Tracing on Nordic Semiconductor nRF52840
This article describes how to get started with trace on the Nordic Semiconductor nRF52840 series. This article assumes that there is already a basic knowledge about trace in general (what is trace, what different implementations of trace are there, etc.). If this is not the case, we recommend to read Trace chapter in the J-Link User Manual (UM08001). The Nordic Semiconductor nRF52840 series implements tracing via pins only, so a J-Trace is needed to perform tracing on these devices.
In order to use trace on the Nordic Semiconductor nRF52840 series devices, the following minimum requirements have to be met:
- J-Link software version V6.32d or later
- Ozone V2.56n or later (if streaming trace and / or the sample project from below shall be used)
- J-Trace PRO for Cortex-M HW version V1.0 or later
The following sample project is designed to be used with J-Trace PRO and Ozone to demonstrate streaming trace. The project has been tested with the minimum requirements mentioned above and a nRF52840-DK (PCA10056). The sample project comes with a pre-configured project file for Ozone that runs out-of-the box on any Nordic Semiconductor nRF52840 that has the Tracepins connected. In order to rebuild the sample project, SEGGER Embedded Studio can be used.
Note: The example is shipped with a compiled .JLinkScriptfile, should you need the original source it can be requested at email@example.com
To create your own .JLinkScriptfile you can use the following project as reference: Tracing on SEGGER_Cortex-M_Trace_Reference_Board
The Nordic Semiconductor nRF52840 MCU uses a traceclock that is independent from the CPU clock. By hardware it is limited to maximum 16 MHz TCLK.
Note:The nRF52840-DK (PCA10056) has a switch SW7 that determines if the trace pins are shared with other functionality e.g. Buttons. To make sure that no accidental button presses stop your trace stream we recommend setting SW7 in the Alt. position.
Note: The 19-pin trace interface is not soldered on the target board by default. This needs to be assembled first.
Reference trace signal quality
The following pictures show oscilloscope measurements of trace signals output by the "Tested Hardware" using the example project. All measurements have been performed using a Agilent InfiniiVision DSO7034B 350 MHz 2GSa/s oscilloscope and 1156A 1.5 GHz Active Probes. If your trace signals look similar on your trace hardware, chances are good that tracing will work out-of-the-box using the example project. More information about correct trace timing can be found at the following website.
The rise time of a signal shows the time needed for a signal to rise from logical 0 to logical 1. For this the values at 10% and 90% of the expected voltage level get used as markers. The following picture shows such a measurement for the trace clock signal.
The setup time shows the relative setup time between a trace data signal and trace clock. The measurement markers are set at 50% of the expected voltage level respectively. The following picture shows such a measurement for the trace data signal 0 relative to the trace clock signal.