Operator Reference
query_io_device (Operator)
query_io_device
— Query information about channels of the specified I/O device.
Signature
query_io_device( : : IODeviceHandle, IOChannelName, Query : Result)
Description
The operator query_io_device
returns information about
transmission channels of a specified I/O device. The handle to the
I/O device is passed to in IODeviceHandle
, whereas the
channels are addressed by IOChannelName
. The desired
information about the I/O channels is specified via Query
.
A list of all supported channel names is usually returned when passing
'io_channel_name' to Query
while the input
parameter IOChannelName
is ignored.
Please check the directory doc/html/reference/io
for documentation about your specific I/O device interface, where
all supported channel-specific parameters are listed.
Execution Information
- Multithreading type: reentrant (runs in parallel with non-exclusive operators).
- Multithreading scope: global (may be called from any thread).
- Processed without parallelization.
Parameters
IODeviceHandle
(input_control) io_device →
(handle)
Handle of the opened I/O device.
IOChannelName
(input_control) string(-array) →
(string)
Channel names to query.
Query
(input_control) string-array →
(string)
Name of the query.
Default: 'param_name'
List of values: 'io_channel_names' , 'param_name'
Result
(output_control) string-array →
(string / integer / real)
List of values (according to Query
).
Example (HDevelop)
* Select a suitable i/o device interface of name IOInterfaceName query_io_interface (IOInterfaceName, 'io_device_names', DeviceNames) open_io_device (IOInterfaceName, DeviceNames[0], [], [], IODeviceHandle) query_io_device (IODeviceHandle, [], 'io_channel_names.digital_input', \ ChannelInputNames) open_io_channel (IODeviceHandle, ChannelInputNames[0], [], [], \ IOChannelHandle) read_io_channel (IOChannelHandle, Value, Status)
Result
If the parameters are valid, the operator
query_io_device
returns the value 2 (
H_MSG_TRUE)
. If necessary an
exception is raised. In this case, an extended error information may be
set and can be queried with the operator get_extended_error_info
.
Possible Successors
Module
Foundation