hil_read_write_buffer :: Quanser C Functions

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hil_read_write_buffer

Reads the specified number of samples from the analog, encoder, digital and/or other input channels and writes the specified number of samples to the analog, PWM, digital and/or other output channels at the indicated sampling rate.

Description

The hil_read_write_buffer function reads the specified number of samples from the input channels and writes to the specified output channels at the given sampling rate in a single function call. Each sampling instant, the write operation occurs immediately following the read operation. Since the read-write operation occurs at the lowest level the read and write occur virtually concurrently. The function does not return until all the data has been read and written. This function is particularly useful for system identification since the read and write operations are synchronized. In particular, the value read in one sampling instant is the result of the write operation in the previous sampling instant. See the Buffered I/O overview for more details.

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 inputs or outputs must be configured accordingly using this function. Failure to configure the digital I/O may result in the hil_read_write_buffer function failing to read or write the digital I/O as expected.

The interpretation of the PWM data 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_read_write_buffer(t_card card, t_clock clock, t_double frequency, t_uint32 num_samples,
                      const t_uint32 analog_input_channels[],  t_uint32 num_analog_input_channels,
                      const t_uint32 encoder_input_channels[], t_uint32 num_encoder_input_channels,
                      const t_uint32 digital_input_lines[],    t_uint32 num_digital_input_lines,
                      const t_uint32 other_input_channels[],   t_uint32 num_other_input_channels,
  
                      const t_uint32 analog_output_channels[], t_uint32 num_analog_output_channels,
                      const t_uint32 pwm_output_channels[],    t_uint32 num_pwm_output_channels,
                      const t_uint32 digital_output_lines[],   t_uint32 num_digital_output_lines,
                      const t_uint32 other_output_channels[],  t_uint32 num_other_output_channels,
  
                      t_double  analog_input_buffer[],
                      t_int32   encoder_input_buffer[],
                      t_boolean digital_input_buffer[],
                      t_double  other_input_buffer[],
  
                      const t_double  analog_output_buffer[],
                      const t_double  pwm_output_buffer[],
                      const t_boolean digital_output_buffer[],
                      const t_double  other_output_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 read from the input channels and write to the output channels. For example, if frequency is set to 1000, then the hil_read_write_buffer function will read all the input channels and write all the output channels every millisecond.

t_uint32 num_samples

The number of samples to process. Each "sample" consists of all the input channels and all the output channel specified. For example, if frequency is set to 1000 and num_samples is set to 5000, then the hil_read_write_buffer function will return after 5 seconds, having read 5000 samples and written 5000 samples. If 3 input channels have been selected, then the input buffer will contain 15,000 elements. If 2 output channels have been selected, then the output buffer must contain 10,000 elements.

const t_uint32 [] analog_input_channels

An array containing the channel numbers of the analog inputs to be read.

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

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

t_uint32 num_analog_input_channels

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

const t_uint32 [] encoder_input_channels

An array containing the channel numbers of the encoder inputs to be read.

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

If no encoder input channels are required then this parameter may be NULL. In this case, num_encoder_input_channels must be zero.

t_uint32 num_encoder_input_channels

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

const t_uint32 [] digital_input_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: .

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

t_uint32 num_digital_input_channels

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

const t_uint32 [] other_input_channels

An array containing the channel numbers of the other inputs to be read.

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

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

t_uint32 num_other_input_channels

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

const t_uint32 [] analog_output_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 output channels are required then this parameter may be NULL. In this case, num_analog_output_channels must be zero.

t_uint32 num_analog_output_channels

The number of channels specified in the analog_output_channels array.

const t_uint32 [] pwm_output_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 output channels are required then this parameter may be NULL. In this case, num_pwm_output_channels must be zero.

t_uint32 num_pwm_output_channels

The number of channels specified in the pwm_output_channels array.

const t_uint32 [] digital_output_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 output channels are required then this parameter may be NULL. In this case, num_digital_output_channels must be zero.

t_uint32 num_digital_output_channels

The number of channels specified in the digital_output_channels array.

const t_uint32 [] other_output_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 output channels are required then this parameter may be NULL. In this case, num_other_output_channels must be zero.

t_uint32 num_other_output_channels

The number of channels specified in the other_output_channels array.

t_double [] analog_input_buffer

An array for receiving the voltage values read from the analog inputs. The array must contain num_analog_input_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 analog 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:

...

This ordering is equivalent to defining the buffer as:

t_double 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].

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

t_int32 [] encoder_input_buffer

An array for receiving the counter values read from the encoder inputs. The array must contain num_encoder_input_channels * num_samples elements. The array is organized as a linear array of samples, with each sample consisting of a group of channels. Refer to the analog_input_buffer parameter for an example.

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

t_boolean [] digital_input_buffer

An array for receiving the binary values read from the digital inputs. The array must contain num_digital_input_channels * num_samples elements. The array is organized as a linear array of samples, with each sample consisting of a group of channels. Refer to the analog_input_buffer parameter for an example.

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

t_double [] other_input_buffer

An array for receiving the values read from the other inputs. The array must contain num_other_input_channels * num_samples elements. The array is organized as a linear array of samples, with each sample consisting of a group of channels. Refer to the analog_input_buffer parameter for an example.

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

const t_double [] analog_output_buffer

An array containing the voltage values to write to the analog outputs. The array must contain num_analog_output_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_input_buffer parameter for an example.

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

const t_double [] pwm_output_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_output_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_input_buffer parameter for an example.

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

const t_boolean [] digital_output_buffer

An array containing the binary values to write to the digital outputs. The array must contain num_digital_output_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_input_buffer parameter for an example.

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

const t_double [] other_output_buffer

An array containing the values to write to the other outputs. The array must contain num_other_output_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_input_buffer parameter for an example.

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

Return value

The return value is the number of samples successfully read and 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_READ_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_HARDWARE_CLOCK_IN_USE

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

QERR_TOO_MANY_ANALOG_INPUT_CHANNELS

Too many analog input channels were specified.

QERR_INVALID_ANALOG_INPUT_CHANNEL

One of the analog 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_ANALOG_RESOURCE_IN_USE

The analog-to-digital converter on the HIL board is currently in use by another operation.

QERR_TOO_MANY_ENCODER_INPUT_CHANNELS

Too many encoder input channels were specified.

QERR_INVALID_ENCODER_INPUT_CHANNEL

One of the encoder 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_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_TOO_MANY_OTHER_INPUT_CHANNELS

Too many other input channels were specified.

QERR_INVALID_OTHER_INPUT_CHANNEL

One of the other 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_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_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_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_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_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


/*
* Reads 5000 samples at 1 kHz from the first two analog input channels,
* the first two encoder input channels and digital channels 6 and 7
* and writes at the same time to the first two analog output channels and
* the first three digital channels, using SYSTEM_CLOCK_1.
*/

t_double frequency = 1000;
t_uint32 samples   = 5000;
t_error result;
int i, j;

t_uint32  analog_input_channels[]  = { 0, 1 };
t_uint32  encoder_input_channels[] = { 0, 1 };
t_uint32  digital_input_channels[] = { 6, 7 };

static t_double  analog_input_buffer[5000][2];
static t_int32   encoder_input_buffer[5000][2];
static t_boolean digital_input_buffer[5000][2];

t_uint32  analog_output_channels[]  = { 0, 1 };
t_uint32  digital_output_channels[] = { 0, 1, 2 };

static t_double  analog_output_buffer[5000][2];
static t_boolean digital_output_buffer[5000][3];

for (i=0; i < samples; i++) {
    double time = i / frequency;
    for (j=0; j < ARRAY_LENGTH(analog_output_channels); j++)
        analog_output_buffer[i][j] = (j + 7.0) * sin(2*M_PI*time);
    for (j=0; j < ARRAY_LENGTH(digital_output_channels); j++)
        digital_output_buffer[i][j] = (i % (j + 2)) >= (j + 2)/2;
}

result = hil_read_write_buffer(board, SYSTEM_CLOCK_1, frequency, samples
    , analog_input_channels,   ARRAY_LENGTH(analog_input_channels)
    , encoder_input_channels,  ARRAY_LENGTH(encoder_input_channels)
    , digital_input_channels,  ARRAY_LENGTH(digital_input_channels)
    , NULL,                    0
    , analog_output_channels,  ARRAY_LENGTH(analog_output_channels)
    , NULL,                    0
    , digital_output_channels, ARRAY_LENGTH(digital_output_channels)
    , NULL,                    0
    , &analog_input_buffer[0][0]
    , &encoder_input_buffer[0][0]
    , &digital_input_buffer[0][0]
    , NULL
    , &analog_output_buffer[0][0]
    , NULL
    , &digital_output_buffer[0][0]
    , NULL
);

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