I was wondering if someone knows a way to convert a ESP8266 to non-WiFi. I.e. have it connected through Ethernet, preferably with PoE possibility.

Reason for asking: My plan is to have sensors in a locker which is not a wifi-friendly environment. I want to monitor humidity and temperature in particular. I have a lot of ESP8266 units and like the firmware ESPeasy, thus wanting to stick to that platform.

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    Can you explain why you are asking? To make your question easier to answer well, you need to explain your constraints. What makes this hardware preferable to a MCU board which already supports ethernet? How is your question different to 'how can I convert a MCU which supports ethernet to operate with PoE'. – Sean Houlihane Feb 2 '17 at 10:25
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    You may spend more time struggling to get Ethernet working that you would switching to a different MCU. – Dmitry Grigoryev Feb 2 '17 at 14:56
  • An alternative, would be to use ethernet cable for power and serial TX/RX... instead of using it for actual TCP or UDP traffic. You could have all your ESP's wired up to a "hub" of your making which reads/sends over the ethernet using serial, and power can be provided over another wire pair in the same ethernet cord. You may need some protection on the ESP side depending on the length of your cable run and how many volts you need to send down it. I believe PoE uses 48v. – SnakeDoc Feb 2 '17 at 16:33
  • What MCU with embedded Ethernet controller you have in mind ? – Pascal Kiliam Aug 3 at 6:13
up vote 10 down vote accepted

The simplest solution is to add an external ethernet interface driven over SPI, as used in this example.

It's also possible to bit-bang the ethernet interface directly, as decsribed in this article, Ethernet Controller Discovered in the ESP8266. Performance might not be as good as with a dedicated interface though.

Neither of these include Power over Ethernet, and the latter will probably not leave you with very much spare compute resource (although your application many not care).

If you're interested specifically in PoE, this Teensy forum thread discusses building a shield for a board. Although the base board is in production, it doesn't look like the ethernet shield is yet.

The ESP8266 was not designed with an Ethernet MAC, but this should not stop you. However, as Sean has said, it imposes a set of pretty severe restrictions on you.

You say that you wish to stay with the ESP8266 platform, but if your project cannot deal with the measly data rates provided by using an ENC28J60-style chip, or bit-banging Ethernet, then there is an alternative. The ESP32 has a 10/100 Mb/s Ethernet MAC that only requires a PHY, magnetics, and an RJ45 connector, and the ESP32 modules are just as cheap (if not cheaper) than the ESP8266 ones.

The unfortunate downside to this approach is that it does not appear that many ESP32 shields have made it to market yet.

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