What is the state of I/O pins in reset?

johnabel
Posts: 46
Joined: Sun Mar 26, 2017 5:06 pm

What is the state of I/O pins in reset?

Postby johnabel » Sat May 20, 2017 6:13 am

Hopefully a quick one, I couldn't find clearly in the specs: are all I/O pins in Hi-Z state when in reset?
And is reset pulling the CHIP_PU pin low? (DS says 'it works at minimum power', that doesn't imply a reset, does it? but there isn't any other rest related pin...)

ESP_igrr
Posts: 2067
Joined: Tue Dec 01, 2015 8:37 am

Re: What is the state of I/O pins in reset?

Postby ESP_igrr » Sat May 20, 2017 7:07 am

Please check the "ESP32 Pin List" document (available from Espressif website). In the pin list table, see the two rightmost columns ("at reset", "after reset"). Notes 9 and 10 on the previous page explain the contents of these two columns :)

johnabel
Posts: 46
Joined: Sun Mar 26, 2017 5:06 pm

Re: What is the state of I/O pins in reset?

Postby johnabel » Sat May 20, 2017 7:34 am

I did, but for most of the GPIO those columns are blank. Note 9 says 'During reset, all pins are output-disabled' should I understand they are high-Z or weak pull up/down? And is RESET pulling CHIP_PU low?
Is, for example, GPIO25 an output after reset by default (because of the ie=0 at the last column)?

ESP_igrr
Posts: 2067
Joined: Tue Dec 01, 2015 8:37 am

Re: What is the state of I/O pins in reset?

Postby ESP_igrr » Sat May 20, 2017 10:07 am

If the column is blank for a particular GPIO, then pullup, pulldown, and input are disabled (=hi-Z).
ie=0 means that input is disabled, but that doesn't mean the output is enabled, ie and oe settings are independent. All pins have outputs disabled at and after reset.

johnabel
Posts: 46
Joined: Sun Mar 26, 2017 5:06 pm

Re: What is the state of I/O pins in reset?

Postby johnabel » Sat May 20, 2017 10:51 am

Thanks, that makes sense now.
As input are usually high impedance, it doesn't make much sense to disable them, does it?
That's why I thought disabling them was actually a way of setting them to be outputs.
Anyways, I have now enough info to carry on.

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