ESP8266 Community Forum

- Fri Aug 14, 2015 4:32 pm #26006

this will short circuit the output from the other devices ...

Ehh? Care to elaborate . It does not make much sense to me.What other devices are you talking about and where did you manufacture them from?

Get you modules here:

https://www.banggood.com/custlink/KvGGhGF4wG

- Fri Aug 14, 2015 4:38 pm #26008 Those diodes are there only for ESD protection, there are derived the current from the inputs to the VDD pin, so with any above voltage, the current flow will derive, protecting the input pin. But this derived current can destroy the source if it becomes permanent current instead of only a spikes. In long terms, either the output of the connected device will suffer and blow up, or the diode itself if current is too strong, therefore if the diode blows up, no more protection is available. So, that why the 3.6V limit is prevailing for long duration ...

- Fri Aug 14, 2015 4:54 pm #26013 Also the datasheet only states that the pins are supposed to be protected against overvoltage. It does not claim anywhere, that the I/O pins will operate reliably at input voltages above 3.6V (at least I cannot find anything suggesting that).
So if you apply more than 3.6V to a pin, the value you are reading may be random.

Last edited by lethe on Fri Aug 14, 2015 7:01 pm, edited 1 time in total.

- Fri Aug 14, 2015 5:18 pm #26019

So if you apply more than 3.6V to a pin, the value you are reading may be random.

You're right ! This remember me the "common mode" in voltage comparators : most comparator has a common mode voltage of VDD - 1.5V, so having a VDD of 5V, this bring the voltage range that can be compared from 0 to 3.5V, any voltage above will produce random comparison. But this is a completely different subject ...

Last edited by martinayotte on Fri Aug 14, 2015 8:47 pm, edited 1 time in total.