I’m sorry, but you keep saying things that are unclear and incomplete which makes it very frustrating for me in trying to help you. I need you to share more information.
Do you have or have you read the manual from Yosemitch for your sensor and do you understand how it works? I am not specifically familiar with the Y500-B; I assume it can be interacted with like a Y502.
Have you ever succeeded in communicating with this sensor – that is, using your computer, a hand-held Yosemitech transmitter, an AVR based Arduino, or any other device that is NOT your Node MCU board?
Do you know your sensor’s modbus address? That information is required.
Now describe completely your physical wiring and connections:
- Are you using breadboards or have you made a custom circuit of some kind? Post a picture.
- By what is the Yosemitch sensor powered and at what voltage?
- Exactly what RS485 to TTL adapter do you have connected between the A and B (green and white) of your Y500B and your NodeMCU (brand, chipset, etc)
- What powers the RS485 adapter and at what voltage?
- Does the adapter require the use of a pin to change the direction of communication or does it have automatic flow control?
- Are there any LED’s on your adapter?
- If so, do you see the power, Tx, and Rx LED’s light up appropriately?
- What level shifters are you using (brand, etc)?
- Are your level shifters between the Tx and Rx of your adapter and the pins of your NodeMCU?
- If not, where are they in the chain?
- What voltages are you shifting to and from?
- I have not succeeded in using external level shifters on a breadboard with an RS485 adapter so I am quite skeptical of a set-up that requires them.
- Are you sure you have Tx and Rx coming out of the adapter connected appropriately the pins you are assigning as Rx and Tx in SoftwareSerial?
- Have you tried reversing the Tx and Rx?
In your code, what version of the Yosemitch library, of SensorModbusMaster, and of the Arduino core for ESP8266 do you have installed? Please list the versions and post your complete code.