Parallel port i/o

[Fred Mill]

I have had some interest in this, so I thought I=92d post a more detailed=
=20
spec. to the list. Sorry for the length. This is the first cut of the=20
hardware spec for the EPPIO board and covers the functions I need for my=20
current project.  If anyone else is interested in boards, please let me=20
know. As I am in the early stages of the project, I=92m open to adding=20
hardware to make this a more useful general purpose board, as long as=20
the =91feature creep=92 doesn=92t get out of hand.J

I am planning to do this i/o board with discrete logic. It has a lot of=20
i/o pins, and I don=92t have the time or development system to use a=20
microcontroller. From the PC software perspective, it will look like an=20
address port and a data port. Write to the address port to select an i/o=20
channel, then read or write the data port.

Board specs:
5 Channels of 8 bit counter/timer.=20
Jumper for counter or timer selection.
Xtal control clock.
Jumper for clock frequency.
Signal conditioning for magnetic sensor. (flywheel)
(If someone knows of a good programmable=20
counter timer chip please let me know.)

3 channels of latched 8 bit digital out.
Outputs will have high current drivers to drive air control solenoids.=20
(12-24V,1-1.5A), or could be jumpered for 0-5V.
Depending on what drivers I use, I would like to have current control
and short circuit protection.=20

3 Channels of 8 bit digital input 0-5V.=20
Board space for optional pull-up / pull-down resistors.
Inputs will not be latched.
Schmitt trigger inputs.
Inputs will have some sort of ESD protection and noise filtering.=20

16 channels of 8 bit A/D.
Signal conditioning for:
	Thermocouple=20
	Thermistor or RTD
	Map sensor (onboard or external)
	2 axis accelerometer (onboard or external)
	Strain gauge / low level input
	0-5V input

Address decoding and handshaking for parallel port.
Watchdog timer?
Power on reset.
Regulated power supply operating from 12V.
Reference voltage for sensors.
Breadboard area.
Jumper area for I/O configuration.=20
Address switch or jumper to allow multiple boards to run off same port.
Board will be size and shape to fit some type of commercially available=20
metal enclosure.=20

As to cost, I don=92t really know yet. Looks like the chip count could go=
=20
to 35+. I would like to do this on a double sided board if I can. Cost=20
of boards will also depend on number ordered. I will do what I can to=20
keep the board and chip cost down. If you don=92t need all the hardware,=20
you can stuff only the functionality you need.

Fred Mill

millfm at wolfenet.com