FDC2212: FDC2212 acquisition sensor signal background error

Hello, 

For liquid level sensing, we typically recommend the Capacitive Sensing: Out-of-Phase Liquid Level Technique since it is the most robust to external noise such as touching the tank. 

As for the measurement not fully returning to the normal value I have a couple questions that will help determine what is occurring. 

• Can you view the sensor oscillation on an oscilloscope for both cases (before and after touch) and compare the amplitude and frequency of the sensor? 
• Before you wakeup the FDC in your code, can you perform a read of the config register and let me know what the value is? 

Thank you, 

Justin Beigel

1. When there is no touch action, the output value always keeps a small change, when there is touch, the output value becomes low, when the hand leaves the sensor, the output value soon returns to the output value, some sensors, the output value is far lower than the value before rough grinding;Only through the chip reset, restore to the value before touch;

2. Does not use low power consumption or sleep mode, has been converting data 2 times per second;

Hello, 

Can you provide oscilloscope screenshots or the sensor amplitude and frequency measurements on these cases? 

Thank you, 

Justin Beigel

May I ask which pin amplitude and frequency?

Hello, 

It would be pin IN0A or IN0B. You don't have to look at both but can if you want to see both halves of the sensor waveform. 

Best Regards, 

Justin Beigel

normal

Abnormal situation

Hello, 

I would start by decreasing the Idrive setting so the amplitude is smaller, but still above 1.2V. 

Also, I can't quite tell from your code if this is the case or not, but make sure that the reserved bits of the Config register (bits 10 and 12) are written with 1 when you write that register: 

Let me know if this helps the issue. 

Best Regards, 

Justin Beigel