Wemos D1 mini v3

[Kotik82]

Had previously a Wemos D1 mini pro with 16mb flash and everything was working fine (using the spiffs) but as i use that board for other projects i ordered a Wemos D1 mini v3 and a SD card shield for it.

After compiling and uploading to the new board i was able to connect and configure wifi but connecting it to the printer simply doesn't work, the device connects properly to the wifi network but it seems to be unable to communicate with the printer over UART. I checked and triple check my wiring and everything seems to be ok.

If i replace the D1 mini V3 with the D1 mini pro then everything is working fine again........

PS i tried the D1 mini V3 without the SD card shield, same results
PS2 runing Marlin 2.0 bugfix with #define BAUDRATE 250000

[probonopd]

Did you compile yourself for both boards?

[Kotik82]

Yes, compiled myself in both cases.

[Kotik82]

Investigating some more, i see a small difference on the hardware side that might be affecting the issue.

The D1 mini V1 got a 470Ohm resistor on both the RX and TX pins while the D1 mini V3 got no resistors at all.

I need to find a 470Ohm resistor and solder it on the RX pin and see if that changes anything.

[probonopd]

Strange, I am using a D1 mini myself, with a SD card shield. What happens if you use the precompiled one, with and without SD card?

[probonopd]

Never seen a V3...

[Kotik82]

Take a look here, i think it lists the Wemos mini models with their schematics, might come useful.

https://wiki.wemos.cc/products:d1:d1_mini

[Kotik82]

Just uploaded the precompiled bin over OTA, same issue remains.

I don't have a 470Ohm resistor...... need to find one.

[Kotik82]

Ordered the resistors but also got an idea, is it possible to define different pins for RX and TX, essentially redirecting them to different GPIO pins?

If yes then do you have an idea of how to do so?

[probonopd]

I've done that for ESP32 but did not look into it for ESP8266.

Makes me wonder, does serial communication work at all on the V3 modules? Or do we have to consider them as defective?

[Kotik82]

I got the resistors, will have to solder them in tomorrow and will let you know, there is always the possibility that i got a defective module, but while searching the web for similar issues i found another guy that has exactly the same issue with serial communication with a gps module and a V3 module.

[Kotik82]

So, i soldered the resistors (470Ohm) on both TX and RX, still doesn't work. I am out of ideas, its either a defective board or Wemos D1 mini V3 has serial issues.

It is very strange cause everything else works, i can upload files i can upload OTA sketch but there is no communication with the printer.

I give up.

[ipepe]

@Kotik82 Maybe try connecting Wemos to Wemos and check if serial is working?

[probonopd]

Or connect the V3 RX and TX pins to a USB-to-Serial adapter and try talking to it both ways. We need to be sure that the hardware side of things is working at all.

[Kotik82]

So i am back with more info.

Till now my theory was that since TX and RX pins of any ESP8266 are 3.3v tolerant (they might work with 5v logic but it is always better to run them with 3.3v logic)so i need to level shift the 5v TX of the SKR1.3 UART to 3.3v RX on the Wemos.

Things i have tried till now:

1. 1k ohm resistor in series with RX and 2k ohm in parallel with GND ---> didnt work.
2. a zener diode (3.3v) in series with the RX ---> didnt work.
3. flashed ESP3D on the Wemos to see if the UART interface is working ----> working fine..........

So the UART of the Wemos D1 V3 is fine, there is something else going on.

Cause i can control the printer just fine with ESP3D on the same Wemos that refuses to connect with this sketch here.

[ipepe]

Did You build yourself ESP3D or flashed downloaded binary?