# Modbus rs485 serial usb energy meter acquisition TO BE CONTINUED **URL:** \ **Category:** Maker\ **Created:** [September 27, 2023, 3:11pm UTC](https://forum.inductiveautomation.com/t/modbus-rs485-serial-usb-energy-meter-acquisition-to-be-continued/79718 "2023-09-27T15:11:15Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![Thierry\_HOARAU](https://avatars.discourse-cdn.com/v4/letter/t/a5b964/32.png) [@Thierry\_HOARAU](https://forum.inductiveautomation.com/u/Thierry_HOARAU)\ **Post date:** [September 27, 2023, 3:11pm UTC](https://forum.inductiveautomation.com/t/modbus-rs485-serial-usb-energy-meter-acquisition-to-be-continued/79718/1 "2023-09-27T15:11:15Z")
**Hello My project is to connect modbus energy meter with modbus** I need help about how to use Modbus driver - I read [Modbus Address Mapping - Ignition User Manual 8.1 - Ignition Documentation (inductiveautomation.com)](https://docs.inductiveautomation.com/display/DOC81/Modbus+Address+Mapping#ModbusAddressMapping-Stepinuse) **I lunch ignition maker v8** **my serial to USB is COM 4 i check RS485 box instead of 232.** I need to configure adress table Prefix Start End Step Unit ID Modbus Type Modbus Address I need to read MODBUS SLAVE n°1 register = 0 length = 2 register type = 4 : input register 32 bit float and need to swap word to get voltage value modbus doctor is ok I getmesssage IN OPC quick explorer with this adress paramter Prefix Start End Step Unit ID Modbus Type Modbus Address V 0 0 1 INPUT FLOAT 0000 Read completed. [Ignition OPC UA Server]ns=1;s=[Compteur Energie]1.V0 **strong text** Value: null Quality: Bad("Bad\_Timeout: The operation timed out.") Timestamp: 01/01/1601 04:00:00 GST any help apreciated I try to correctly write S30x0000 in Ignition driver format PS : My radix is 10 Im OK with offset 1 for modbus adress value is good 🙂 im happy ! Read completed. [Ignition OPC UA Server]ns=1;s=[Compteur Energie]1.V1 Value: 237.01779 Quality: Good Timestamp: 27/09/2023 20:24:01 GST