Instruction Trace on the LPC551X family

[lilly1337]

Hi,

I'm currently stuck on a problem where I would love to get instruction tracing up and running on the LPC5516 that we're using.

The user manual for the chipset states that it is supported (page 1074):
> Trace port provides Cortex-M33 CPU instruction trace capability. Output is via a serial
wire viewer.

But that is about everything I've been able to find out so far. As the ETM component - that I would have expected used for this - isn't listed in the CoreSight ROM table, I'm a bit stumbled on how to get this up and running.

For reference: I'm using a SEGGER J-Link BASE compact with PyOCD and JLink currently.  

[Alice_Yang]

Hi @lilly1337 

John is right.

Additionally, if you use MCUXpresso IDE, there is a SWO Trace Guide in the IDE installation path. You can refer to it.

“

You can use the SWO Trace functionality of MCUXpresso IDE with all supported debug solutions. However,
SWO requires connection to the target MCU using a compatible debug probe such as:
• LinkServer LPC-Link2 (standalone or built into many LPCXpresso development boards and some iMX RT
EVK boards)
• LinkServer MCU-Link / MCU-Link Pro (standalone or built into development boards)
• SEGGER J-Link
– All standalone versions but refer to SEGGER's website for details

”

Thank you.

BR

Alice

[John217Ross]

Hello!

The LPC5516 supports instruction tracing via its Serial Wire Output (SWO), which is a different mechanism from the ETM, explaining why you don't see the ETM in the CoreSight ROM table. To get this working with your J-Link and PyOCD setup, you must first ensure the physical SWO pin is connected. Then, configure your tools (either J-Link Commander or PyOCD) to enable SWO tracing and set the correct clock frequency, which will allow you to capture the trace output. 

[lilly1337]

Can you give me more details to specifically instruction tracing? As far as I can find (I've also taken a look at the MCUExpresso SWO Tracing Guide), you support all kinds of tracing, but not instruction tracing. And as far as ARM CoreSight goes for instruction tracing at least a ETM or MTP is required. What happens with the output and how it is further processed is decided by the TPIU - which can include SWO.

[Alice_Yang]

Hello @lilly1337 

The LPC551x supports the Instrumentation Trace Macrocell (ITM), which is implemented via Serial Wire Output (SWO). The ITM block provides a mechanism for transmitting data from your target to the debugger through the SWO stream.

This communication is achieved via a memory-mapped register interface. Data written to any of the 32 stimulus registers is forwarded to the SWO stream.

Detail usage please refer to the User Guide I attached last time.

BR

Alice

[lilly1337 · Accepted solution]

Okay thank you. Than it is as I already assumed to be, that the LPC551X does not support instruction tracing. But I would recommend NXP to change their wording here, as the ITM has absolutely nothing to do with instruction tracing - which is a specific thing in ARM - and as such the Datasheets or User Manual of the MCUs feel like false advertisement to me.

With best regards
Lilly