Document high tx power can cause issues

[devyte]

Basic Infos

• This issue complies with the issue POLICY doc.
• I have read the documentation at readthedocs and the issue is not addressed there.
• I have tested that the issue is present in current master branch (aka latest git).
• I have searched the issue tracker for a similar issue.
• If there is a stack dump, I have decoded it.
• I have filled out all fields below.

Platform

• Hardware: All
• Core Version: All
• Development Env: All
• Operating System: All

Settings in IDE

• Module: Wemos D1 mini Pro

Problem Description

Issue #6366 turned out to be high tx power causing weird behavior. Lowering tx power achieved stability.

This issue is meant to track documenting that.

[earlephilhower]

This sounds like more a question for the board maker than something on Arduino related. I think #6366 might just have gotten unlucky with either power supply, board builders, or a wonky lot of silicon. I've not seen it repro'd outside of his report.

[ChocolateFrogsNuts]

I think it was more of a design choice by the board builders - smaller board vs higher TX power.
Switching to an external antenna also resolved the issue - ie moving the antenna further from the chip allowed it to operate at full TX power with no issues.

I think it's worth documenting as this won't be the last tiny board with an ESP chip on it - there are at least 3 variants/versions of this same sized board from the same manufacturer.

Mind you given there are several issues on esp8266.com with weird behaviour similar to what I saw it probably should be raised there too. Might help a few people out.

[devyte]

There is also the ESP-7. Old, but I've seen a few around.
In any case, my intent is to have the symptoms captured and workaround described. There are a lot of whacky cheapo boards out there, I wouldn't be surprised that some of the connectivity issues we've seen reported here could have been addressed by reducing Tx power. Also, the suggestion came from users, which makes me think it's a bit of wisdom already floating around in the community => worth solidifying into text.

[JAndrassy]

@devyte, it was my original idea. It is not floating around. I am not an expert on esp8266, but close to be one :-) I spent many hours reading the docs and playing with the esp8266.

[devyte]

Even better, from a user's practical experience.
@JAndrassy since it was your wisdom, would you like to do the writeup?

[JAndrassy]

Even better, from a user's practical experience.
@JAndrassy since it was your wisdom, would you like to do the writeup?

I will try to reproduce it first. I think I encountered this problem in past more then once with different boards/modules but I didn't investigate it then. And the relation of this problem to calibration and the RF settings area initialization.

[ChocolateFrogsNuts]

Further info available... see my post
#6366 (comment)

Basically it appears to be a cheap flash chip issue and dropping the flash frequency to 26mhz is likely the preferred fix.

[readmodifywrite]

Note that the default tx power is set to maximum (20.5 dbm), however, 802.11n on the 8266 is only spec'd to 17 dbm.

[ChocolateFrogsNuts]

@readmodifywrite interesting point, and unsurprisingly close to the figure my testing pointed to as being stable :-)

[devyte]

@JAndrassy said:

I will try to reproduce it

ping?

[JAndrassy]

I didn't have time first, but now I go over problems I had with esp8266 in last two years and investigate them with RF TX power as one of potential causes.
Yesterday I found a bug in WiFiLink firmware sketch which made the firmware behave strange since arduino.org coders created it. And it was a simple char array overflow in SoftAP SSID creation. So no WiFi problem.
Today Robotdyn D1 R2 with external antenna option is on schedule.