Wake Over Coax (WoC) for Interface Adapter Modules

Wake Over Coax uses existing PoC voltage on the cable to signal sleep and wake between the source device and remote devices, such as serializers and cameras.

FPD-Link III and FPD-Link-IV do not include a built-in sleep or bidirectional wake-up mechanism. To implement Wake Over Coax, set the PoC voltage to distinct levels. The PoC sink interprets these levels as normal-mode commands or sleep-mode commands.

WoC depends on PoC being active. For details about how the PoC source and sink implement PoC, refer to Power Over Coax for Interface Adapter Modules.

How WoC Works

WoC uses two distinct PoC voltage levels to represent operating states.
  • Normal mode - a higher PoC voltage (for example, 12 V) indicates that the system is active. The remote serializer and downstream devices operate normally.
  • Sleep mode - a reduced PoC voltage (for example, 7–8 V) signals the remote device to enter a low-power state. The serializer can be powered down while the image sensor or other peripherals optionally remain in a low-power surveillance mode.
The PoC source side controls the PoC supply voltage on each channel independently. Transitioning a channel between normal and sleep mode is accomplished by adjusting the programmed PoC output voltage.

Forward Wake-Up (PoC Source Side Wakes PoC Sink Side)

The PoC source initiates a forward wake-up by raising the PoC voltage from sleep-mode level to the normal-mode level. Raising the voltage level signals the sink side to resume operation.

Reverse Wake-Up (PoC Sink Side Wakes PoC Source Side)

If a remote device needs to initiate a wake-up, the system can use a reverse wake-up mechanism. For example, a camera that detects motion while the PoC source side is in sleep mode.

During sleep, the PoC sink signals a wake request by increasing power consumption above a defined threshold. The wake request causes a measurable increase in the PoC supply current on the PoC source side. The PoC source monitors per-channel current during sleep. The PoC source treats any increase that is higher than the threshold as a wake request from the sink.

When the PoC source detects a reverse wake-up, it raises the PoC voltage on affected and sleeping channels. This voltage change returns the system to normal mode.

Relationship to Power Over Coax

WoC is an extension of the PoC feature. WoC shares the same physical infrastructure as PoC. All PoC operating guidelines apply, including safe-disconnect procedures.

Notice Do not set PoC voltage levels that cause a rapid discharge or inrush. Rapid discharge or inrush can damage the interface adapter module or remote device.
Note For safe-disconnect procedures, refer to Power Over Coax for Interface Adapter Modules. For complete API documentation and parameter descriptions, refer to the Wait for PoC Safe to Disconnect VI section in the FlexRIO LabVIEW API Reference.

Support in FlexRIO Interface Adapter Modules

Table 30. WoC Support per Interface Adapter Module
Interface Adapter Module Model WoC Support
IVN-14811 Supported