hil_write_buffer :: Quanser C Functions

navigation bar

hil_write_buffer

Writes the specified number of samples to the analog, PWM, digital and/or other channels at the indicated sampling rate.

Description

The hil_write_buffer function writes the specified number of samples to the output channels at the given sampling rate. The function does not return until the data has been written.

Warning 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 outputs must be configured as outputs using this function. Failure to configure the digital I/O may result in the hil_write_buffer function failing to write those outputs.

The interpretation of the PWM samples to be written depends upon the PWM mode. Typically the data is interpreted as a duty cycle, in which a magnitude of 0.0 denotes a 0% duty cycle and magnitude of 1.0 indicates a 100% duty cycle. The sign determines the polarity of the output for those boards supporting bidirectional PWM outputs. However, other PWM modes are possible with some boards. Refer to the hil_set_pwm_mode function for details.

Prototype

t_error 
hil_write_buffer(t_card card, t_clock clock, t_double frequency, t_uint32 num_samples,
                 const t_uint32  analog_channels[],  t_uint32 num_analog_channels,
                 const t_uint32  pwm_channels[],     t_uint32 num_pwm_channels,
                 const t_uint32  digital_channels[], t_uint32 num_digital_channels,
                 const t_uint32  other_channels[],   t_uint32 num_other_channels,
                 const t_double  analog_buffer[],
                 const t_double  pwm_buffer[],
                 const t_boolean digital_buffer[],
                 const t_double  other_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 write to the output channels. For example, if frequency is set to 1000, then the hil_write_buffer function will write all the selected channels every millisecond.

t_uint32 num_samples

The number of samples to collect. Each "sample" consists of all the output channels specified. For example, if frequency is set to 1000 and num_samples is set to 5000, then the hil_write_buffer function will return after 5 seconds with 5000 samples. If 3 channels in total have been selected, then the output buffer will contain 15,000 elements.

const t_uint32 [] analog_channels

An array containing the channel numbers of the analog outputs to which to write.

Select a board type from the list for board-specific details: .

If no analog channels are required then this parameter may be NULL. In this case, num_analog_channels must be zero.

t_uint32 num_analog_channels

The number of channels specified in the analog_channels array. This parameter may be zero.

const t_uint32 [] pwm_channels

An array containing the channel numbers of the PWM outputs to which to write.

Select a board type from the list for board-specific details: .

If no PWM channels are required then this parameter may be NULL. In this case, num_pwm_channels must be zero.

t_uint32 num_pwm_channels

The number of channels specified in the pwm_channels array. This parameter may be zero.

const t_uint32 [] digital_channels

An array containing the channel numbers of the digital outputs to which to write.

Select a board type from the list for board-specific details: .

If no digital channels are required then this parameter may be NULL. In this case, num_digital_channels must be zero.

t_uint32 num_digital_channels

The number of channels specified in the digital_channels array. This parameter may be zero.

const t_uint32 [] other_channels

An array containing the channel numbers of the other outputs to which to write.

Select a board type from the list for board-specific details: .

If no other channels are required then this parameter may be NULL. In this case, num_other_channels must be zero.

t_uint32 num_other_channels

The number of channels specified in the other_channels array. This parameter may be zero.

const t_double [] analog_buffer

An array containing the voltage values to write to the analog outputs. The array must contain num_analog_channels * num_samples elements. The array must be organized as a linear array of samples, with each sample consisting of a group of channels. For example, if analog output channels 0, 1 and 3 are being written, than the data must appear in the array as follows, where the numbers correspond to channel numbers:

...

This ordering is equivalent to defining the buffer as:

t_double buffer[num_samples][num_channels];

If the buffer is defined in this way then pass the buffer as the analog_buffer argument using the syntax: &buffer[0][0].

If no analog channels were specified then this parameter may be NULL.

const t_double [] pwm_buffer

An array containing the values to write to the PWM outputs. How these values are interpreted depends on the PWM mode. The PWM mode is configured using the hil_set_pwm_mode function. The array must contain num_pwm_channels * num_samples elements. The array must be organized as a linear array of samples, with each sample consisting of a group of channels. Refer to the analog_buffer parameter for an example.

If no PWM channels were specified then this parameter may be NULL.

const t_boolean [] digital_buffer

An array containing the binary values to write to the digital outputs. The array must contain num_digital_channels * num_samples elements. The array must be organized as a linear array of samples, with each sample consisting of a group of channels. Refer to the analog_buffer parameter for an example.

If no digital channels were specified then this parameter may be NULL.

const t_double [] other_buffer

An array containing the values to write to the other outputs. The array must contain num_other_channels * num_samples elements. The array must be organized as a linear array of samples, with each sample consisting of a group of channels. Refer to the analog_buffer parameter for an example.

If no other channels were specified then this parameter may be NULL.

Return value

The return value is the number of samples successfully written. 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_WRITE_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_MISSING_ANALOG_OUTPUTS

The analog_channels argument is NULL. If the number of channels is greater than zero then a channel vector must be provided.

QERR_MISSING_ANALOG_OUTPUT_BUFFER

The analog_buffer argument is NULL. If the number of channels is greater than zero then a buffer must be provided.

QERR_TOO_MANY_ANALOG_OUTPUT_CHANNELS

Too many analog output channels were specified.

QERR_INVALID_ANALOG_OUTPUT_CHANNEL

One of the analog output channels that was specified is not a valid channel number. Channel numbers range from 0 to one less than the number of channels.

QERR_MISSING_PWM_OUTPUTS

The pwm_channels argument is NULL. If the number of channels is greater than zero then a channel vector must be provided.

QERR_MISSING_PWM_OUTPUT_BUFFER

The pwm_buffer argument is NULL. If the number of channels is greater than zero then a buffer must be provided.

QERR_TOO_MANY_PWM_OUTPUT_CHANNELS

Too many PWM output channels were specified.

QERR_INVALID_PWM_OUTPUT_CHANNEL

One of the PWM output channels that was specified is not a valid channel number. Channel numbers range from 0 to one less than the number of channels.

QERR_HARDWARE_CLOCK_IN_USE

One of the PWM output channels is based on a hardware clock that is already in use for another operation and the board-specific HIL driver for this board does not permit sharing of the hardware clock.

QERR_WRONG_CLOCK_MODE

One of the PWM output channels is based on a hardware clock that is in the wrong mode for this operation. Use the hil_set_clock_mode function to change modes.

QERR_MISSING_DIGITAL_OUTPUTS

The digital_channels argument is NULL. If the number of channels is greater than zero then a channel vector must be provided.

QERR_MISSING_DIGITAL_OUTPUT_BUFFER

The digital_buffer argument is NULL. If the number of channels is greater than zero then a buffer must be provided.

QERR_TOO_MANY_DIGITAL_OUTPUT_CHANNELS

Too many digital output channels were specified.

QERR_INVALID_DIGITAL_OUTPUT_CHANNEL

One of the digital output channels that was specified is not a valid channel number. Channel numbers range from 0 to one less than the number of channels.

QERR_MISSING_OTHER_OUTPUTS

The other_channels argument is NULL. If the number of channels is greater than zero then a channel vector must be provided.

QERR_MISSING_OTHER_OUTPUT_BUFFER

The other_buffer argument is NULL. If the number of channels is greater than zero then a buffer must be provided.

QERR_TOO_MANY_OTHER_OUTPUT_CHANNELS

Too many other output channels were specified.

QERR_INVALID_OTHER_OUTPUT_CHANNEL

One of the other output 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


/*
* Write 5000 samples at 1 kHz to two analog output channels, two PWM output channels
* and four digital output channels, using SYSTEM_CLOCK_1.
*/

t_double frequency = 1000;
t_uint32 samples   = 5000;

t_uint32 analog_channels[]  = { 0, 1 };
t_uint32 pwm_channels[]     = { 0, 1 };
t_uint32 digital_channels[] = { 0, 1, 2, 3 };
t_error result;
int i, j;

static t_double  analog_buffer[5000][2];
static t_double  pwm_buffer[5000][2];
static t_boolean digital_buffer[5000][4];

for (i=0; i < samples; i++) {
    double time = i / frequency;
    for (j=0; j < ARRAY_LENGTH(analog_channels); j++)
        analog_buffer[i][j] = (j + 7.0) * sin(2*M_PI*time);
    for (j=0; j < ARRAY_LENGTH(pwm_channels); j++)
        pwm_buffer[i][j] = sin(2*M_PI*time);
    for (j=0; j < ARRAY_LENGTH(digital_channels); j++)
        digital_buffer[i][j] = (i % (j + 2)) >= (j + 2)/2;
}

result = hil_write_buffer(board, SYSTEM_CLOCK_1, frequency, samples
                        , analog_channels,  ARRAY_LENGTH(analog_channels)
                        , pwm_channels,     ARRAY_LENGTH(pwm_channels)
                        , digital_channels, ARRAY_LENGTH(digital_channels)
                        , NULL,             0   /* no other channels */
                        , analog_buffer
                        , pwm_buffer
                        , digital_buffer
                        , NULL                  /* no other channels */
                        );

navigation bar