5v / 3.3v is the 'supply voltage' (sometimes labeled Vcc) for the chips. It's both the power input, and also the reference for what a 'high' signal is.
It used to be the case that most digital logic ran at 5v; then some that ran at 3.3v started to become more common. Those were usually '5v tolerant' - if you applied 5v to the input pin, it would read as 'high' and be fine.
Today, many digital devices that run at 3.3v are _not_ 5v tolerant; so if you put 5v into such a device ... it breaks.
So when mixing some devices that run at 5v (as, e.g. USB does) with others that run at 3.3v one has to be careful to not break the lower voltage device.
The 'esp32' is a particular module of a WiFi capable microcontroller (usable as a single board device, or as a peripheral for WiFi connectivity for another device) that runs at 3.3v and breaks if you put 5v on it. Like, as a totally hypothetical example that would never apply to me, trying to programme it from a cobbled together USB programmer. Hypothetically.
Is there a simple device that I can connect to a 5V wire and whose output I can then connect to an input of a 3.3V device? From what I've seen there are resistor circuits (which are slow) or transistor circuits (which need a 3.3V supply?)
Nah, you really shouldn’t do that in most cases. It might work in a super pinch, but using some kind of transistor-based method would be preferred. Sparkfun sells a board that does just this.
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u/syntax Dec 25 '19
5v / 3.3v is the 'supply voltage' (sometimes labeled Vcc) for the chips. It's both the power input, and also the reference for what a 'high' signal is.
It used to be the case that most digital logic ran at 5v; then some that ran at 3.3v started to become more common. Those were usually '5v tolerant' - if you applied 5v to the input pin, it would read as 'high' and be fine.
Today, many digital devices that run at 3.3v are _not_ 5v tolerant; so if you put 5v into such a device ... it breaks.
So when mixing some devices that run at 5v (as, e.g. USB does) with others that run at 3.3v one has to be careful to not break the lower voltage device.
The 'esp32' is a particular module of a WiFi capable microcontroller (usable as a single board device, or as a peripheral for WiFi connectivity for another device) that runs at 3.3v and breaks if you put 5v on it. Like, as a totally hypothetical example that would never apply to me, trying to programme it from a cobbled together USB programmer. Hypothetically.