This is my first serious in depth attempt at serial communications so have patients with my lack of knowledge.

My goal is to be able to connect a Hitachi L200 VFD to a PC for basic remote control. The L200 is RS485 Modbus RTU network compatible. My first attempt to connect the VFD was done using a RS485 PCI card and the ProDrive software from Hitachi. After failing to make that setup work I contacted Hitachi. Their recommendation was to purchase there "ConverterCable" that converts RS232 to RS422. According to Hitachi using this cable in conjunction with their ProDrive software should lead to a successful setup. Even with this new setup I get the same problems. Sorry about the long background story....

Currently I am using a baud rate of 4800bps, no parity, 8 bit and 1 stop bit (these settings are used in the settings of ProDrive, RS232 communications port and the L200). When using ProDrive it says that it is unable to receive a signal from the VFD. However in ProDrive you can see an echo of the transmitted signal. When using comtest or hyperterminal on the communications port I am also getting an echo of the transmitted signal (regardless of what the signal is). This echo is only present though when the L200 is plugged into the com port. On the positive side when I do try to communicate with the L200 it responds with an error code of E60 (which states that there was a communication error). I am really confused why this isn't working and am looking for additional things to try and troubleshoot.

Some of my points of confusion are...

Is RS422 always full duplex or can it also be half duplex and therefore compatible with L200's 2 wire RS485. I am assuming that the converter cable's output does not need any further modifications. An example of a modification I have been considering to go from full duplex to half duplex is to short the TXD+ with RD+ and TXD- with RD-. But who knows...

If the system is half duplex then what settings should I try to adjust to verify that the VFD and PC aren't trying to talk at the same time? Communication wait time setting on the VFD? what about on the PC?

Any help is appreciated...

Thanks,
-Pat

 

After some struggles I finally got Prodrive to talk to an SJ200 drive. My conclusions for what they are worth:-

1. Standard control panel, and Prodrive use RS422 (4 wire). Make sure the switch behind the terminal cover is set to OPE not 485. 2-wire RS485 is for network comms with PLCs etc not for talking to Prodrive.

2. The Inverter Manual doesn't give the full pinout details for RS422, only for RS485. I eventually found the info I needed buried in the manual for a Hitachi TCP/IP Modbus adapter ->

The RJ45 socket behind the control panel wiring is as follows for RS422

2 Rx+
3 Rx-
5 Tx+
6 Tx-
7 GND

Hope that helps.

 

http://www.ctiautomation.net/PDF/Hitachi/Hitachi-SJ200-VFD-Drives.pdf

 

I'm new to networking.Can i connect the Hitachi Sj200(Rs 485) with PC (rs232) DOPPro without any converter card.
Pls any one????