The monitored data with "spike"

[yang2]

Dear Sir,

When I monitor the data, sometimes the value often accompanied by spikes, such as followed figure.

In my case, I monitor 3 variables that update from ADC registers.

Normally, their values would be around 0.

The signals of ADCvalue[0] and ADC Value[1] appear to be normal.

However ADCValue[2] has some spikes.

When I verify the variables byIDE, the variable does not show these spikes. It always remains around 0.

And I also used a conditional statement to check: if the value is greater than 50 (the maximum spike value is around 260), a counter would increment. However, the counter has always remained at 0, so I believe the actual variable does not have these spikes.

What could be the possible reasons for this?

Best Regards,

[yang2]

Additionally, if I add monitoring of other values, there is a chance that the data will return to normal.

For example, as shown in the image, I added two more monitoring variables, offset[0] and offset[1].

At this point, ADCvalue[2] returned to normal.

[TDK]

The spikes are about 256 off of the real value. It's a int16_t value which is sometimes positive, sometimes negative.

I would guess that whatever is reading the value is doing so one byte at a time rather than both bytes at once, which causes the issue. For example, if you read the first byte when the value is -1, and the second byte when it changes to 1, the reading will be around -256.

How to fix? Not sure. Perhaps change the acquisition mode or add a trigger such that it doesn't probe the value when they're being updated.

[Billy OWEN]

Hi @yang2 

This post has been escalated to the ST Online Support Team for additional assistance.  We'll contact you directly.

Regards,

Billy

[yang2]

Hello TDK, 

I think what you said makes a lot of sense. It might really be caused by the fact that it's transmitted as two separate bytes. Thank you for sharing your opinion.