Connecting the Plantower 5003 dust sensor to the ESP8266 12E via serial - technical issues

Hi I want to serialise a Plantower 5003 dust sensor to an ESP8266 12E and I'm having a problem because it works a bit weird and incomprehensible to me.
1) The 12E has one and a half serials (I thought it had two) Serial = RXTX on Pins GPIO3 and 1; and Serial1 = samTX on GPIO2
RX should be on GPIO0 but there is a FLASH input there
2) on 12E there are also additional Serial - RXTX outputs on GPIO13 and 15 pins to which standard outputs can be transferred with Serial.swap() command

And now what happens:
(a) I connect the sensor to the standard Serial outputs GPIO3 and 1 - the sensor works and the debug on Serial also works (admittedly, it seems to me that I should see communication with the dust sensor in this terminal from Serial - and I don't see it - but it doesn't matter)
Unfortunately, such connection blocks me from uploading a new program - simply Arduino doesn't detect the connected board in flashing mode
b) OK, let's do Serial.swap() and connect to GPIO13 and 15 outputs. OK works - but it also switches debug and debug information is not shown on the computer terminal.
(c) In playing with these, I noticed one inexplicable thing.
Normal configuration without Serial.swap()
- I connect the sensor to GPIO13 and 15 - doesn't work - OK understandable because communication is on standard GPIO3 and 1
- switch "on the fly" the sensor to GPIO3 and 1 - works - OK
- switch "on the fly" the sensor to GPIO13 and 15 - WORKS although it should not!
- board reset
- sensor does not work (OK)
What such a strange thing happens when switching on the fly from GPIO3 and 1 to GPIO13 and 15 - looks like both outputs work!!! I don't understand.

How do I get around this problem of using serial to communicate with devices and debugging at the same time - the device blocks me from changing the program - why? I can at least add some software serial, but I would like to understand what is happening.

And a quick question from 12E - on the pine Vin shouldn't +5v from USB be derived? Is it derived somewhere because I don't see it (I wanted to power the sensor from USB)

jurek.parus wrote:

a) I'm connecting the sensor to standard Serial GPIO3 and 1 outputs - the sensor is working and debug on Serial is working too (admittedly I think I should see communication with the dust sensor in this Serial terminal - and I don't - but it doesn't matter).
Unfortunately such a connection blocks me from uploading a new program - simply Arduino doesn't detect the connected board in flashing mode

Quite understandable - you are trying to use UART0 to communicate with two different devices.

jurek.parus wrote:

What's so weird about switching on the fly from GPIO3 and 1 to GPIO13 and 15 - looks like both outputs are working!!! I don't understand.

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Not quite. There are still buffers for UART0 that can cause this transient effect when switching Serial - swap() does not clear these buffers.

In general, if you want to use UART0 (regardless on which pins) to output diagnostic data, you should unfortunately use software Serial to handle the sensor.

khoam wrote:

jurek.parus wrote:
What's so strange about switching on the fly from GPIO3 and 1 to GPIO13 and 15 - looks like both outputs are working!!!! I don't understand.
Not really. There are still buffers for UART0 that can cause such a transient effect when switching Serial - swap() does not clear these buffers.

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I do not use Serial.swap in this case. The effect is not transient. I am not reading data from the buffer because the sensor is reading the correct data. After a reboot it returns to normal. Strange.
I will connect SoftSerial as you advise.

jurek.parus wrote:

And a quick question from 12E - on the pine Vin shouldn't +5v from USB be derived? Is it led out somewhere because I don't see it (I wanted to power the sensor from USB)

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Which specific board are you referring to with the ESP12-E module? NodeMCU? In which version?

Here was a similar topic: https://www.elektroda.pl/rtvforum/topic3750706.html

khoam wrote:

Here was a similar topic:

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Yes, it's a similar issue - I need to find that diode and bridge it.