OASIS (Open Analog Signals Input System)
WARNING!!! This page is under construction yet!!!
OASIS is intended to be the Open Hardware system for analog data
acquisition.
The industrial systems for analog data acquisition
are usually very expensive, but still lacking different features
needed for more sophisticated applications. A lot of them are
equipped with drivers for one only operating system.
Additionally sometimes the vendor supplied drivers do not utilise
all capabilities of the hardware, but the technical information
for writing of the own driver is not available, or an additional
price is charged for it (sometimes with NDA required).
To avoid all the above problems, I would like to start developing
of an Open Hardware analog data acquisition system.
This system is intended to be free in that sense, that all
the documentation for hardware is provided, and reproducing,
modifications and manufacturing is allowed for anybody without
any fee.
Additionally all drivers and firmware will be provided with sources,
(under the GPL or LGPL license) to
allow for their modification, improvement and adaptation for
different Operating Systems.
System components
- Device drivers
This part of the system depends on host computer's hardware
and its operating system. We would prefer two operating systems:
- DOS, because it is very simple operating sytem, which allows
the user program to obtain the full control over the computer's
hardware. It is important, that now exists the
free and open alternative
for DOS - Free DOS.
- Linux,
because it is free, high performance operating system
Of course drivers for other, free and commercial operating systems
are welcome.
- The transmission protocol
The open transmission protocol should allow to connect the system to
almost any desktop or laptop computer, working with any operating
system (preferrably Linux of course :-).
The transmission protocol should perform following task:
- uploading of the firmware to the system's controller
(optionally)
- configuring of data acquisition parameters
(sampling frequency and sampled channels)
- transmission of acquired data
- stopping of the data acquisition
Two transmission protocols are considered:
- The controller block
The controller block drives the analog signal multiplexer,
A/D converter, buffers the acquired data, and then transmits
them to the host computer.
It may be realized with almost any microcontroller, having sufficient
amount of RAM. (Maybe even with the EPLD?)
- The isolation block
For some applications (for example in medicine, or in industry) an
isolation between the host computer and measured signals is required.
Therefore in the system an optional isolating block is provided.
- The A/D converter
This module performs the sampling, and analog to digital conversion of
the signals.
In some applications, requiring low resolution AD-converters
(up to 10 bits), and not requiring the isolation block, it should
be possible to build the whole "intelligent ADC" with single
ADC equipped microcontroller (eg.
80C550,
80C552
or
PIC16F877
),
keeping its cost at very low level!
Wojciech Zabolotny
Last modified: Fri Aug 6 15:07:16 CEST 1999