Esp-1 CPU Becomes Extremely Hot

[espruino-discuss]

Posted at 2017-02-25 by user74087

Dear All,
I'm having an issue with esp-1 that the CPU becomes extremely hot when put inside an enclosed switch box. Has anyone encountered the same?

Fyi, I have connected VCC, CH_PD, RST pins directly to the 3.3V source. Also there's 10uf capacitor connected parallel to VCC and GND.
Does this wiring has anything to do with the increasing of heat?

Kindly advise.

[espruino-discuss]

Posted at 2017-02-25 by Robin

I have no experience with the ESP-1, but as it isn't mentioned, are current limiting resistors used on the signal lines?

ref: 'maximum current from the espruino pins'
http://forum.espruino.com/conversations/280779/#comment12746768

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Posted at 2017-02-25 by user74087

Thanks Robin.

Actually the gpio pins have not connected to anything. I think RST pin should not connect to the 3.3v source directly. I just experimented and seemingly ok once it is floating.

But is that the real issue?
Is it fine to keep RST pin floating?

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Posted at 2017-02-25 by Robin

Still going over the datasheet myself

There is an internal pull-up of ~10K-40K and needs a limiter during pull-down ~5K internal. A brief pulse to ground shouldn't be an issue, but humans aren't as good chips during a 'quick' pulse. ;-)

I always include the limiter.

Not sure if this is good practice, but I've not had an issue leaving the RST line floating as I confirmed there is an internal pull-up of ~12K. Pulling the RST line hi without a limiter is the same as shorting across the pull-up and current then is limited by the chips internal configuration. Probably will get hot as you have witnessed.

A pull-up of ten+ times the internal, say 100K+ will allow for peace of mind without that much drain on the battery. I see battery drain as the only limiting factor.

Still searching, but these might be helpful:

https://learn.adafruit.com/adafruit-huzzah-esp8266-breakout/pinouts
Link under heading GPIO pins 'Read the full spec sheet'

Good explanation of shorting out reset
https://hallard.me/esp8266-autoreset/

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Posted at 2017-02-25 by @MaBecker

Hi @user74087,

check this ESP-01 sample circuit

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Posted at 2017-02-25 by user74087

Many thanks once again @robin
Your comment helped me to gain a huge insight and I think as you mentioned, and also as per the circuit diagram shared by @MaBecker I should use a pull up resistor and Im sure it will definitely resolve the issue.

Really appreciate for the assistance to resolve this case.

Thanks @MaBecker too for the diagram!

Cheers