esp8266：uart wifi Unable to work together

[maike maker]

esp8266 TX connect pico RX，code only uart，pico can receive messages

add wifi ,pico unable to receive messages

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[John Maloney]

Thank you for reporting this. I will investigate.

[John Maloney]

Sorry for the delay.

I could not reproduce this problem on my NodeMCU ESP8266 board.

To debug, try removing the "serial write" block from the receive loop. If that works, then it means that simply having the serial port open isn't the problem. If it fails, then it could be that there is an electrical issue. The 8266 serial TX pin is pin 4. If there is a low-resistance path from that pin to power or ground, then opening the serial port could be causing a power issue.

If failures occur only when the "serial write" block is included in the loop, that could also be an electrical problem. On my board, pin 4 is connected to the user LED through a resistor. The LED blinks during serial write, but the WiFi continues to run. But I can imagine a similar circuit disrupting the power supply enough to disrupt WiFI reception or even cause a processor reset.

[maike maker]

Thank you for your suggestion. I will provide feedback after testing according to your method.

[Turgut Guneysu]

Hi Everyone,

Just to provide another point of view, I also tested the provided code on a WEMOS8266 and PICO-W.
A few issues with the provided scripts:

• It has no Serial Read and display; only WIFI Read and Serial Write
• ESP8266 cannot read SERIAL. So, I don’t understand what the Serial write is used for ?
  Seems like it was meant to be a WIFI Send, to create a back and forth message loop to test.
• The actual problem is with Serial Open: it needs to happen after WIFI Connection.

>>> John: you may have to examine the Serial open after WIFI issue.

Here is pair of scripts that demos back and forth message exchange using WIFI and SERIAL. Just load each to corresponding microcontroller and run:

• ESP8266 can only write Serial; so it receives Radio WIFI messages and writes them to Serial
• PICO-W does both; reads Serial and reads & writes Radio WIFI message

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[John Maloney]

Thank you for testing, Turgut.

I'm not seeing any issues with this on my Wemos D1 mini board. In my testing, it did not matter if the serial port was opened before or after connecting to WiFI.

Here's my code on the Wemos:

I also tried opening the serial port first:

To test, I ran the following script on an ESP32:

With the second scripting running on the ESP32, I see a constant stream of incoming wifi strings with different timestamps.

[Turgut Guneysu]

OK, I am puzzled! Now it works with Serial Open either before or after.

Gremlins in my system again… Sorry!

[John Maloney]

No worries! There are so many variables, including the fact that WiFi connect is not totally reliable...

[John Maloney]

Since I cannot reproduce this issue I'm going to mark it as resolved. Feel free to mad additional comments here.