Multicore Cable Tester

[Ian Helie]

Hi,

I am designing a multicore (19 cores) cable tester, I need 19 outputs routed
back into 19 inputs. I was going to use a PIC (16F877) connected to 2 x 8255
multi i/o chips to give me 19 outputs and 19 inputs.

Has anybody got any ideas on a better way of doing this as the 8255 chip is
outdated.

Can anybody give me the numbers of other multi i/o chips that are up-to-date
or have more i/o lines.

Any help will be appreciated.

Yours Hopefully,

Ian Helie.
GM7VHQ

 

[Activ8]

Hi,

I am designing a multicore (19 cores) cable tester, I need 19 outputs routed
back into 19 inputs. I was going to use a PIC (16F877) connected to 2 x 8255
multi i/o chips to give me 19 outputs and 19 inputs.

Has anybody got any ideas on a better way of doing this as the 8255 chip is
outdated.

No doubt. Doesn't that one go back to the 8080 days?

Can anybody give me the numbers of other multi i/o chips that are up-to-date
or have more i/o lines.

Any help will be appreciated.

Yours Hopefully,

Ian Helie.
GM7VHQ

For continuity only? Did they stop making mux/demux chips? Look at a
databook starting with say, 74HC151. An HC154 or 4514 will take care
of 16 of your 19 in the transmitter. Activate a line and scan the
other side for one and only one active line.

Er... that PIC has enough i/o to do this singlehandedly.

 

[nospam]

Hi,

I am designing a multicore (19 cores) cable tester, I need 19 outputs routed
back into 19 inputs. I was going to use a PIC (16F877) connected to 2 x 8255
multi i/o chips to give me 19 outputs and 19 inputs.

Has anybody got any ideas on a better way of doing this as the 8255 chip is
outdated.

For a specific cable connect the 19 conductors in series with 18 equal
value resistors R. Then make sure you measure 18R between the two ends.

This will detect all opens, all shorts, and the majority of miswires. Use
low value resistors if you are worried about high resistance cable
connections, use high value resistors and a high test voltage if you are
worried about leakage and break down.

 

[Ken Smith]

For a specific cable connect the 19 conductors in series with 18 equal
value resistors R. Then make sure you measure 18R between the two ends.

Better yet:

If you use 1% resistors, it is not too hard to make a circuit that gets
opens, shorts and swapped connections. You apply, lets say, 10V across
the whole string and measure across the last resistor. The trick is that
you have resistors in a long series chain and resistors from each point to
ground. The resistors are all different values. Swapping connections
changes the order and hence the voltage on the resistors to ground.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Hi,

I am designing a multicore (19 cores) cable tester, I need 19 outputs routed
back into 19 inputs. I was going to use a PIC (16F877) connected to 2 x 8255
multi i/o chips to give me 19 outputs and 19 inputs.

Has anybody got any ideas on a better way of doing this as the 8255 chip is
outdated.

Can anybody give me the numbers of other multi i/o chips that are up-to-date
or have more i/o lines.

Any help will be appreciated.

Yours Hopefully,

Ian Helie.
GM7VHQ

You can also do it analog. Decode with a 3 to 8 or 4 to 16 decoder, and
then gate a 4051 analog muxer chip.