Specifications

Comedi
51 / 148
Synopsis
#include <comedilib.h>
int comedi_command(comedi_t * device, comedi_cmd * command);
Description
The function comedi_command() starts a streaming input or output. The command structure pointed to by command specifies
settings for the acquisition. The command must be able to pass comedi_command_test() with a return value of 0, or com-
edi_command() will fail. For input subdevices, sample values are read using the function read() on the device file. For output
subdevices, sample values are written using the function write().
Return value
If successful, 0 is returned, otherwise -1.
5.4.2.3 comedi_command_test
comedi_command_test — test streaming input/output configuration
Synopsis
#include <comedilib.h>
int comedi_command_test(comedi_t * device, comedi_cmd * command);
Description
The function comedi_command_test() tests the command structure pointed to by the parameter command and returns an
integer describing the testing stages that were successfully passed. In addition, if elements of the comedi_cmd structure are
invalid, they may be modified. Source elements are modified to remove invalid source triggers. Argument elements are adjusted
or rounded to the nearest valid value.
The meanings of the return value are as follows:
• 0 indicates a valid command.
• 1 indicates that one of the ..._src members of the command contained an unsupported trigger. The bits corresponding to
the unsupported triggers are zeroed.
• 2 indicates that the particular combination of ..._src settings is not supported by the driver, or that one of the ..._src
members has the bit corresponding to multiple trigger sources set at the same time.
• 3 indicates that one of the ..._arg members of the command is set outside the range of allowable values. For instance, an
argument for a TRIG_TIMER source which exceeds the board’s maximum speed. The invalid ..._arg members will be
adjusted to valid values.
• 4 indicates that one of the ..._arg members required adjustment. For instance, the argument of a TRIG_TIMER source may
have been rounded to the nearest timing period supported by the board.
• 5 indicates that some aspect of the command’s chanlist is unsupported by the board. For example, some analog input boards
require that all channels in the chanlist use the same input range.
5.4.2.4 comedi_get_buffer_contents
comedi_get_buffer_contents — streaming buffer status