Thanks for the reply

RE: USBD CDC establishing connection has huge latency

Øyvind — Thu, 06 Jan 2022 12:42:22 GMT

Hello,

From your previous ticket no 281204

Which version of the nRF Connect SDK are you using?

Have you checked out the standard cdc_acm sample in Zephyr?

If you look at the project configuration file and the main file you can usually get a good overview of which configuration settings and init code you need to use a specific feature, and you can copy paste it into your own project.

Just be aware that some of the config might be set already, and you should avoid duplication.

Kind regards,
Øyvind