ESP8266 Community Forum

- Tue Mar 10, 2020 6:36 am #86012 I am building a custom board for an ESP-12F. The board will allow for the ESP to reset on an external button or PIR, and run an LED, and provide hooks for flashing. It is powered via a battery and low leakage is desired.

This forum and the datasheets have provided great information. Question: should GPIO2 and CH_PD be connected directly to VCC or connected via resistor? Any others?

I don't plan to use RTS/CTS during flashing, but the FTDI’s have it and maybe a future project will use it; so I put in the hooks for it. But I am confused because IO15 is supposed to be held low for flashing and running. Is it enough to have a jumper that allows IO15 connection to GND or FTDI-CTS?

Here is a schematic and table reviewing the pin-out for proper management during flashing, booting, and running.
Please let me know if you see any glaring errors.






Link to pics if needed.
https://photos.app.goo.gl/Lz6rhJVxCdSrLK6s7

Thanks!

- Tue Mar 10, 2020 9:07 pm #86019 I normally use a 10K pull down resistor to create the required low on GPIO15. This way I can still use it as an output after the module has started up.

A good write up of the pin behaviour can be found at https://www.mjt.me.uk/posts/esp8266-gpio-deep-sleep-and-reset/.

- Wed Mar 11, 2020 12:58 pm #86027 The issue with this circuit is the thing that happens when switch S1 is shut. This makes a direct electrical association among Vcc and GND. As such, it will short out the circuit. On the off chance that you are fortunate, it will simply prevent your whole framework from working. In the event that you are unfortunate, it will consume the wires!

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- Sun Apr 12, 2020 6:10 am #86466 Never tie GPIO's to either Vcc or GND directly. If the GPIO gets programmed as output, even for a short moment (maybe during booting), it will sink/source far too much current and the port will blow.

So always use a resistor. I generally use 10 kOhm, but 22 kOhm seems to work really well to. If the GPIO pin is an output for some time, it will only draw 330 microA.