Telemetry of remote objects via GSM modem SPRUTNET PRO BGS2
What are modems for ..? The question is rather rhetorical.
Transferring data from point A to point B, without spending time and effort on physical movement - their main purpose. Let us consider the problem of taking readings from metering devices via the GSM channel, which is relevant for many.
Of the many models on the market, SPRUTNET PRO BGS2 was chosen, primarily because of the relatively low price - 3900 rubles, and secondly, the developers offer free samples for testing. Another plus is that to organize a communication channel there is no need to purchase two modems - it is only needed directly at the facility, and on the operator's side, special software is installed that converts incoming TCP connection packets into a virtual COM port, to which you can already connect any user program.
The main reason that convinced me to choose this particular model was the presence on Sprutnet PRO of two interfaces for communication with external equipment at once - RS232 and RS485. Due to the fact that the modem was supposed to be installed at the heating unit of an apartment building, where there are devices with both interfaces, the choice was made.
To order a modem for testing, you can chat directly in the chat on the SPRUTNET PRO BGS2 website with a pleasant and technically competent manager who will help you choose the right model. For example, I needed a modem with data transmission via GPRS, although a model using a CSD connection may be more suitable for someone.
So, the package has arrived, the modem is in hand - let's start experiments. It looks pretty solid, metal case, connectors for external connections for a screw. My modem has two slots for SIM cards, i.e. the possibility of reservation of the communication channel is provided.
The modem is configured via the USB interface, for which you must first install the driver from the download page. In general, developers are in order with documentation and software, there is no need to look for anything separately, everything is in one place.
For configuration, you need to get the SIM card out of the modem, otherwise, when turned on, it will go into operating mode. The whole setup is described in the documentation, it takes a couple of minutes. During the configuration, an unexpected fact was revealed - in the line of the IP address with which the connection was established, a static, white address must be indicated! Let it be so, the obstacle is completely surmountable.
For the sake of experiment, I checked whether there will be a connection through a gray dynamic address. Yes, everything works, BUT until the next reboot of the router, after which it is necessary to drive a new connection address into the modem again - not the best option. The problem was solved by registration with a provider under a dedicated IP contract. In Rostelecom, this service costs 130 rubles. when connected and further 80r. per month. By the way, I also tried to exit via VLAN, but the problem is that the ports needed for exchange in this way could not be transferred. Maybe there is a way, but time is money, so it was easier to negotiate with the provider.
So, the modem is configured. It remains to install the necessary software on the PC. This software is based on Eltima developments and is essentially a paid product, but if you wish, you can find demo versions. I recommend contacting Sprutnet technical support, they helped me find the right version of the IP adapter, which was not on the site.
As a result, when launched, this utility hangs in the tray and creates two interconnected virtual COM ports. One receives packets from an external TCP connection, the other is directly connected to any user program - a hyperterminal, software for polling meters or a SCADA system.
All. It remains to supply power to the modem and observe the process of establishing a connection. For verification, manufacturers recommend hanging an external jumper between Tx and Rx (pins 2 and 3) on the connector.
Some time after the start of the IP adapter, a message about the connected modem appears in the log. To check the connection, you can launch a hyperterminal, in the connection properties of which the second port from the linked pair is indicated, in the figure it is COM8.By pressing the buttons on the keyboard, we get a return echo through the jumper on the modem with some delay. On the modem, when the connection is established, the red indicator is constantly on.
The channel is working, now you can connect external devices.
In my case, this is a VKT-7 heat calculator and a TRM32 heating controller made by Aries. Communication with the first is carried out via the RS232 interface, with the second - via RS485. By the way, this device was originally purchased from the factory in a budget version - without communication interfaces, we had to install the missing elements, since the firmware is the same for both versions.
To poll both devices, you don't need to reinvent the wheel, manufacturers have taken care of various software options for taking readings, up to OPC servers. For example, for VKT-7, all the necessary software can be found on the developer's or dealers' website. The same goes for the TPM32, which is included in the list of supported devices in the Aries OPC server.
The only caveat is that the indicated devices must be interrogated, of course, in turn, because interfaces 232 and 485 on the modem in fact occupy one channel and differ only in circuitry.
It is too early to draw general conclusions, the modem is installed at the facility, further operation will show all the pros and cons.