Configuring Data Bindings

Data bindings connect DDOs to live data from SAMMI peers. Without bindings, DDOs display default values. This guide explains how to configure the HDA (Host Data Access) properties.

How Data Flows

SAMMI Peer → SAMMI RTE → Gateway (WebSocket) → RuntimeWeb → DDO
  1. A peer (data source) publishes values to the SAMMI RTE
  2. The Gateway bridges SAMMI to web clients via WebSocket
  3. RuntimeWeb subscribes to data keys and routes values to DDOs
  4. The DDO renders the value visually (meter needle, text, bar height, etc.)

HDA Properties

Select a DDO and open the HDA section in the Property Inspector:

General Tab

PropertyDescriptionExample
Data TypeType of data the DDO expectsreal, integer, string
Num ValuesNumber of values from the peer1 (scalar), 6 (multirow)
Refresh TypeUpdate mechanismevent (push), polled
Poll RatePolling interval in ms (if polled)1000

Key Tab

PropertyDescriptionExample
Logical ServerName of the peer providing datapeer_fast, peer_slow
Read KeyVariable name to read fromtemperature, pump_speed
Write KeyVariable name to write to (for input DDOs)setpoint
Key TypeKey data formatdefault

Record Tab

PropertyDescriptionExample
Read RecordRecord identifier for reading—
Write RecordRecord identifier for writing—
Record TypeRecord formatdefault

Common Configurations

Read-Only Display (Meter, Trend, Bar)

Set only the read-side properties:

Logical Server: peer_fast
Read Key: temperature
Data Type: real
Num Values: 1
Refresh Type: event

Read-Write Input (Real, Integer, Alphanumeric)

Set both read and write keys:

Logical Server: peer_slow
Read Key: setpoint
Write Key: setpoint
Data Type: real
Num Values: 1
Refresh Type: event
Enterable: true    (in AFD Input section)

Multirow Display (Real with multiple rows)

Logical Server: peer_fast
Read Key: array_values
Data Type: real
Num Values: 6

The DDO displays all 6 values in rows.

Push Button Command

Push buttons typically don’t read data — they send commands:

Logical Server: $local-cmd    (SAMMI internal command)
Read Key: button_state
Write Key: button_state

Logical Server Names

The logical server name must match a logical_server entry in SAMMI’s s2_config.dat:

logical_server  peer_fast   0x20000010    1   localhost   40  20
logical_server  peer_slow   0x20000020    1   localhost   40  20

Special servers:

  • $local-cmd — SAMMI internal command processor

Testing Without Live Data

If no Gateway is running, DDOs show default values (typically 0 or empty). This is useful for:

  • Layout and positioning work
  • Property configuration
  • Visual design

Once the Gateway and peers are running, DDOs automatically begin displaying live data.

Tips

  • The Read Key is the most important binding — it determines which data the DDO shows
  • Write Key is only needed for input DDOs (enterable Real, Integer, etc.)
  • Match Data Type to the peer’s actual data type to avoid conversion issues
  • Use event refresh for real-time data; polled only when event-driven is unavailable
  • Multiple DDOs can share the same Read Key — they’ll all show the same value

See Also