[solved] Reset: is a 10K resistor required ?

nounours18200
Posts: 7
Joined: Fri Nov 15, 2019 4:57 pm

[solved] Reset: is a 10K resistor required ?

Postby nounours18200 » Wed Feb 19, 2020 1:05 pm

Hi,

I use an ESP32 Pinboard and on this page:
https://www.14core.com/wiring-and-flash ... -ttl-uart/

it is shown that there is a 10K resistor between the +3.3V power supply and the RESET button.

The RESET button can be soldered on the pinboard, but this 10K is not present on the Pinboard, and if I solder one out of the piboard, it becomes useless to have the reset button on the pinboard.

Is this 10K resistor required ? if the reset simply consists to pull down the EN pin to Ground, I do not see why we need this resistor ?

Thank you
Last edited by nounours18200 on Thu Feb 20, 2020 7:57 pm, edited 1 time in total.

User avatar
ESP_krzychb
Posts: 272
Joined: Sat Oct 01, 2016 9:05 am
Contact:

Re: Reset: is a 10K resistor required ?

Postby ESP_krzychb » Wed Feb 19, 2020 2:20 pm

nounours18200 wrote:
Wed Feb 19, 2020 1:05 pm
Is this 10K resistor required ? if the reset simply consists to pull down the EN pin to Ground, I do not see why we need this resistor ?
Hi nounours18200,

You add a resistor because a floating pin is subject to electrical noise which could cause random resets.

nounours18200
Posts: 7
Joined: Fri Nov 15, 2019 4:57 pm

Re: Reset: is a 10K resistor required ?

Postby nounours18200 » Wed Feb 19, 2020 2:55 pm

because a floating pin is subject to electrical noise which could cause random resets
It is exactly what I meant, and I supposed that when RESET is engaged, the value of R is so high (10K) that there is no risk of short circuit: I=U/R = 5/10000 = 0.5mA

By the way, do I have to maintain RESET engaged all along the flashing process, or just at the begining ??

mikemoy
Posts: 447
Joined: Fri Jan 12, 2018 9:10 pm

Re: Reset: is a 10K resistor required ?

Postby mikemoy » Wed Feb 19, 2020 4:25 pm

By the way, do I have to maintain RESET engaged all along the flashing process, or just at the begining ??
If its held in reset, how could you flash it?

https://github.com/espressif/esptool/wi ... -Selection

nounours18200
Posts: 7
Joined: Fri Nov 15, 2019 4:57 pm

Re: Reset: is a 10K resistor required ?

Postby nounours18200 » Wed Feb 19, 2020 4:57 pm

Sorry, it was stupid... (I made a confusion between Reset and I00 connected to ground...)

Thank you for your replies,
Michel

mikemoy
Posts: 447
Joined: Fri Jan 12, 2018 9:10 pm

Re: Reset: is a 10K resistor required ?

Postby mikemoy » Wed Feb 19, 2020 7:46 pm

No sweat.... To answer your question is yes you can keep it low during flashing.

nounours18200
Posts: 7
Joined: Fri Nov 15, 2019 4:57 pm

Re: Reset: is a 10K resistor required ?

Postby nounours18200 » Thu Feb 20, 2020 8:20 am

you can keep it low during flashing
Do I can or do I must: I mean is a temporary pull down to GND is enough to start the flashing process of the firmware a few seconds later ?

All the articles that I have read shows a I00 permanently to GND all along the flashing process....


Thank you,

mikemoy
Posts: 447
Joined: Fri Jan 12, 2018 9:10 pm

Re: Reset: is a 10K resistor required ?

Postby mikemoy » Thu Feb 20, 2020 6:37 pm

Either way is ok.
Whats is happening is when it comes out of reset, its checks GPIO0 state. If high then it boots up normally. If low then it goes into flashing mode.

So, just as long as GPIO0 is low BEFORE reset (EN PIN) returns high your in flashing mode.

nounours18200
Posts: 7
Joined: Fri Nov 15, 2019 4:57 pm

Re: Reset: is a 10K resistor required ?

Postby nounours18200 » Thu Feb 20, 2020 7:56 pm

Thank you very much Mikeymoy: it is cristal clear ! :D

Who is online

Users browsing this forum: Bing [Bot], Google [Bot] and 7 guests