looking for a middle man

Hi all,

Just came up with a devastating realization . My all-too-expensive LM629's , encoders steering setup will not work through the parallel port. The number or i/o lines to "talk" to the 629's aren't enough . I am just thinking aloud . Could I use an intermediate micro-controller to recieve commands from the PC ( 4 bits ), 16 commands are enough and then the micro-controller to output hex instructions for the 629 to understand . Since my position , vel,accn co-efficients are going to be constant ( the motor shaft moves through a fixed pos,at const vel,accn
[10 degrees , 500 rev/s and 0.1 rad/ s/s]
for every 1v change in the joystick pot) . Why then a PC ? for one - I can display a virtual steering and other input data such a joystick pos . But the important reason is that joystick inputs are read by the computer.


Any other suggestions on how this could be implemented

Thanks

A micro should work for this app. The serial port is usualy used for PC to micro communication rather than the Parallel port.

If you want a simple solution J.R. Kerr sells a PIC with a PID controller pre-programed in. You just send it commands. Its designed to talk to the serial port.

One common trick to increase the number of I/O lines is to use data latches.
1 octal latch : 8 outputs from 9 inputs
2 octal latches : 16 outputs from 10 inputs
3 octal latches : 24 outputs from 11 inputs
4 octal latches : 32 outputs from 11 inputs
and so on.

How many do you need?

if you want to use an ISA bus PC, my circuit can/will give you 8 input bits and as it currently configured 4 ,individually controlled outputs..

oh the last page has the circuit drawn with eagle..

The PC-s parallel port [PP] has three busses:

Data bus output 8bits (D0-D7) Adr= BASE
Sense bus input 5 bits (S3-S7) Adr=BASE+1
control bus output 4 bits (C0-C3) adr=BASE+2

S7,C0,C1 and C3 are inverted.
Under DOS the BASE can be found at 0x0000:0x0408 and ....409
(Lsb-Msb)

I would use C for address and D for data out, S for data in.