define(`TITLE', `A simple Modbus RTU to TCP gateway') define(`DATE', `2014-10-27') define(`CONTENT', ` Meterbus is a great Thing, especially as two-wire slave (bus-powered) are possible. Unfortunately the Meterbus Transceiver TSS721A is rather expensive and not that easy to obtain. So, I decided to test another fieldbus: Modbus. A Modbus Transceiver (here: LTC485) is much cheaper than the TSS721A and moreover a 1-phase powermeter with Modbus interface is about 30€, a 1-phase powermeter with Meterbus interface is about 90€. I found some Arduino libraries for both Modbus RTU and Modbus TCP on the Net so I started with a simple Modbus master talking to a 1-phase powermeter: Communication works: (Blue and yellow are the Modbus lines, purple is TX at the microcontroller, green is RT at the microcontroller.) ')