hil_read_encoder_write_pwm :: Quanser C Functions

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hil_read_encoder_write_pwm

Reads from encoder inputs and writes to PWM outputs immediately.

Description

The hil_read_encoder_write_pwm function reads from the specified encoder input channels and writes to the specified PWM output channels in a single function call. 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 the data has been read and written.

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_encoder_write_pwm(t_card card, 
                           const t_uint32 encoder_input_channels[], t_uint32 num_encoder_input_channels, 
                           const t_uint32 pwm_output_channels[],    t_uint32 num_pwm_output_channels, 
                           t_int32        encoder_input_buffer[],
                           const t_double pwm_output_buffer[]);

Parameters

t_card card

A handle to the board, as returned by hil_open

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: .

t_uint32 num_encoder_input_channels

The number of channels specified in the encoder_input_channels array.

const t_uint32 [] pwm_output_channels

An array containing the channel numbers of the PWM outputs to be written.

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

t_uint32 num_pwm_output_channels

The number of channels specified in the pwm_output_channels array.

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 elements. Each element in the returned encoder_input_buffer array will correspond to the same element in the encoder_input_channels array.

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 elements. Each element in the pwm_output_buffer array correspondsis to the same element in the pwm_output_channels array.

Return value

The return value is 0 if the I/O operation is performed successfully. 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_ENCODER_WRITE_PWM_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_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_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_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.

Requirements

Include Files	Libraries
hil.h	hil.lib;quanser_runtime.lib;quanser_common.lib

Examples


/*
* Read the first four encoder input channels and writes
* to the first two PWM output channels.
*/

t_uint32 input_channels[]  = { 0, 1, 2, 3 };
t_double input_buffer[4];

t_uint32 output_channels[] = { 0, 1 };
t_double output_buffer[]   = { 0.7, 0.3 };

t_error result = hil_read_encoder_write_pwm(board
    , input_channels,  ARRAY_LENGTH(input_channels)
    , output_channels, ARRAY_LENGTH(output_channels)
    , input_buffer
    , output_buffer
);

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