I have been trying to use the built-in GPIO pins to read an analogue value (thermistor voltage divider and voltage drop on diode from 3.3V). Both of these should be very clean signals.
However, the readings I get are extremely noisy. For example, here you can see the readings done in Python (1 second update):
I can also see the value jumping if I use the WizConfig tool to read the GPIOs
I have checked the actual value with an oscilloscope and no noise is present.
I have used a dc-dc to converter to 3.3V and a linear regulator from 5V USB with the same results.
This happens with the two WIZ750SR modules I have.
Hello. How many ADC channels did you use together? Did you only use one?
I tried several configurations with similar results.
I also noticed strange things. GPIO A seems to have a weak pull up to 3.3V enabled by default in analogue mode. It pulls the analogue value at its pins to a higher value.
Also, GPIO D in digital output mode alternates between GND and 3.3V at about 1-second intervals. This happens in several modules.
You mean ADC used only one channel…? It was often a problem with more than one ADC channel. However, I didn’t see any issues with ADC 1 Channel. Even when we tested it, it didn’t matter when we activated one ADC.I will test it with the module and share the results with you. Thank you.
The graph I showed was taken on GPIO B.
For my application, I would like to use 3 analogue inputs and one Digital Output. The issue is that it seems that GPIO A has a pull up to 3.3V in analogue mode (and lots of noise) and GPIO D is alternating between GND and 3.3V at about 1-second intervals so it seems it is being used by some other function in code… GPIO B and C are just noisy.
There seems to be a problem.
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