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MarkoV edited this page Oct 12, 2025 · 1 revision

Automation & Node-RED

BenchMesh integrates with Node-RED to provide powerful automation capabilities for your lab instruments.

What is Node-RED?

Node-RED is a visual programming tool for wiring together hardware devices, APIs, and online services. With BenchMesh, you can:

  • Create automated test sequences
  • Log measurements to databases or files
  • Build complex workflows with conditional logic
  • Integrate with other lab systems
  • Schedule periodic measurements

Accessing Node-RED

Node-RED runs on port 1880 when started via ./start.sh:

URL: http://localhost:1880

BenchMesh Custom Nodes

BenchMesh provides custom Node-RED nodes for instrument control:

Available Nodes

  1. benchmesh-status - Get device status and measurements
  2. benchmesh-call - Call device methods (control instruments)
  3. benchmesh-instruments - List all configured instruments

Installing Custom Nodes

BenchMesh nodes are automatically available when starting via ./start.sh.

To install manually in an existing Node-RED instance:

cd ~/.node-red
npm install /path/to/BenchMesh/benchmesh-nodered-nodes

Restart Node-RED after installation.

Using BenchMesh Nodes

Getting Device Status

The benchmesh-status node retrieves current device measurements:

  1. Drag benchmesh-status node to the flow
  2. Double-click to configure:
    • Device ID: Enter device ID from config (e.g., psu-1)
    • API Base: Usually http://localhost:57666
  3. Connect to a debug or processing node
  4. Deploy the flow

Output: Device status object with current measurements

Example output for PSU:

{
  "voltage": 5.00,
  "current": 0.15,
  "output": true
}

Calling Device Methods

The benchmesh-call node executes device control commands:

  1. Drag benchmesh-call node to the flow
  2. Double-click to configure:
    • Device ID: Target device
    • Method: Method name (e.g., set_voltage)
    • Arguments: JSON array of arguments
    • API Base: http://localhost:57666

Example configurations:

Set PSU voltage to 5V:

  • Device ID: psu-1
  • Method: set_voltage
  • Arguments: [5.0]

Set PSU output ON:

  • Device ID: psu-1
  • Method: set_output
  • Arguments: [true]

Set voltage with channel:

  • Device ID: psu-dual
  • Method: set_voltage
  • Arguments: [5.0, {"ch": 1}]

Listing Instruments

The benchmesh-instruments node returns all configured devices:

  1. Drag benchmesh-instruments node to the flow
  2. Configure API base if needed
  3. Connect to processing nodes
  4. Deploy

Output: Array of instrument objects with ID, name, driver, and class information

Example Flows

Example 1: Periodic Voltage Monitoring

Monitor PSU voltage every 5 seconds and send alerts if out of range:

[inject (5s)] → [benchmesh-status] → [function: check range] → [debug/alert]
  1. Inject node: Set to repeat every 5 seconds
  2. benchmesh-status: Device ID = psu-1
  3. Function node: 
    const voltage = msg.payload.voltage;
if (voltage < 4.9 || voltage > 5.1) {
    msg.payload = `Voltage out of range: ${voltage}V`;
    return msg;
}
return null;
  4. Debug node: Display alerts

Example 2: Automated Test Sequence

Ramp PSU voltage and log current measurements:

[inject] → [function: ramp] → [benchmesh-call] → [delay 100ms] → [benchmesh-status] → [csv]
  1. Inject node: Manual trigger
  2. Function node (ramp generator): 
    const voltages = [0, 1, 2, 3, 4, 5];
const messages = voltages.map(v => ({
    payload: {
        device_id: "psu-1",
        method: "set_voltage",
        args: [v]
    }
}));
return [messages];
  3. benchmesh-call: Set voltage
  4. Delay: Wait for settling
  5. benchmesh-status: Read current
  6. CSV node: Log to file

Example 3: Multi-Device Coordination

Control PSU and monitor with DMM simultaneously:

[inject] → [benchmesh-call: PSU] → [delay] → [benchmesh-status: DMM] → [function: log]
  1. Set PSU voltage
  2. Wait for settling time
  3. Read DMM measurement
  4. Log correlated data

Working with Node-RED

Creating a New Flow

  1. Open Node-RED: http://localhost:1880
  2. Drag nodes from the left palette
  3. Wire nodes together by connecting output to input
  4. Double-click nodes to configure
  5. Click Deploy to activate

Debugging Flows

  1. Add debug nodes to outputs
  2. View output in the right sidebar (bug icon)
  3. Use catch nodes for error handling
  4. Enable node status messages

Importing/Exporting Flows

Export:

  1. Select nodes (or Ctrl+A for all)
  2. Menu → Export → Clipboard
  3. Save JSON to file

Import:

  1. Menu → Import → Clipboard
  2. Paste JSON
  3. Click Import

Node-RED Resources

API-Based Automation

You can also automate without Node-RED using the REST API directly.

Example: Python Script

import requests
import time

API_BASE = "http://localhost:57666"

# Set PSU voltage
requests.post(f"{API_BASE}/api/call", json={
    "device_id": "psu-1",
    "method": "set_voltage",
    "args": [5.0]
})

# Wait for settling
time.sleep(0.5)

# Read status
response = requests.get(f"{API_BASE}/instruments")
instruments = response.json()
psu = next(i for i in instruments if i["id"] == "psu-1")
print(f"Voltage: {psu['status']['voltage']}V")

Example: Bash Script

API_BASE="http://localhost:57666"

# Set voltage to 3.3V
curl -X POST "$API_BASE/api/call" \
  -H "Content-Type: application/json" \
  -d '{"device_id":"psu-1","method":"set_voltage","args":[3.3]}'

# Get status
curl "$API_BASE/instruments" | jq '.[] | select(.id=="psu-1") | .status'

Best Practices

  1. Error Handling: Always add catch nodes for error handling
  2. Rate Limiting: Don't poll too frequently (max 1-2 Hz recommended)
  3. Logging: Use file or database nodes for persistent logs
  4. Testing: Test flows with single inject before automation
  5. Documentation: Add comment nodes to document complex flows
  6. Backups: Export flows regularly

Troubleshooting

BenchMesh Nodes Not Appearing

  • Restart Node-RED after installation
  • Check ~/.node-red/package.json includes benchmesh nodes
  • View Node-RED startup logs for errors

API Connection Failed

  • Verify BenchMesh backend is running (http://localhost:57666/docs)
  • Check API base URL in node configuration
  • Ensure firewall allows local connections

Method Call Errors

  • Verify device ID matches configuration
  • Check method name spelling (case-sensitive)
  • Ensure arguments match method signature
  • View debug output for error messages

Advanced Topics

Custom Dashboard

Create a Node-RED dashboard for monitoring:

  1. Install dashboard: npm install node-red-dashboard
  2. Use dashboard nodes (gauge, chart, button)
  3. Access at http://localhost:1880/ui

MQTT Integration

Publish measurements to MQTT:

  1. Install MQTT nodes
  2. Configure MQTT broker
  3. Publish device status to topics

Database Logging

Store measurements in database:

  1. Install database nodes (MySQL, PostgreSQL, InfluxDB)
  2. Create logging flow
  3. Query historical data
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