USBD CDC establishing connection has huge latency

[Juliusc]

Hi, 

I have implemented the USBD CDC ACM driver into my firmware. What stands out is the latency as soon as the event 

APP_USBD_CDC_ACM_USER_EVT_PORT_OPEN 

triggers, my terminal emulator takes some time to actually establish the connection (i.e. until the communication channel can actually be used)

This must be related to the firmware since this happens on a macOS Terminal emulator as much as on a Windows emulator. 

What's happening in the background here?

BR

[Øyvind]

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

[Juliusc]

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

[Øyvind]

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?

[Juliusc]

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

[Juliusc]

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

[Øyvind]

Does this mean that you have resolved this ticket?

[Juliusc]

No the startup time is still way too long!

[Øyvind]

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

[Juliusc]

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?