IO0 and IO2 pullup / pulldown resistors

hakkig
Posts: 9
Joined: Fri Dec 01, 2017 9:56 am

IO0 and IO2 pullup / pulldown resistors

Postby hakkig » Fri Dec 15, 2017 9:32 am

Hi,

On Espressif's devkit IO0 and IO2 pullup / pulldown resistors are not present.
When designing my own board with WROOM32 module can I omit them entirely?
Another question is about the capacitor from the EN pin to ground. On some designs it is not present.
I suppose it is to introduce a delay to EN going high on power up. How essential is it?

Thanks in advance, cheers

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krzychb
Posts: 204
Joined: Sat Oct 01, 2016 9:05 am
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Re: IO0 and IO2 pullup / pulldown resistors

Postby krzychb » Fri Dec 15, 2017 10:39 am

Hi hakkig,
hakkig wrote:On Espressif's devkit IO0 and IO2 pullup / pulldown resistors are not present.
When designing my own board with WROOM32 module can I omit them entirely?
Yes, ref: Hardware Design Guidelines:

Each strapping pin is connected with its internal pull-up/pull-down during the chip reset. Consequently, if a strapping
pin is unconnected or the connected external circuit is high-impendence, the internal weak pull-up/pull-down
will determine the default input level of the strapping pins.

hakkig wrote:Another question is about the capacitor from the EN pin to ground. On some designs it is not present.
I suppose it is to introduce a delay to EN going high on power up. How essential is it?
Yes, it is essential ref: Hardware Design Guidelines:

ESP32 uses a 3.3V system power supply. The chip should be activated after the power rails have stabilized. This
is achieved by delaying the activation of CHIP_PU (Pin9) by time T after the 3.3V rails have been brought up. The
recommended delay time (T) is given by the parameter of the RC circuit. For reference design, please refer to
Figure ESP-WROOM-32 Peripheral Schematics in the ESP-WROOM-32 Datasheet. (check also a notice inside)

hakkig
Posts: 9
Joined: Fri Dec 01, 2017 9:56 am

Re: IO0 and IO2 pullup / pulldown resistors

Postby hakkig » Fri Dec 15, 2017 10:47 am

Thanks a lot, cheers

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