I am using the Keil uVision5 IDE with the ULINKpro Debug and Trace Adaptor connected to the MCB1700 Evaluation Board. (Target MCU is the NXP LPC1768)
It has been discovered that when in a debug session, analog to digital conversions are affected with additional noise.
This has been revealed by duplicating the ADC result to the DAC and scoping the output.
Does anyone have a solution/suggestion(s) in regards to the additional noise on ADC samples caused by JTAG/Trace during a debug session?
The NXP Application Note AN10974 mentions this problem without offering a solution - does this mean there is no solution?
Do you need to do that kind of debugging in a live environment where the extra noise actually matters? Most noise (unless you have external circuitry with high gain or high impedance) tends to be from the supply voltages, the analog reference voltage and ground - but it's a big step to improve the hardware at a late stage of deployment.
NXP tends to recommend to keep down the CPU load - such as sleeping the core - if you need to really hunt for noise.
The development will be in a dynamic setup where breakpoints cannot be used during run time and trace profiling of ADCs would be of value to monitor system response during operation. However the issue is seen within the MCB1700 Evaluation Board as a standalone setup on a workbench.
I guess trace though the uVision debugger session is just something which won’t work ideally for this application. I will have look at providing this live data though a serial port to PC GUI or LCD instead.
I normally make sure I have a serial channel on production boards so I can look at what happens in a nonintrusive way.
That sounds like a fair idea to adopt. Cheers.