Table of Contents
hil_read_digital_buffer
Reads the specified number of samples from the digital channels at the indicated sampling rate.
Description
The hil_read_digital_buffer function reads the specified number of samples from the digital input channels at the given sampling rate. The function does not return until the data has been read.
Many cards allow the digital I/O lines to be programmed as inputs or outputs. The digital I/O lines are configured as inputs or outputs using the hil_set_digital_directions function. All the channels which will be used as digital inputs must be configured as inputs using this function. Failure to configure the digital I/O may result in the hil_read_digital_buffer function failing to read those inputs.
Prototype
t_error hil_read_digital_buffer(t_card card, t_clock clock, t_double frequency, t_uint32 num_samples, const t_uint32 digital_channels[], t_uint32 num_channels, t_boolean buffer[]);
Parameters
t_card card
A handle to the board, as returned by hil_open
t_clock clock
The clock used to time the operation. Note that some clocks allow faster sampling rates than others. See Clocks for more information on clocks.
Select a board type from the list for board-specific details: .
t_double frequency
The frequency in Hertz at which to sample the digital input channels. For example, if frequency is set to 1000, then the hil_read_digital_buffer function will read all the selected channels every millisecond.
t_uint32 num_samples
The number of samples to collect. Each "sample" consists of all the digital input channels specified. For example, if frequency is set to 1000 and num_samples is set to 5000, then the hil_read_digital_buffer function will return after 5 seconds with 5000 samples. If 3 channels have been selected, then the output buffer will contain 15,000 elements.
const t_uint32 [] digital_channels
An array containing the channel numbers of the digital inputs to be read.
Select a board type from the list for board-specific details: .
t_uint32 num_channels
The number of channels specified in the digital_channels array.
t_boolean [] buffer
An array for receiving the values read from the digital inputs. The array must contain num_channels * num_samples elements. The array is organized as a linear array of samples, with each sample consisting of a group of channels. For example, if digital input channels 0, 1 and 3 are being read, than the data appears in the array as follows, where the numbers correspond to channel numbers:
0 |
1 |
3 |
0 |
1 |
3 |
... |
This ordering is equivalent to defining the buffer as:
t_boolean buffer[num_samples][num_channels];
If the buffer is defined this way then pass the buffer as the buffer
argument using the syntax: &buffer[0][0]
.
Return value
The return value is the number of samples successfully read. Otherwise a
negative error code is returned. Error codes are
defined in quanser_errors.h
. A suitable error message
may be retrieved using
msg_get_error_message.
Error codes
QERR_HIL_READ_DIGITAL_BUFFER_NOT_SUPPORTED
This function is not supported by the board-specific HIL driver for this board type.
QERR_INVALID_CARD_HANDLE
An invalid card handle was passed as an argument. Once a card has been closed using hil_close the card handle is invalid.
QERR_TOO_MANY_DIGITAL_INPUT_CHANNELS
Too many digital input channels were specified.
QERR_INVALID_DIGITAL_INPUT_CHANNEL
One of the digital input channels that was specified is not a valid channel number. Channel numbers range from 0 to one less than the number of channels.
QERR_DRIVER_INCOMPATIBLE_WITH_BOARD_DLL
The board-specific HIL driver passed an invalid parameter to the operating system specific kernel-level driver for the board. The board-specific HIL driver is likely not compatible with the operating system specific kernel-level driver for the board. Make sure both are up-to-date and compatible versions.
QERR_INTERNAL_BUFFER_TOO_SMALL
The board-specific HIL driver used an internal buffer that was too small for the operating system specific kernel-level driver for the board. The board-specific HIL driver is likely not compatible with the operating system specific kernel-level driver for the board. Make sure both are up-to-date and compatible versions.
QERR_OUT_OF_REQUIRED_SYSTEM_RESOURCES
There are not enough system resources to perform the requested operation. Try rebooting, requesting fewer samples, or adding more memory to your machine.
QERR_OUT_OF_MEMORY
There is not enough memory to perform the operation.
Requirements
Include Files |
Libraries |
---|---|
hil.h |
hil.lib;quanser_runtime.lib;quanser_common.lib |
Examples
/* * Reads 5000 samples at 1 kHz from the first four digital input channels, using SYSTEM_CLOCK_1. */ t_uint32 channels[] = { 0, 1, 2, 3 }; t_double frequency = 1000; t_uint32 samples = 5000; static t_boolean buffer[5000][4]; t_error result = hil_read_digital_buffer(board, SYSTEM_CLOCK_1, frequency, samples, channels, ARRAY_LENGTH(channels), &buffer[0][0]);
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