24 Channel multiplexer witrh Parallel port

[maxi]

Hi,
ive found on web many project of datalogger controlled by parallel port
a A/D converter and a 16 multiplexer .
The limit see to be the only 4 bit of the parallel port that can
control a 16 channel only MUX(4067)

Somebody has some idea for having 24 channel read via Parallel port?


Tyhanks in avance.

 

[Rich Grise]

Hi,
ive found on web many project of datalogger controlled by parallel port
a A/D converter and a 16 multiplexer .
The limit see to be the only 4 bit of the parallel port that can
control a 16 channel only MUX(4067)

Somebody has some idea for having 24 channel read via Parallel port?

Sure. Instead of trying to select a port by way of the command
bits, just use them to control an "address" and a "data" port. Do
two writes (well, four, actually) - toggle one of the control bits
to indicate "address," and strobe out a number from 00h-FFh. That's
256 ports. Having selected a port, toggle the control bit to "data",
and send the data. (or turn the port around and read the data, if it's
one o' them newfangled bidirectionsl parallel port thingies. ;-) )

Using the resultant 8 bits of "address" to actually address your 256
ports is, as usual, left as an exercise for the student. ;-D

Good Luck!
Rich