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raccoon

Beginner

Date of registration: Nov 29th 2017

Posts: 2

1

Wednesday, November 29th 2017, 2:31pm

RF interference

Hello to all SEGGER jedi masters!

A rather 'wonky' question:

Is it possible for a debugger, and its associated JTAG wiring, to create enough RF interference so that a target WiFi module would experience difficulties maintaining the connection to the access point?

I am working with USI's WM-N-BM-14, a WICED enabled module, and I currently experience frequent and non-deterministic connection losses when in debug mode.
On the contrary, with the production built, while keeping the debugger attached with no OpenOCD/GDB activity, the connection is stable.
The module supports 802.11b/g/n

There is yet the fact that a debug built is -O0, but I was just wondering if any of my fellow colleagues has some prior knowledge she/he would like to share!

Thank you for your time, let me know if you need more info!

(Disclaimer: My understanding of the physics related to RF is very limited ;( )

SEGGER - Nino

Super Moderator

Date of registration: Jan 2nd 2017

Posts: 430

2

Wednesday, November 29th 2017, 3:11pm

Hello,

Thank you for your inquiry.

Theoretically such an issue is possible and is highly dependent on how the JTAG lanes run through your device, how the RF module is shielded etc.
RF circuit design is a electric engineering specialization for a reason ;)

From a physics perspective every conductor with switched current acts like an "antenna" and emits electro- magnetic waves. These can interfere with other EM wave emitters like your Wifi Module. This is basically how the debug interface lanes could act on your target board if they have been routed in a unfortunate way.

Now changing up your board design is most likely an unwanted scenario especially since it works if no debug connection is established.
What you could try though is to lower or increase the debug connection speed.
That way you alter the emitted EM field and with a bit of luck it does not interfere with Wifi anymore or less (if this was the reason for the issue in the first place).

How are you currently connecting to your target device? Through SWD or JTAG?
What connection speed is currently set? Try to increase or decrease it.

Best regards,
Nino

raccoon

Beginner

Date of registration: Nov 29th 2017

Posts: 2

3

Wednesday, November 29th 2017, 4:50pm

Thank you for your prompt response,

I most probably wasted your time.

There must be something wrong with the debug build.

I am connecting to the target's JTAG signal interface.
After trying different adapter speeds (100KHz - 1.5MHz) I was still experiencing the same issue.
I then powered off the JLink and unplugged the corresponding cable from the board, only to find out that the issue persists.

This post has been edited 1 times, last edit by "raccoon" (Nov 29th 2017, 4:54pm)


SEGGER - Nino

Super Moderator

Date of registration: Jan 2nd 2017

Posts: 430

4

Wednesday, November 29th 2017, 5:27pm

Hello,

Ok. Happy bug hunting then.
Are you aware of our runtime data analyzing tool Systemview?
If I read the documentation of your target device correctly it is based on a Cortex-M3 device so it should be compatible.
You can use Systemview while debugging your application and log function calls, events and many more during runtime which can help analyzing a application malfunction especially in time critical environments like WLAN communication.
Should your application be based on our RTOS embOS then you get even more advanced analysis features.

Best regards,
Nino