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What chip? Inputs and rs232

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peetcool9

New Member
hello, i am trying to get something to read as many "switches" as posible. i was trying to use the parrallel port on a computer but that can only carry 5 inputs. is there a chip that can read just an on or off state on many pins? what would be another soution? i would just like it to serialy send status of all the pins to the comp to be decoded with software. i can handle the software stuff but the chip i am not sure what o use for this as there are soo many of them.
for now we can forget the fact that the chip has to be programmed. :wink:

thanks for the time. patrick
 

Nigel Goodwin

Super Moderator
Most Helpful Member
peetcool9 said:
hello, i am trying to get something to read as many "switches" as posible. i was trying to use the parrallel port on a computer but that can only carry 5 inputs. is there a chip that can read just an on or off state on many pins? what would be another soution? i would just like it to serialy send status of all the pins to the comp to be decoded with software. i can handle the software stuff but the chip i am not sure what o use for this as there are soo many of them.
for now we can forget the fact that the chip has to be programmed. :wink:

thanks for the time. patrick

You could always be it in hardware, but it's probably a lot easier to do it in software with a micro-controller. Personally I would use one of the PIC range, but that's because I use PIC's, and micro-controller would do.

How many switches do you need?, using an 18 pin 16F628, and using one of the pins for the RS232 output, you have 15 I/O pins free - so you could have 15 switches (using one per pin) or multiplex them and have 56 switches.
 

ivancho

New Member
You could use a Octal transiver Tri-state like the 74HC245.

Using the outputs of the parallel port, you can connect a whole bunch of this 74HC245 and control their enable line so that only one of them is enable at a time..... and you can ground the direction pin and read the outputs as you enable the lines.

Just another idea instead of the serial... although I would probably go serial for simplicity, efficiency and size :wink:

Ivancho
 

panic mode

Well-Known Member
When ever you need to controll a LOT of something, (switches, LEDs,...)
it's time to multiplex. For example to use 9 switches, sure you could use
9 inputs but if you multiplex them, you could use 3 outputs and 3 inputs
(3x3=9). You could also use 9 outputs and 1 input (9x1=9).
LPTs are not all the same but even so you should have couple of output
and input lines (8x5?). Do you think this is plenty?
 

TheAnimus

New Member
If your parport supports the 'newer' modes of data transfer, you should be able to have 13 inputs (without plexing).
 
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