What's difference between the Debug in connector (P18) and Trace connector (P25)?

[Hsu]

Hi Sir,

I'm studying the nRF52840-PDK, and i found there are two debug connector. One is Debug in connector (P18) and another is Trace connector (P25).

As check the pin define, P18 is 10-pin connector and P25 is 20-pin connector.

1. For software programming, when we should use debug in connector? and when we should use trace connector?

2. For project development, should I reserve these two interface in my project? If yes, any special tools I should install to use these two interfaces?

3. For programming usage, we only keep SWDIO/ SWDCLK/ VDD/GND as a 4-pin connector. But P18 has two more signal (SWO, reset), what's purpose for these two signals (SWO, reset)?

Thank you. BRs,

Hsu

[Jonathan]

The trace connector is used to trace, ie get to know which lines of your code got executed, profiling... It requires special hardware (like J-Trace).

[Hsu]

Hi Jonathan,

Thanks for your update, but if the P25 can use to trace the code, what is the purpose of the P18?

Han

[Jonathan]

This is pure speculation: P18 is for JLink 10 pins connector that you get on various probes, P25 is for the 20 pins variant found on JTrace-Pro. On JTrace-Pro, you get both the 10 pins and the 20 pins connector, the 20 pins connector includes all signals from the 10 pins one, plus extra lines for tracing.

[Hsu]

Hi Jonathan,

Thanks for your help, it makes me clear about this.