[raduradu]

Hello guys,

I'm pretty new at this thing called CNC but i have a big problem

one input pin ...11 to be exact is in a different than all the others ...meaning it says i'm allays connected to GND (it's the port where i put a home switch on my machine) the one indicated by the manufacturer of my board ....last night i was playing with limit switches and they all worked fine (checked by mach3 diagnostics page )...today ...bam ...that pin is working vice verso than the others.

i connect pin 11 to gnd ...nothing happens ...no blinking led on mach3 screen ...change state to actve hi/low ...i juct cant get it to work, it-s like he dose not whant to take any signal ...can you give me a suggestion????


P.S. i forgot to mention that all the time the controller board was removed from the cable and the state of the input pin 11 did not changed .

[cngbrick]

I'm not familiar with your particular setup but I have encountered a situation where a parallel port needed pull up resistors to ensure the inputs where reading high when the input signals were disconnected.

For a pull up resistor, you can place a 3300 ohm resistor between your signal pin (11) and +5V. If you are not reading a "1" with the pull up resistor then you may have a faulty parallel port (they are quite fragile).

Hope this helps.
RT

[BBMNet]

The following GWBASIC program can be run to read your port. It assumes that the port configuration is standard setting the main port to address 888 (378H). The input port is 889 and the output port is 890. I personally use FreeDOS and suggest using it.

The signals and the associated pins can be found googling a little for a parallel port.

10 CLS
20 R$=INKEY$
30 IF R$=CHR$(27) GOTO 80
40 D%=INP(889) AND &HF8
50 LOCATE 1, 1
60 PRINT D%
70 GOTO 20
80 SYSTEM

This program clears the screen then prints at the upper left side a number reflecting changes in any of the five input lines. Remember that we are talking TTL levels, that is no lower than 0 volts and no higher than five volts or the port might get damaged. Also, bit <7> is reversed. This is the bit you are talking about. You should check if the actual status is not software reversed by your current program.

To end the program jusp press <ESC>.

I run similar programs to confirm the health of my ports which I use to control diverse machines. I would suggest to build a small board to try the whole port, that is the main 8 bits (which can be bidirectional) the 5 input bits and the 4 output bits.

Note: the main 8 bits are set for input if bit<5> on port 890 is set to 1 but it is also dependant on the port mode selected in the configuration table of the BIOS.

I hope this can be of help or at least not confuse you more.

[raduradu]

thx for the reply, I've got around a new mother board in the mean time the problem did not persist, the old one had also some bad capacitors and i was lazy to replace them and i just bought a new one ...for like 30 $. if i get to fix that board i'll make a control station for a small cnc machine for a friend and he'll have to buy a parallel card or mix the signals for the probe with one one the home switch (test it, it works)