[nwritten, when, errmsg, prewritetime, postwritetime, lastchecktime] = IOPort(‘Write’, handle, data [, blocking=1]);
Write data to device, specified by ‘handle’.
‘data’ must be a vector of data items to write, or a matrix (in which case data
in the matrix will be transmitted in column-major order, ie., first the first
column, then the 2nd column etc…), either with data elements of uint8 class or
a (1 Byte per char) character string. The optional flag ‘blocking’ if set to 0
will ask the write function to not block, but return immediately, ie. data is
sent/written in the background while your code continues to execute - There may
be an arbitrary delay until data transmission is really finished. The default
setting is 1, ie. blocking writes - The function waits until data transmission
is really finished. You can also use blocking == 2 to request a different mode
for blocking writes, where IOPort is polling for write-completion instead of a
more cpu friendly wait. This may decrease latency for certain applications.
Another even more agressive polling method is implemented via blocking == 3 on
Linux systems with some limited set of hardware, e.g., real native serial ports.
On systems without any support for specific polling modes, the 2 or 3 settings
are treated as a standard blocking write.
Optionally, the function returns the following return arguments:
‘nwritten’ Number of bytes written – Should match amount of data provided on
‘when’ A timestamp of write completion: This is only meaningful in blocking
‘errmsg’ A system defined error message if something wen’t wrong.
The following three timestamps are for low-level debugging and special purpose:
‘prewritetime’ A timestamp taken immediately before submitting the write
request. ‘postwritetime’ A timestamp taken immediately after submitting the
write request. ‘lastchecktime’ A timestamp taken at the time of last check for
write completion if applicable.