I wanted to ask a few questions about the difference between a genuine “Arduino Uno” and a “WeMos D1 CH340 WiFi Arduino Uno R3 compatible development board esp8266 ESP-12E”. I’m very green at this and was recently on this forum asking for help with my sketch for an HX711 load cell scale that I was building. I received some help from some great people and now I have a working sketch using my genuine “Arduino Uno”. What I would like to do now is build another scale, but this time I want to use the WeMos D1 as the microcontroller. I understand that you have to install the CH340 driver and you have to install the ESP8266 boards to the board’s library. I wanted to ask about the pin assignments. The boards look very similar but I’m a little confused about the pin markings on the WeMos D1 board. I have inserted a pinout diagram of the WeMos D1.
On my Arduino Uno, to connect the HX711, I used pin 4 for data and pin 5 for clock. On the WeMos D1, could I use D4 for data and D5 for clock?
On my Arduino Uno, to connect the 128 X 32 OLED display I used the A4 pin for data and A5 pin for clock. What pins on the WEMos D1 should I use for clock and data from the OLED?
It looks like the WeMos D1 has a 3.3V logic level, whereas the Arduino Uno operates at 5 volts. Will this cause any issues that I have to address?
When I change the code to reflect the different pins do I use the numbers in red shown in the above diagram? For example (const int HX711_dout = D4;)
When I choose a board in the IDE I see one called “LOLIN(WeMos) D1 R1”. Would this be the correct board to pick?
Thanks for any help.
Yes, Arduino pins are defined with their number, e.g. 4 and 5, but with WeMos you must use specific symbols, with "D" prefix (instead of 4 you must write D4). You can see the reason on the serigraphs next to each pin.
WeMos/ESP8266 boards don't have A4 and A5. There's just one analog pin.
But if the device is I2C, use D14 and D15 for SDA and SCL, like the picture you posted clearly shows .
This depends on the devices you need to interface. What kind of devices are we talking about?
Yes, it's the same of the first point.
If it's an R1 ("release 1") board, yes.
On newer one like R2 or Mini you will obviously choose "D1 R2 & mini".
I have never used an HX711, thus I can't say anything about it, anyway it's always a good idea to check the device datasheets for 3.3V compatibility.
For example, if your OLED has an SSD1306 chip it can be controlled with 3.3V, but if the board includes level shifters like BSS138 for SDA/SCL could require a TTL 5V input.
Anyway, always check the datasheets of the specific items you intend to use.
