Exposing RSSI, RSCP, etc. to Modbus registers

Hi all:

I’d like to be able to transmit my remote gateway’s signal strength via Modbus to my SCADA system. I’m more familiar with SixNet RAM series gateways which have built-in automation functions that can accomplish this.

Is there a means to achieve this on GX450 gateways?

Thanks!

Hi willpoll,

I am not aware that any ALEOS gateway has a feature designed to send status values right out of the box via serial. The only way I can see this working would be to first query the gateway using AT commands and sending that information over to the SCADA system. Typically you’d use SNMP, ALMS, or Events Reporting feature in AceManager to send statuses over the air, not serial.

Regards,
Nick

Thanks Nick,

Definitely more complicated than I wanted, but do-able. I’ll hook my PLC to the serial port, create a custom protocol handler to issue the AT command, parse the response, and place the value into a Modbus register.

Oh well, good skills to practice.

Thanks again,

Will

I have a similar problem in front of me and just getting started with ALEOS. Does anyone have some sample code to point me in the right direction?

  • Jef

Basically, I connected the RS232 port on my PLC to the RS232 on the modem 115200,N,8,1 is default setting.

Via that port I send a ATLTERSRP? and then parse the response to get RX power as an integer, I do the same with ATLTERSRQ? for signal quality.

PLC code is platform specific so unless you’re using Automation Direct DoMore PLC my code won’t help much.

-Will

Thanks Will. That makes complete sense.

In my case, I have few very simple SCADA sites that need to communicate, via Modbus, when polled, whether the device supply voltage is above a certain level, and whether a digital point is high or low.

So, I want to have code that provides these two points that can be sensed directly by the RV50X, to avoid adding an external device speaking Modbus RTU. I need code that can simulate a simple PLC.

  • Jef

  • Jef

Jef:

I don’t have RV50X, but I did just look through the entire ALEOS 4.8.0 User Guide for AirLink
RV50 Series and didn’t see any info on Modbus registers, so I don’t know how you would even expose the status of digital input to Modbus, almost seems like it will only act as a gateway but not be a Modbus device itself.

-Will

You might look at AT*DIGITALINn command, not Modbus but do-able with a PC, PLC or micro like a Pi or Arduino.

-Will

Thanks Will.

My thought was that even without a library to emulate Modbus registers, I should be able to use ALEOS to capture the current supply voltage, and capture the current status of the single discrete I/O wire. Then, I can parse Modbus requests coming in (there will be only two to respond to) and package up those two captured values and send them back in Modbus format.

This would allow me to handle the needs of these very simple SCADA sites (just power fail and a single discrete input) without extra hardware beyond the RV50 itself.

But right now, I’m struggling to get through the AAF tutorial (hello program) since it seems to not match the V2.0 Development Studio…

  • Jef