WIFIO is a dual Arduino WIFI module (ESP8266+ATMEGA328P) FCC approve-able with transferable licence. Can use the 328P for I/O expansion also...

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By dkinzer
#27660 I've been doing some research on various techniques for automatically putting the ESP8266 into download mode. One that I've seen labeled "wifio" has a PNP transistor to pull the GPIO0 line low when the RxD line goes low. The downloader sends a break on the serial line to hold GPIO0 low while the ESP8266 is starting up after rset.

It occurred to me while pondering that circuit that a diode would serve in place of the transistor and base resistor. I tried it and it seems to work perfectly. The circuit that I tested is shown below, the pullup resistors are actually on the ESP8266 board.
wifio_reset.jpg
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By dkinzer
#28628
alon24 wrote:can you please give values, and show how to use this?
As I mentioned, the pullups are probably already on your ESP8266. If not, they're not particularly critical so 10K or so should work. The diode that I used was a 1N914 but any "small signal" silicon diode with a reasonable forward voltage should work. A Schottky diode (e.g. BAT42) would be even better since they have lower forward voltages. The capacitor that I used was a 100nF ceramic but I've seen others use a 1uF capacitor.

In order to use this automatic reset circuit, you'll need a downloader application that supports it. I'm pretty sure that esptool.py does not support any automatic reset protocols but I could be wrong. The esptool.exe downloader (available on github and provided with the ESP8266 Arduino setup) does support several reset protocols. My esp_tool application (also on github) supports several reset protocols as well. (I do need to update the github repository with the latest code that was tested with the diode circuit.)
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By jumpjack
#73009 What about a self-reset circuitry which does not require PC connection? I think it would be very useful to prevent well knwon unpredictable resets/locks of the ESP8266: just self-reset every 24h and you're fine!
But, how to implement it?
I tried by connecting RST to D8 and putting D8 to GND programmatically... but of course it didn't work: who will put RST high then?!? :lol:
Maybe a small&cheap external circuit could be built? A solid state relay + capacitor + transistor would do the trick?
As long as the ESP8266 is on, the capacitor is charged; as soon as D8 is put high, relay is triggered and RST put to GND... then in "some manner" which I yet have to figure out, the capacitor brings it back to 3.3V...
Any help?