Modbus RTU vs TCP: Key Differences, Registers, Function Codes, RS-485 Wiring and When to Use Each
Modbus RTU vs TCP explained: registers, function codes, RS-485 wiring, Unit IDs, gateways and security, plus a five-point go-live checklist.
9 min read
SCADA Software & HMI Systems
Run the Site From the Control Room With SCADA and HMI
SCADA and HMI software turns field data from PLCs and RTUs into process mimics, trend charts and alarm lists, so you can monitor and control a site from the control room. We build custom web-based or desktop SCADA that connects to Siemens, Allen-Bradley, Mitsubishi and Schneider PLCs. You own the source code, and there are no additional licence fees.
Whether it is a pumping station, a treatment plant or a production line, the symptoms are the same: operators walk out to the field to read a value, alarms are noticed too late, and PLCs from different vendors each sit behind their own screen. Commercial SCADA platforms solve this, but every extra client and every larger tag count means another licence.
Since 2013, Digital Bridge has developed software and field hardware within the same team. On a SCADA project, that means one point of contact for everything from the PLC connection to the control-room screen, and from alarm notifications to reports. The result: operators see values without walking out to the field, shift supervisors know which alarms are awaiting acknowledgement, and management reports straight from historical data. It works alongside our remote monitoring platform for dispersed sites and our energy monitoring system for line and machine-level consumption.
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What Does Our SCADA and HMI Software Include?
PLC & RTU Integration
PLCs from different vendors appear in one mimic rather than behind separate screens. We connect to Siemens, Allen-Bradley, Mitsubishi, Schneider and other PLCs over Modbus, OPC-UA, Profibus and Ethernet, writing drivers or adapting existing protocols where needed.
Process-Specific HMI Screens
Mimic diagrams, trend charts and gauges that mirror your actual process, so operators understand the situation at a glance. Runs on touch panels, tablets and desktops.
Alarm & Event Management
You hear about problems before it is too late: alarms are raised for limit breaches, equipment faults and process deviations, and sent to the person responsible by email, SMS or push notification. Who acknowledged each alarm, and when, is recorded.
Historical Data & Trends
All sensor data is stored in a time-series database. See from the trend how the process behaved before a fault, compare shifts and generate reports for any period.
User Permissions
Separate access levels for operators, technicians and managers. Critical control commands can require dual approval, and every user action is logged.
Remote & Mobile Access
Secure access from outside the site over VPN. Critical alarms arrive as mobile notifications, and field teams can open mimics and live values on a tablet.
Where Is SCADA Used?
- Water and wastewater treatment
- Food and beverage production lines
- Energy generation and distribution
- Chemical and petrochemical plants
- Cold storage and HVAC
- Pumping and compressor stations
- Textile and weaving production
- Agricultural irrigation systems
Example Scenario: A Pump Stops Overnight
Picture a pump stopping overnight at a booster station. Without SCADA, nobody notices until the reservoir level drops the next morning. With SCADA, the alarm reaches the on-call technician’s phone immediately; the technician checks the current and pressure trends on a tablet and assesses the situation without driving out, while the control-room operator brings the standby pump online within their permissions. Who issued which command, and when, is logged. The same trend data can also feed predictive maintenance work aimed at spotting faults earlier, and if a sensor or interface device is missing on site, our device manufacturing team designs it.
What Are the Steps in a SCADA Project?
01
Site Survey & Tag List
We review your existing PLCs and RTUs, field network and protocols, and draw up the list of data points (tags) with you.
02
Screen & Alarm Design
We design HMI screens and mimics that follow your process flow, and define alarm levels and scaling parameters.
03
Development & Integration
We build the software, connect it to your PLCs and test it, then bring the historian and reporting modules online.
04
Commissioning & Training
We test the system on site and confirm it runs reliably, then train operators and technicians and hand over the documentation.
You Own the Code, With No Licence Fees
On commercial SCADA platforms, licence costs grow with the number of clients and tags. We build the functions you need specifically for your organisation: you own the source code, pay no additional licence fees and are not tied to a single vendor. To carry field data from SCADA into production tracking, we combine it with MES production management in a single data flow.
Questions Asked Before Deciding
If the budget is not yet clear: site assessments for Industry 4.0 projects are free. We do not push off-the-shelf packages; after a needs analysis we set out the scope, phases and cost in a written proposal.
If you are wary of vendor lock-in: with custom SCADA you own the source code, so you can continue developing the system with your own team or another supplier later.
After commissioning: the team that installs the software and hardware also supports it, and technical support is available 24/7.
SCADA Guides
For the building blocks of SCADA and how it differs from HMI and MES, read what is SCADA and how it works. For licensing, source code and total cost, see commercial vs custom SCADA, and for protecting the plant network, our guide to OT security for SCADA. More articles are collected under Industry 4.0 guides.
Share your PLC list or a short description of your site; after the site assessment we will send a written proposal covering scope, phases and cost.
Questions we hear most often
Frequently Asked Questions
What are SCADA and HMI?
SCADA (supervisory control and data acquisition) collects field data from PLCs and RTUs and turns it into process mimics, trend charts and alarm lists. The HMI is the screen where operators see that data and control equipment. Together they let operators monitor and run a site from the control room instead of walking out to the field to read a value.
Which PLC brands and protocols do you work with?
We connect to Siemens, Allen-Bradley, Mitsubishi, Schneider and other PLCs over Modbus, OPC-UA, Profibus and Ethernet. Where needed, we write a driver or adapt the existing protocol. Instead of PLCs from different vendors sitting behind their own screens, they appear together on one screen, in the same process mimic and alarm list.
What does custom SCADA offer over commercial SCADA licences?
On commercial SCADA platforms, licence costs grow with the number of clients and tags. With custom SCADA we build the functions you need for you: you own the source code, pay no additional licence fees and are not tied to a single vendor. The system can be built as web-based or desktop software.
Can the SCADA system be accessed remotely?
Yes. Off-site access runs over a secure VPN connection. Critical alarms arrive as mobile notifications, and field teams can reach process mimics and live values from a tablet. Separate permission levels are set for operators, technicians and managers, critical control commands can require dual approval, and every user action is logged.
What are the steps in a SCADA project?
We first review your PLCs and RTUs, site network and protocols, and agree the list of data points (the tag list) with you. We then design HMI screens around the process flow and define alarm levels, develop the software, connect it to the PLCs and test it. Finally, we commission the system on site, train operators and technicians, and hand over the documentation.
What is the difference between SCADA and a PLC?
A PLC is an industrial controller that runs a machine or process directly: it reads sensors and drives motors or valves according to its program. SCADA is the supervisory layer above it that collects data from many PLCs and RTUs, shows values on process mimics, stores their history, raises alarms and lets authorised operators send commands. In short, the PLC runs the field and SCADA lets you oversee it from one screen.
How is the cost of a SCADA project set, and how do we start?
We have no off-the-shelf price list; the cost depends on the scope of the project. Site assessments for Industry 4.0 projects are free: we review your PLCs and RTUs, site network and the points to be monitored on site, then send a written proposal covering scope, phases and cost after a needs analysis. With custom SCADA you own the source code and pay no additional licence fees, and technical support is available 24/7 after commissioning.
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