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toolman1:

Your response to AndyB is probably not very useful.

What brand of computer and how new? Recent Dell's have apparently gone from using a source of about +/-12 V to +/- 5 V for the RS232 drivers.

You need to be more precise in defining the set up and how you made the measurements. Do have any detailed knowledge on how RS232 and asynchronous communication work?

Your statement of 5 V DC on pin 3 and 7 is somewhat meaningless. Does this mean both pins 3 and 7 were at 5 V relative to an undefined point, or did you mean to say that pin 3 was +5 V DC relative to pin 7? This is a quite unexpected voltage, being at +5, whether data is being sent or at rest. Was this measurement at the CNC connector end of the cable with it unconnected from the CNC and only the voltmeter as a load? Or while connected to the CNC?

You need to know that at the Fadal CNC pin 7 is common, probably connected directly to machine chassis. On HAAS pin 7 to chassis is thru a 100 ohm resistor. With nothing plugged into the Fadal 25 pin connector and no data being output you should expect the voltage from pin 3, RxD, relative to pin 7 to be close to zero volts. I just checked a computer and read +0.09 V. Pin 2, TxD, relative to pin 7 should read in the range of -5 to -12 V. The value will be near whatever is internally used for the source voltage for the RS232 driver. Note you can probably use the threaded post of the 25 pin connector on the CNC for your common reference. Not so the screw on the cable connector in most cases. On the machine if pin 7 is connected to chassis you should read 0 volts between the post and pin 7.

To do the next test may require 4 and 5 jumpered, and separately 6, 8, and 20. And it may depend upon Fadal allowing you to send data without some sort of software handshake. Measure the voltage on pin 2 relative to pin 7. Before sending data this should be the aforesaid -5 to -12 V. When sending data out this should jump around within about +/- 1 V.

If this test works, then you are outputting some sort of data.

Next you connect the cable between the computer and the CNC, run Microsoft Hyper Terminal and send data to the PC and see if there is any readable data or even garbage. The result here determines what you do next.

In other words there is a logical procedure that you can use to troubleshoot your system. This is in contrast to taking a big black box and trying many many combinations to try to determine the problem. You need to know that some of the hardware and some of the software at the two ends can communicate before you start looking for other hardware or software problems.

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