ESP8266 Community Forum

Hi, first post here, hope without breaking forum rules

This is my story:
I haven't found in the industry a cheap and not-third-party-dependant hardware OTP generator, so I'm going to make it, with my own algorithm, let's simply call it "open2fa key".

For this purpose I need:

- A small microcontroller with basic hashing capabilities
- A display
- A Wifi controller to pair token seeds and do ntp sync
- A micro switch to turn on the open2fa key

- A RTC*

The display I'm going to use may be the following:
http://www.buydisplay.com/default/0-91- ... e-on-black

cause it's very small, and I love the format: I want, in the end, to make something that can be attached to my keychain. My inspiration for the design comes from the well-known "RSA SecureID" OTP generator.

My questions are the following, and they're mainly hardware related:

Is the ESP01 suitable for this purpose? I've seen the pinout and if I'm not wrong, I can configure the GPIO as i2C (sorry if I've misunderstood how the thing works, I repeat what I wrote in the subject: total novice here) to feed the display: https://www.letscontrolit.com/forum/viewtopic.php?t=293

In this scenario, with the current algorithm (where timestamp have weight) I need to connect the ESP to a wifi to sync the timestamp, everytime, cause it's off for most of the time.
I can also code a small android app for this purpose, but I actually dislike this design: to "compete" with something like an RSA SecureID the token should be 100% stand-alone.

* Here comes an RTC.
The lifetime of RTCs is awesome, they last years with a small CR battery. What discouraged me is the cost. For a small i2c RTC I've seen only 15$ stuff (https://www.sparkfun.com/products/12708). Nope.
The second question is, so, are you aware of a very-very-cheap and small sized RTC out there?

I can think about a timestamp-less algo with deterministic generation of tokens from a shared seed and server-side error correction when the entities go unsynched (i.e., you generate tons of OTPs without using them), but looks like a messy patchwork, I would love to use the timestamp.

Finally, the power consumption.
With two paired CR batteries I can get up to 180mAh, and this table from espressif gives me hope:


Given the OTP is by design used for a very short time, looks like the whole thing can work, but what got my attention is the "deep sleep" mode. The third question is so about this mode. Can an ESP in deep-sleep mode be able to act as a RTC, once in sync ?

So, brainstorming is open, I hope this will drive me into something sensible, and a so github repo of the project will follow, thanks for your help

Ok, I've found a couple of interesting posts about what I am willing to do:

This PDF from Espressif about sleeps mode: http://www.espressif.com/sites/default/ ... s_en_0.pdf answer my third question: while in deep-sleep mode, the RTC of the ESP8266 is up, sounds like a way to go..

This fancy hack to allow ESP01 to wake up from deep sleep mode: http://hackaday.com/2015/02/08/hack-all ... eep-sleep/

What I need to understand is if I really need this, cause I don't need to wake up the ESP programmatically, but from a button. So, mmh ? Is this hack needed to wake up the ESP from RTC ?

If I put an ESP01 into deep sleep mode, do I have to use the GPIO to wake it up, or ... ? Still a little bit confused, need to study more how the thing works and how to turn on an ESP01 while in DS mode.

Finally, I've understand that I need, to begin, to flash the factory AT firmware with the NodeMCU one, that allows me to program the ESP using the Arduino IDE. Looking forward?

The ESP CPU runs up 160 MHz so do you need a separate microcontroller for hashing? I would not use AT command firmware and use Arduino firmware instead. An ESP-01 might work but I have not used one.

Check out the Adafruit Feather ESP8266 CPU board with lithium battery charger. Stack an RTC board on the ESP8266 CPU board. There are three RTC boards to choose from depending on how accurate the RTC needs to be. Then stack an OLED display board on the RTC board. This will be large and expensive but it gives an idea of what is possible.

There is no need to use Adafruit stackable boards at all since other vendors also sell ESP-12, RTC, and OLED breakout boards. For example, a small $5 RTC breakout.

https://www.adafruit.com/products/3295

Since the project needs to wake up from a button push, the simplest solution is to use the RESET button included on most ESP breakout boards. Or hook up another button in parallel with the reset button on the board. Or just connect a normally-open button between the ESP8266 RESET and GND.

Another option is to use the CH_PD pin. Search this forum for wake up using CH_PD.