Actuator API

The Actuator API encompasses the needed software to drive both the Digital-to-Analog Converter (DAC) and the physical device which it drives. The advantage this approach provides is that most programming to be done with a user's system can be done in nature engineering units rather than abstract volts or hex numbers. However, there are instances where a lower level treatment of these devices are required. In these cases, this API provides the ability to directly access the DAC's.

Example Use


In the following example, an 8 channel card is initialized.  Each DAC
is driving a servo amp.  Finally, the channel #0 amp is commanded to
1.5 Amps.

/* initialize actuators */
int numDacChannels, i;

numDacChannels = 8;
setNumDacs (8);
for (i = 0; i < numDacChannels; i++)
{
   
/* 12-bit, 10V max, bipolar, offset device */
   
initDac (i, 1, 0, 12, 10.0);
   
/* servo amp with a 0.0-5.0V input and +/-2.0Amps output */
   
initAct (i, 0.0, -2.0, 5.0, 2.0);
}
/* command the servoamp on channel #0 to 1.5Amps */
setActuator (0, 1.5);

getDacNumBits()
initAct()
initDac()
isDacBipolar()
isDacTwosComplement()
setActuator()
setActuatorMaximum()
setActuatorMinimum()
setDac()
setDacBipolar()
setDacHex()
setDacNumBits()
setDacReference()
setDacTwosComplement()
setNumDacs()
updateAll()
updateDac()
updateTotal()

getDacNumBits

unsigned int getDacNumBits (unsigned int channel);

Get the number of bits of resolution for a channel.

Parameters: channel - channel number of the associated DAC.
Returns: Resolution of the DAC channel in bits.

getNumDacs

unsigned int getNumDacs ()

Get the number of channels of DAC's.

Returns: Number of the DAC channels.

initAct

void initAct (unsigned int channel, float dacMin, float actMin, 
	      float dacMax, float actMax)

Initializes an actuator attached to a given DAC channel. The initialization includes setting both the maximum and minimum points which, with the basic DAC configuration, are used to establish the relationship between the physical units and the hex value used to command the DAC (see setActuator).

Parameters: channel - channel number of the DAC to set.; dacMin - minimum voltage for the DAC to command.; actMin - minimum physical value which corresponds to the minimum DAC voltage.; dacMax - maximum voltage for the DAC to command.; actMax - maximum physical value which corresponds to the maximum DAC voltage.

initDac

void initDac (unsigned int channel, int isBipolar, 
	      int isTwosComplement, unsigned int numBits,
	      float referenceVal)

Initializes a DAC channel with the device attributes.

Parameters: channel - channel number of the DAC to set.; isBipolar - set to 1 if bipolar or 0 if DAC is an unipolar type device.; isFullGain - set to 1 if full gain or 0 if DAC is to be configured to half gain.; isTwosComplement - set to 1 if two's complement is used or 0 if offset representation is used for DAC numbers.; numBits - number of bits resolution.; referenceVal - reference voltage of the DAC. Note, different devices have different rules for relating their reference to their range. This API uses the convention that the maximum voltage is one bit less than the reference voltage.

isDacBipolar

unsigned int isDacBipolar (unsigned int channel);

Returns the polarity setting of the DAC.

Returns: 0 - unipolar, 1 - bipolar.

isDacFullGain

unsigned int isDacFullGain (unsigned int channel);

Returns the gain setting of the DAC.

Returns: 0 - half gain, 1 - full gain.

isDacTwosComplement

unsigned int isDacTwosComplement (unsigned int channel);

Returns the number format setting of the DAC.

Returns: 0 - offset format, 1 - two's complement format.

setActuator

void setActuator (unsigned int channel, float value);

Sets the actuator, connected to a DAC channel, to a physical value. If the requested value exceeds the limits established, the limit is used instead.

Parameters: channel - channel number of the associated DAC to set; value - command to be set in the previously established physical units.

setActuatorMaximum

void setActuatorMaximum (unsigned int channel, float dacValue,
			 float actuatorValue);

Sets the maximum physical level and the associated DAC voltage command for a given channel.

Parameters: *channel - channel number of the DAC to set; dacValue - maximum voltage for the DAC to command (see setActuator); actuatorValue - maximum physical value which corresponds to the maximum DAC voltage.

setActuatorMinimum

void setActuatorMinimum (unsigned int channel, float dacValue,
			 float actuatorValue);

Sets the minimum physical level and the associated DAC voltage command for a given channel.

Parameters: channel - channel number of the DAC to set; dacValue - minimum voltage for the DAC to command (see setActuator); actuatorValue - minimum physical value which corresponds to the minimum DAC voltage.

setDac

void setDac (unsigned int channel, float value);

setDacBipolar

void setDacBipolar (unsigned int channel, int isBipolar);

setDacBipolar

void setDacBipolar (unsigned int channel, int isBipolar);

setDacFullGain

void setDacFullGain (unsigned int channel, int isBipolar);

setDacHex

void setDacHex (unsigned int channel, unsigned int value);

setDacNumBits

void setDacNumBits (unsigned int channel, unsigned int numBits);

setDacReference

void setDacReference (unsigned int noChannels, float value);

setDacTwosComplement

void setDacTwosComplement (unsigned int channel, 
                           int isTwosComplement);

setNumDacs

      void setNumDacs (unsigned int noChannels);

Set the number of channels of DAC's.

Returns: 0 - successful.; -1 - unsuccessful, memory was not allocated.

updateAll

void updateAll();

Updates all parameters and configurations for all DAC/actuators currently declared.

updateDac

void updateDac (unsigned int channel);

Updates the DAC-specific parameters and configurations for DAC currently declared.

Parameters: channel - channel number of the DAC to update.

updateTotal

unsigned int updateTotal (unsigned int channel);

Updates all parameters and configurations for DAC/actuator currently declared.

Parameters: channel - channel number of the DAC to update.

extern unsigned int ActLimitError; extern unsigned int DacLimitError; extern unsigned int safeDacHex;

Last modified: Thu Jul 22 07:02:34 Eastern Daylight Time 1999