The ad driver provides an interface to the Data Translation A/D converter. This is not a real-time driver, but merely allows the user process to sample the board's channels one at a time. Each minor device selects a different A/D board.
The driver communicates to a user process by means of
ioctl(2)s.
The
AD_CHAN
ioctl(2)
selects which channel of the board to read.
For example,
chan = 5;
ioctl(fd, AD_CHAN, &chan);
selects channel 5.
The
AD_READ
ioctl(2)
actually reads the data and returns it to the user
process.
An example is
ioctl(fd, AD_READ, &data);
/dev/ad