Strange RTT Behavior After Increasing ..BUFFER_SIZE_UP -- Debug Terminal Repeating Messages

[Rob C]

Environment:
- SES 4.12 on Windows10
- SDK 15.2
- nRF52840 on custom board
- PCA10056 hot-wired for SWD to the custom board for JLINK (sorry Segger, I'm cheap)

I was having trouble losing RTT debug messages (running out of buffer) at boot time, so I thought I'd change "SEGGER_RTT_CONFIG_BUFFER_SIZE_UP" in sdk_config from the default '512' ((0x) 200 if edited using the wizard) to '2048'.

This worked initially, definitely allowed me to capture the entire boot sequence, even if it took awhile to connect the debugger.  However, shortly thereafter, the debug terminal started acting strangely.  I was getting the same message over and over, interspersed with half messages and other characters.  It seemed like the SES RTT terminal was unable to clear the buffer properly.

Having realized that I messed up, I changed "SEGGER_RTT_CONFIG_BUFFER_SIZE_UP" in sdk_config back to the default '512' and reflashed the target.  The problem persisted and was only resolved by performing a full-chip erase using SES Target/Erase All.

Did I miss a step?  What is the proper way to increase the depth of RTT debug when using SES?

Thanks,
Rob

[Hung Bui]

Hi, 

I would suggest to ask this in segger forum as well. 

I'm not sure what cause the problem , but it could be an overflow ? Could you try to set the RTT buffer manually ? You can have a look here and here.