ESP32 Ethernet, Wi-Fi & Serial Gateway

[selcuk]

Hello EEVBlog People,

I want to share a recent project of mine with you. This is a design based on ESP32 chip. It is compatible with open source esp-at project. One can easily develop a custom firmware on it as well. Schematics, layout, PCB antenna design and simulations, pin out diagram, part list and much more are available on the link below:

https://github.com/uysan/iot-esp-eth

It is an "Open Source Hardware" developed with "Open Source Software". The software list includes but not limited to KiCAD, OpenEMS and Octave.

The board has ESP32-D0WD-V3 MCU, 16 MB serial flash memory (W25Q128JVSIQ), 10/100 Mbit Ethernet (RTL8201F), 2.4GHz PCB antenna, USB-Serial programming, monitoring and general purpose interface (CH340G), 5V to 3.3V voltage regulator (1117 series), 2.93V supply voltage supervisor (APX811-29UG), protection components and RF shield.

Kind Regards,
Selçuk

[tooki]

Looks nice!

Some questions/comments:
- choosing to use the bare ESP32 IC is a bold move, because that means you have to seek regulatory certification yourself for the radios. (One of the big advantages of using an ESP32 module is that they’re already certified worldwide.)
- why USB mini-B and not USB-C?
- what are the two different Ethernet port versions?
- the datasheet has a typo, the RTC crystal should be 32.768kHz, not 32.758kHz.

[selcuk]

Looks nice!

Some questions/comments:
- choosing to use the bare ESP32 IC is a bold move, because that means you have to seek regulatory certification yourself for the radios. (One of the big advantages of using an ESP32 module is that they’re already certified worldwide.)
- why USB mini-B and not USB-C?
- what are the two different Ethernet port versions?
- the datasheet has a typo, the RTC crystal should be 32.768kHz, not 32.758kHz.

Thank you for your comments and pointing out the error in the datasheet.

I used micro USB since it is cheaper, and I have lots of them at my office. But USB-C is a good idea. I can use it when I make a second revision.

There are two boards with the same functionality in this project. One has components for a temperature range of -40 to +85 °C. That one has a more expensive Ethernet connector. The other board design is for 0 to 70 °C and I used a lower priced connector.

You are right about the certification, but I personally don't prefer to use modules instead of bare MCUs. Even I used it, I would need to get a certification for the whole product. I can say that the ESP32 Ethernet modules on the market are very susceptible to both radiated and transient emissions. The main goal of this design was having a robust ESP32 Ethernet module to use for my projects.

And there is another purpose. After I decided to do an open source design, I wanted to contribute more by not using a module and by doing the PCB antenna design from scratch for this board. ESP32 modules' PCB antennas are not that good, and I thought there was a room for an improvement.

[tooki]

You are right about the certification, but I personally don't prefer to use modules instead of bare MCUs. Even I used it, I would need to get a certification for the whole product.

Huh? I thought the whole point of using the pre-certified modules is to avoid having to get your own certification for the product.

And there is another purpose. After I decided to do an open source design, I wanted to contribute more by not using a module and by doing the PCB antenna design from scratch for this board. ESP32 modules' PCB antennas are not that good, and I thought there was a room for an improvement.

Devil’s advocate: how many others will avoid your design precisely because it’s not certified? And why not just use an ESP32 module with antenna connector (instead of PCB antenna) if one needs better wireless performance? (I use those when I have an all-metal enclosure, so I can attach an external antenna.)

[selcuk]

Unfortunately the module certification is not enough in EMC point of view as well. For example, the ESP32 Wroom module has a certification. If you look at its schematics, there is an RF shield plus a TVS diode at 3.3V supply. With the help of these and a good PCB layout they got a module certification. But I think this is far from enough for your product when you use Wroom module.

I believe this is not a big obstacle preventing people using my design. There are ESD diodes on all IOs, common mode chokes on USB and Ethernet. You may implement most of them even if you use a Wroom module. Except there is a TVS on antenna as well. You may not have it with a Wroom module. So touching the antenna on it by hand is risky. Additionally, the price is different between using a module or a bare MCU.

You are right about the PCB antenna limitation inside a metal enclosure. I can make an updated design having an ufl antenna connector when I have time and budget.

[mianos]

Looks nice. I just got a ETH01-EVO esp32C3 module or the WT-32 ETH01 with S1 chip yesterday, but neither have a USB. I would have got one of yours instead if I knew it was coming out. Always handy having a USB for development and power.  These are both kinda wacky as they have Espressif "wireless-tag" boards, that are ESP32 but pin for pin compatible with the ESP8266 12E modules.

(I am planning on putting a GPS with it to make a local ntp time standard. That's why I wanted an ethernet port myself).

[tooki]

Unfortunately the module certification is not enough in EMC point of view as well. For example, the ESP32 Wroom module has a certification. If you look at its schematics, there is an RF shield plus a TVS diode at 3.3V supply. With the help of these and a good PCB layout they got a module certification. But I think this is far from enough for your product when you use Wroom module.

I believe this is not a big obstacle preventing people using my design. There are ESD diodes on all IOs, common mode chokes on USB and Ethernet. You may implement most of them even if you use a Wroom module. Except there is a TVS on antenna as well. You may not have it with a Wroom module. So touching the antenna on it by hand is risky. Additionally, the price is different between using a module or a bare MCU.

I’m not talking about EMC compliance of the finished appliance, I’m talking about RF certification, like FCC. That’s a whole separate can of worms, and one that is simplified by using a pre certified module. And unlike, say, IEC or CE, the RF certifications are an individual for a bunch of different countries.

For context, here’s Espressif’s certificates for their modules: https://www.espressif.com/en/support/documents/certificates

[selcuk]

I’m not talking about EMC compliance of the finished appliance, I’m talking about RF certification, like FCC. That’s a whole separate can of worms, and one that is simplified by using a pre certified module. And unlike, say, IEC or CE, the RF certifications are an individual for a bunch of different countries.

For context, here’s Espressif’s certificates for their modules: https://www.espressif.com/en/support/documents/certificates

I got it now. Yes, I agree that using a certified module has advantages for RF radiation tests (Wi-Fi, BLE, 2.4GHz etc.) and certification. My previous comments were limited to radiated immunity and emissions, conducted immunity and emissions, and transient immunity tests.

Looks nice. I just got a ETH01-EVO esp32C3 module or the WT-32 ETH01 with S1 chip yesterday, but neither have a USB. I would have got one of yours instead if I knew it was coming out. Always handy having a USB for development and power.  These are both kinda wacky as they have Espressif "wireless-tag" boards, that are ESP32 but pin for pin compatible with the ESP8266 12E modules.

(I am planning on putting a GPS with it to make a local ntp time standard. That's why I wanted an ethernet port myself).

Thanks. I used WT32-ETH01 for some POC work but I didn't know the other one. That WT32-S1 module is different from Espressif own modules. It is okay in general. The only downside is that it has 4MB flash memory. But I think it should be sufficient for your NTP project. And it has a very affordable price tag.