SNAP Hooks

SNAP hooks help provide a method for Event-Driven Programming in SNAPpy. There are a number of events in the system that can invoke a SNAPpy function. Use the setHook() function decorator to associate your SNAPpy function with one the following events:

HOOK_STARTUP

HOOK_STARTUP

Called on device bootup.

Example

@setHook(HOOK_STARTUP)
def onBoot():
    pass

HOOK_GPIN

HOOK_GPIN

Called on transition of a monitored hardware pin.

Parameters

  • pinNum (int) – The pin number of the pin that has transitioned.

  • isSet (bool) – A Boolean value indicating whether the pin is set.

Example

@setHook(HOOK_GPIN)
def pinChg(pinNum, isSet):
    pass

See also

HOOK_1MS

HOOK_1MS

Called every millisecond.

Parameters

tick (int) – A rolling 16-bit integer incremented every millisecond, indicating the current count on the internal clock. The same counter is used for all four timing hooks.

Example

@setHook(HOOK_1MS)
def doEvery1ms(tick):
    pass

HOOK_10MS

HOOK_10MS

Called every 10 milliseconds.

Parameters

tick (int) – A rolling 16-bit integer incremented every millisecond, indicating the current count on the internal clock. The same counter is used for all four timing hooks.

Example

@setHook(HOOK_10MS)
def doEvery10ms(tick):
    pass

HOOK_100MS

HOOK_100MS

Called every 100 milliseconds.

Parameters

tick (int) – A rolling 16-bit integer incremented every millisecond, indicating the current count on the internal clock. The same counter is used for all four timing hooks.

Example

@setHook(HOOK_100MS)
def doEvery100ms(tick):
    pass

HOOK_1S

HOOK_1S

Called every second.

Parameters

tick (int) – A rolling 16-bit integer incremented every millisecond, indicating the current count on the internal clock. The same counter is used for all four timing hooks.

Example

@setHook(HOOK_1S)
def doEverySec(tick):
    pass

HOOK_STDIN

HOOK_STDIN

Called when “user input” data is received.

Parameters

data (str) – A data buffer containing one or more received characters.

Example

@setHook(HOOK_STDIN)
def getInput(data):
    pass

See also

HOOK_STDOUT

HOOK_STDOUT

Called when “user output” data is sent.

Example

@setHook(HOOK_STDOUT)
def printed():
    pass

See also

HOOK_RPC_SENT

HOOK_RPC_SENT

Called when the buffer for an outgoing RPC call is cleared.

Parameters

bufRef (int) – An integer reference to the packet that the RPC call attempted to send. This integer will correspond to the value returned from getInfo(9) when called immediately after an RPC call is made. The receipt of a value from HOOK_RPC_SENT does not necessarily indicate that the packet was sent and received successfully. It is an indication that SNAP has completed processing the packet.

Example

@setHook(HOOK_RPC_SENT)
def rpcDone(bufRef):
    pass

See also