4.3.3 - Analog Inputs

The IOTypes to retrieve a command/response analog input reading are:

LJ_ioGET_AIN       //Single-ended.  Negative channel is fixed as 0/15/199.
LJ_ioGET_AIN_DIFF  //Specify negative channel in x1.

Differential channels are adjacent even/odd pairs only, such as AIN2-AIN3. Thus the positive channel must be even and the negative channel must be +1. The Windows UD driver has different IOTypes for single-ended or differential reads, but the differential IOType can always be used as a negative channel (x1 parameter) of 0/15/199 equates to a single-ended reading.

The following are IOTypes used to configure the input range of a particular analog input channel:

LJ_ioPUT_AIN_RANGE    // Range and Gain are synonymous

In addition to specifying the channel number, the following range (i.e. gain) constants are passed in the value parameter when doing a request with the AIN range IOType:

LJ_rgBIP10V     // +/- 10V, i.e. Gain=x1
LJ_rgBIP1V      // +/- 1V, i.e. Gain=x10
LJ_rgBIPP1V     // +/- 0.1V, i.e. Gain=x100
LJ_rgBIPP01V    // +/- 0.01V, i.e. Gain=x1000

The following are special channels, used with the get/put config IOTypes, to configure parameters that apply to all analog inputs:

LJ_chAIN_RESOLUTION     //0=default, 1-8=high-speed ADC, 9-12=high-res ADC
LJ_chAIN_SETTLING_TIME  //0-9 where 0=Auto, see Section 5.2.5.2
LJ_chAIN_BINARY

Following is example pseudocode to read analog inputs:

//Configure all analog inputs for max resolution.  Like most
//settings, this will apply to all further measurements until
//the parameter is changed or the DLL unloaded.
AddRequest (lngHandle, LJ_ioPUT_CONFIG, LJ_chAIN_RESOLUTION, 12, 0, 0);

//Configure AIN1 for +/- 10 volt range.
AddRequest (lngHandle, LJ_ioPUT_AIN_RANGE, 1, LJ_rgBIP10V, 0, 0);

//Configure AIN2 for +/- 1 volt range.  This applies to any
//reading, single-ended or differential, where the positive
//channel is AIN2.
AddRequest (lngHandle, LJ_ioPUT_AIN_RANGE, 2, LJ_rgBIP1V, 0, 0);

//Request a single-ended read from AIN1.
AddRequest (lngHandle, LJ_ioGET_AIN, 1, 0, 0, 0);

//Request a differential read of AIN2-AIN3.
AddRequest (lngHandle, LJ_ioGET_AIN_DIFF, 2, 0, 3, 0);

//Request a single-ended read of AIN2.  Here we use the DIFF
//IOType, but pass x1=199 which does a single-ended measurement.
AddRequest (lngHandle, LJ_ioGET_AIN_DIFF, 2, 0, 199, 0);

//Execute the requests.
GoOne (lngHandle);

//Since multiple requests were made with the same IOType
//and Channel, and only x1 was different, GetFirst/GetNext
//must be used to retrieve the results.  The simple
//GetResult function does not use the x1 parameter and
//thus there is no way to specify which result is desired.
//Rather than specifying the IOType and Channel of the
//result to be read, the GetFirst/GetNext functions retrieve
//the results in order.  Normally, GetFirst/GetNext are best
//used in a loop, but here they are simply called in succession.

//Retrieve AIN1 voltage.  GetFirstResult returns the IOType,
//Channel, Value, x1, and UserData from the first request.
//In this example we are just retrieving the results in order
//and Value is the only parameter we need.
GetFirstResult (lngHandle, 0, 0, &dblValue, 0, 0);

//Get the AIN2-AIN3 voltage.
GetNextResult (lngHandle, 0, 0, &dblValue, 0, 0);

//Get the AIN2.
GetNextResult (lngHandle, 0, 0, &dblValue, 0, 0);