Notes on Lollette LE3U PLC

• Lollette LE3U is a “copy” of the Mitsubishi FX3U PLC for $60 on AliExpress while the original costs around $1000.
• All configuration is done using Mitsubishi’s proprietary software GX Developer or GX Works2 which cost another $500 but have a 60-day free trial available online.
• It features 14 digital inputs, 6 analog inputs, 2 analog output and 10 relay outputs.
• The RS485 port is not configured by default so you can’t control any of the relays or read input values without first uploading new configuration program.
• Programming is done using visual Ladder language which is somewhat confusing to get started until you realise that it’s pretty much a mapping of input triggers, registers and their values.
  • Each physical input maps to a register which can then change another output register depending on certain rules.
  • Configuring parameters is “moving” 1-byte or 2-byte strings into registers.

Configure RS485 Modbus

To configure the device as a Modbus “slave”, hook into the M8002 event and configure the following registers:

• D8120 with the details for the serial protocol. Set it to H4081 to enable Modbus RTU slave protocol with 8 data bits, 0 parity bits, 1 stop bit and a 9600bps transfer rate.
• D8121 for the device ID or station number. Set to K1 where 1 is the device ID.
• D8129 for the communication timeout (optional). Set to K100 where 100 is the timeout in milliseconds.

The 4-byte values are entered as a string of matching hex values starting from the lowest bit (please ignore the actual register values since this is from a different device):

See these two videos for detailed instructions:

• How to Configure PLC as a Modbus Slave and how to read write the data from PLC through Modbus
• Control FX3U PLC with ESP32 Microcontroller Part 1 (PLC I/O Control) and Part 2