AVR - ATMEGA328p ADC keeps returning 1023

Question

We have developed an Atmega328p based Kit. We want to read some analog sensor values in the application. But analog readings always returns 1023. Even If we connect GND pin with analog pin, it gives 1023.

Here the schematic diagram has been attached.

We tried with both Arduino analogRead() function and microc function adc_Read(). Both adc reading always returns 1023.

We have also followed these Q&As below:

Q&A StackExchange

Q&A StackOverflow

Q&A AvrFreak

But no luck yet.

Is there any bugs in our schematic?

Your suggestions and helps are appreciated.

Thanks in advance.

Answer 1

As FakeMoustache mentioned, the problem was in connecting AREF directly to GND. After we connect the AREF to GND via 1uF decoupling capacitor, it works fine.