WIZ750SR Noise on analog GPIOS

Question

Hello All. 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. Any thoughts? Thank You

Alan · Answer

Hello. How many ADC channels did you use together? Did you only use one?

Alan · Answer

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.

Ironic · Answer

Alan: 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. Dear Alan 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. Regards

Alan · Answer

There seems to be a problem. Please contact us by e-mail below. Alan@wiznet.io