I’ve just started working with the PortServer TS 4 W and have been able to successfully communicate with a RS-232 device over our ethernet network.
What I’m trying to do next is to communicate with a RS-485 2-wire device – but I’m unable to do so - no data is coming back or seems to be received by the device.
I configured the DIP switches for RS-485 half-duplex with termination. Without termination, the data is echoed back to me.
The RS-485 2-wire device is a robot servo motor with a D- & D+ with power and ground.
I wired my robot servo motor according to the table on page 111 in the TS PortServer manual for 485 2-wire mode
, i.e. D- to pin 2 and D+ to pin 6. Pin 4 CGND and Pin 7 SGND were tied to the ground from the power supply for my servo motor. I’ve also made sure that my baud rates were set correctly too.
One thing that comes to mind right away is the pinout. Digi uses a 10-pin RJ45 connector on the device, not a standard 8-pin RJ45 (such as a CAT5/6 cable). If you are using an 8-pin cable, you will need to set this up slightly different. Pin 1 would now be Data-, Pin 5 would be Data+, and SG is now on Pin 6. I would check this out if you are using an 8-pin RJ45 connector.
I’m using a 10-pin RJ-45 connector that fits snuggly into the serial port interface.
Currently, I’ve been able to send data over the ethernet to the RS-485 2-wire device, but wasn’t able to receive data back.
I’ve re-wired it as: d- of the robot servo to the PortServer TxD- pin 1 and d+ of the robot servo to the PortServer TxD+ pin 5. I was only able to transmit to the motor when I connected 110 ohm termination resistor between d+ and d-.
After the transmit worked I tried connecting in RxD- from the PortServer to d- of the motor and RxD+ to d+ too, I wasn’t able to transmit data as I was before even with the transmit lines intact (as well as receive data).
Is there an “Enable RTS Toggle” setting to switch RS-485 half duplex send and receive modes automatically? The Support Wizards said there was such a setting, but they haven’t gotten back to me yet as to where I can find it. I didn’t see any mention of it in the manual, nor did I see this setting in the TS 4 W PortServer web-page configuration manager.
Log in with your browser, under Confiiguration, Serial Ports, select the port you wish to change, Advanced Serial Settings, and you should see a check box "Enable RTS Toggle. Check the box, hit the Apply button and reboot the unit.
RTS Toggle will be enabled.
It seems that the Toggle RTS option is only available when the dip switches are set for RS-232. When I switch the port to RS-485, the option disappears.