Table of Contents
Analog I/O Wildcard User Guide
A package of pre-coded device driver functions is provided to make it easy to use the Analog I/O Wildcard. This code is available as a pre-compiled “kernel extension” library to C and Forth programmers.
Overview of the Software Device Driver Functions
The Analog I/O Wildcard driver code makes it easy to initialize the A/D and DAC, acquire 16-bit samples from the A/D, and write 12-bit values to the DAC. The following sections describe the functions that initialize the A/D and DAC, read from the A/D inputs, and write to the DAC outputs.
Most of the functions accept as input parameters the channel number and the Analog I/O Wildcard Number (0 through 7). Be sure the module number passed to the software functions correspond to the hardware jumper settings as described in Table 1-2 above.
Initializing the Analog I/O Software Drivers
Use Init_Analog_IO to initialize the software drivers for the DAC and A/D, set the reference voltage of the DAC, and output 0 volts to all DAC channels. Init_Analog_IO must be called before attempting to read a value from the A/D or write a value to the DAC. The constants INT_2V_DAC12, INT_1V_DAC12, and EXT_DAC12, specify one of the three different reference voltage options for the DAC when passed to Init_Analog_IO. The following section provides more information about the DAC reference voltage options.
The Analog I/O Wildcard has eight 12-bit DAC outputs. Each DAC accepts a number between 0 and 4095 that we’ll designate as N, and outputs a voltage given by Equation 1-1.
There are three different options for Vref:
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