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Electronics => Beginners => Topic started by: fossil on January 19, 2019, 02:14:53 am

Title: ESP8266 Custom Board
Post by: fossil on January 19, 2019, 02:14:53 am
I have been watching this wonderful forum for many years. I could say, this forum has given me courage to consider the following project.

I am looking forward to build a standalone custom ESP8266 board based on ESP-WROOM. This exercise is purely for academic purpose. I want to learn how to use a wireless chip instead of module. If you are wondering why ESP8266, I have been given few dozen ESP8266EX, purchased as samples from Espressif, by a friend of mine.

The spec I am considering
I want this board to work with any power source as long as voltage is less than 14V. I am aware of challenges of designing DC/DC converter. I intend to use the PCB design from TI WEBENCH. Further, I have read the ESP8266 hardware design guidelines document. The board will be 4 layers as suggested in hardware guidelines.

I have soldering station, hot-air, 50MHz oscilloscope. I am looking forward to build a toaster reflow oven soon.

I am wondering what problems are in store for me?
Title: Re: ESP8266 Custom Board
Post by: JoeO on January 19, 2019, 03:52:34 am
Go to youtube and search "reflow toaster oven".

There are many videos there that can give you the information that you want.
Title: Re: ESP8266 Custom Board
Post by: fossil on January 19, 2019, 09:51:46 am
Quote from: JoeO on January 19, 2019, 03:52:34 am
Go to youtube and search "reflow toaster oven".

There are many videos there that can give you the information that you want.

I do have a controller board for toaster oven. I am planning to build next weekend.

I am looking for advice on building standalone esp8266 board.
Title: Re: ESP8266 Custom Board
Post by: 128ITSH on January 20, 2019, 04:38:58 pm
With what part of the board are you struggling? What you want to do is very achievable. Like you said the main challenge I see here is designing the power supply circuitry as efficient as possible. The 8MB flash probably has simple connections to the chip. A thing worth to consider is protecting the Wi-Fi Antenna traces from the switching noise of the power supply. Could be done by putting each on a different side of the board and even using metals to enclose the switching supply. Not so sure about this so look for it online.
Title: Re: ESP8266 Custom Board
Post by: fossil on January 21, 2019, 02:27:51 am
Quote from: 128ITSH on January 20, 2019, 04:38:58 pm
With what part of the board are you struggling?
I can't say I am struggling. As of now, I am almost done with schematic. I am trying to find out if there any other things to watch out for.

Quote from: 128ITSH on January 20, 2019, 04:38:58 pm
The 8MB flash probably has simple connections to the chip. A thing worth to consider is protecting the Wi-Fi Antenna traces from the switching noise of the power supply. Could be done by putting each on a different side of the board and even using metals to enclose the switching supply. Not so sure about this so look for it online.
I am considering to shield the power supply.  Probably, I will also try to shield the wireless chip and analog section as seen in other modules
Title: Re: ESP8266 Custom Board
Post by: LukeW on January 25, 2019, 03:01:40 am
Remember your Vdd needs to be 3.3v not 5V.

Make sure the power supply is clean and stable, can supply appropriate current, and use good decoupling.

Follow the reference designs - hard to go wrong.

You need to pay attention to what flash chip you use - DIO, QIO, double check the pinout and flash speed and page size etc - write to the flash accordingly. Settings that don’t match will cause programming failure.

And then there’s the antenna. Make it a 50 ohm CPWG line with usual impedance design practices.

Put a pi network (0402 footprints) before the antenna to allow matching, and a “T junction” to a uFL connector or similar, with a 0 ohm resistor. This allows you to connect up a VNA and measure s11, and tune up the antenna and matching network for best results.

A lot of cheap modules just seem to use 5.6pF for the series capacitor and NP the two shunt inductors which seems to work ok for typical meandered little 2.4GHz antennas.
Title: Re: ESP8266 Custom Board
Post by: fossil on January 25, 2019, 03:39:54 am
Quote from: LukeW on January 25, 2019, 03:01:40 am
Remember your Vdd needs to be 3.3v not 5V.

Make sure the power supply is clean and stable, can supply appropriate current, and use good decoupling.
The plan is to use an LDO to power ESP8266.

Quote from: LukeW on January 25, 2019, 03:01:40 am
You need to pay attention to what flash chip you use - DIO, QIO, double check the pinout and flash speed and page size etc - write to the flash accordingly. Settings that don’t match will cause programming failure.
I will pay attention. The WROOM-02 reference design uses "WP" and "HOLD" to interface with flash. I suppose I need to make sure I select the flash which has "WP" and "Hold" pins.

Quote from: LukeW on January 25, 2019, 03:01:40 am
And then there’s the antenna. Make it a 50 ohm CPWG line with usual impedance design practices.

Put a pi network (0402 footprints) before the antenna to allow matching, and a “T junction” to a uFL connector or similar, with a 0 ohm resistor. This allows you to connect up a VNA and measure s11, and tune up the antenna and matching network for best results.

A lot of cheap modules just seem to use 5.6pF for the series capacitor and NP the two shunt inductors which seems to work ok for typical meandered little 2.4GHz antennas.
I will follow above guidelines. I don't want to compromise on performance without going overboard.

Thank you very much for all the help.