Losing Data on RS-232 transfer, Yasnac MX-1

[gearsoup]

I've got an '82 Matsuura MC-500 in my garage. I've got it wired up with an RS232 cable (actual serial port on my PC). I will often find that it is missing end of blocks, or even dropping a J0. I read that running it too close to wiring, or fluorescent lights can cause this, so I rerouted the wire as best as I could. Still does it. Also, on long files, it will just drop the last half of it, it seems.

Baud rate was originally set to 1200. It did it then. So, I jumped it up to 2400, still did it.......

[dcoupar]

Is your cable shielded? Is the shield connected to pin 1 of the CNC end?

[angelw]

Originally Posted by gearsoup I've got an '82 Matsuura MC-500 in my garage. I've got it wired up with an RS232 cable (actual serial port on my PC). I will often find that it is missing end of blocks, or even dropping a J0. I read that running it too close to wiring, or fluorescent lights can cause this, so I rerouted the wire as best as I could. Still does it. Also, on long files, it will just drop the last half of it, it seems. Baud rate was originally set to 1200. It did it then. So, I jumped it up to 2400, still did it.......

I gave a preliminary answer to your question in that other Forum, but at least you have stated the control and model this time around.

Please, post:
1. the cable configuration being used
2. the Handshake method being used
3. the data transfer software being used

Regards,

Bill

[gearsoup]

The cable config...I called up my local machine dealer and asked for an RS-232 cable, about 36 ft long. I've bought cables through them before without issues.
Yes, it's shielded.
Baud: 2400
Parity: Even
Data Bits: 7
Stop Bits: 1
Handshake: Both

Software is NCNet-Lite. Why, because it was free, and I've used it before without issues, granted on much newer equipment

[John Bennett]

NCNET-LITE (cadem.com) is a great program, but if I use their connection literature, you have not configured the same (stop bit and handshaking). You might also want to check the cable pinout per diagram to double check.

[mike_Kilroy]

Originally Posted by gearsoup The cable config...I called up my local machine dealer and asked for an RS-232 cable, about 36 ft long. I've bought cables through them before without issues. Yes, it's shielded.

Have you tried a shielded cable only 2 foot or so long? does it have same problem or not? very good diagnositic tool to do this;

if no prob then u have noise picked up on the 36ft cable.

either change shielding around to find better way or shorten it or bite the bullet and buy a couple rs232-422 converters and put on on both ends and send rs 422 across the 36ft (as it should be) instead.

rule of thumb is often dont go over about 6-10' max on rs232 in noisy environment (any with servo/spindle motors/drives).

sometimes you can squeek by with changing shielding..... someone asked if shield tied to pin 1 - i did not see answer. worth try if not. is shield soldered to the metal db9 shell on one end? both ends? try cutting pvc off outside jacket of cable at one then other end and use tie wrap to tie wrap the exposed shield directly to the chassis of the computer case and other end metal case/ground. is the computer chassis tied to good ground with a wire? the other end tied to machine and or ground? see? there are a LOT of things you can try - ONE AT A TIME - to try to find a happy point.

[angelw]

Originally Posted by gearsoup The cable config...I called up my local machine dealer and asked for an RS-232 cable, about 36 ft long. I've bought cables through them before without issues. Yes, it's shielded. Baud: 2400 Parity: Even Data Bits: 7 Stop Bits: 1 Handshake: Both Software is NCNet-Lite. Why, because it was free, and I've used it before without issues, granted on much newer equipment

gearsoup,
Your cable length of 36 feet will give you no issues. RS232 standard is explicit with regards to cable length, with the Standard originally being based on 50 feet, and later on, a capacitance of 2500pF to allow maximum communication speed of 19200 to occur. Therefore, cable having a capacitance of 50pF/ft would give a maximum length of 50 feet. If speed is reduced by a factor 2 or 4, the maximum length increases dramatically, as shown in figures obtained by test done by Texas Instruments years ago.

Using a cable with low capacitance allows you to span longer distances without going beyond the limitations of the standard. For example, a cable with a capacitance of 17 pF/ft will allow a maximum cable length of 147 feet (2500pF/17) at maximum speed.

Baud Rate ---- Cable Length
19200 ---------- 50
9600 ------------ 500
4800 ------------ 1000
2400 ------------ 3000


Make sure the cable you're using is low capacitance, no greater than 50pF/ft and that it is Shielded.

The cable configuration for Xon Xoff Handshaking is as follows:

Machine Side -------------------------------------- PC Side
DB25 Male Connecter ---------------- DB25 Female ------- DB9 Female
1 ----- Cable Shield ------------------ Not Connected ----- Not Connected
2 -------------------------------------------- 3 -------------------- 2
3 -------------------------------------------- 2 -------------------- 3
4
| Bridged
5

6
|
8 All bridged
|
20

7 ------------------------------------------- 7 --------------------- 5

Check the following machine parameters are set thus:
6000 - Set Bit 7 to 1 (ISO format)
6003 - Set Bit 1 and 5 to 1
6021 - Set 1,4,5,6 to 0
6022 - Set Bit 0 and 1 to 1
6026 - Baud Rate 00011000 (2400 baud) Starting point
6028 - Baud Rate 00011000 (2400 baud) Starting point

Set the PC software as follows:
Handshake method = Xon Xoff (Software)
Baud Rate = 2400 (Starting point)
Parity Bit = Even
Data Bits = 7
Stop Bits = 2

I note that you have been using 1 Stop Bit. This will not stop communication from occurring, but it is more usual to use 2 Stop Bits when communicating with machine tools, where a noisy (electrical noise) environment is often the case. The stop bit identifying the end of a data frame can have different lengths. Actually, it is not a real bit but a minimum period of time the line must be idle (mark state) at the end of each word. On PC's this period can have three lengths: the time equal to 1, 1.5 or 2 bits. 1.5 bits is only used with data words of 5 bits length and 2 only for longer words. A stop bit length of 1 bit is possible for all data word sizes. Accordingly, 1 or 2 Stop Bits will work, but 2 Stop Bits is preferred.

Grounding the Shield at both ends (both devices) is not such a good idea unless you can be sure that both devices seek Ground at the same place, and can lead to Ground Loops if not. A Ground Loop can occur when any two devices are grounded in Different Places, or if one device is not grounded well enough. For example, you may experience a ground loop when you connect a PC and a CNC control together with a serial data cable, if the CNC machine has a ground stake driven through the shop floor, and your Personal Computer is grounded to the AC wall socket, or if one device is not grounded well enough. The Ground Loop occurs when there is a different electrical potential between the Grounds of the two devices. This results in an electrical current being conducted through the data cable, and can burn out the IC chips that send and receive the RS232 serial signals if the difference in potential is greater than about 30 volts. Accordingly, unless good grounding to the same ground can be assured for both devices, its recommended to ground the shield at one end only; usually the machine end.

For a test, connect the PC to the control with the data cable just laying on the floor well away from any electrical cables. If you really have to cross over or under any power cables, ensure that you do so at 90 degrees.

The software you're using should be OK. If you still have problem, try using another PC, or install another Serial Port to the existing PC. Install a Serial expansion card in preference to a USB to Serial adapter. It will be cheaper and less likely to give you problems.

Regards,

Bill

[mike_Kilroy]

gearsoup, you've gotten more ideas and suggestions and comments....

It would be mighty good of you to let us all know how you are coming along; especially in light of some disagreement over the basic usability of RS232 in this type of environment.

[John Bennett]

Also under Port Settings for Com port go to advanced setting and try turning off the "FIFO buffers" might help

[angelw]

gearsoup,
The suggestions made are to eliminate causes of possible problems, and is how one would go about establishing Comms in the first instance. But the fact that you lose the complete second half of a long program is not typical of EM interference issues, cable length, or any of the other suggestions made.

1. You haven't stated if you get any alarm being raised; likely if you're getting a buffer overflow, but this issue would be highly unlikely at the baud rate you're using.
or,
2. that at the end of the transmission of a long program by the PC program, does the control behave as if its received the EOF, notwithstanding that the whole of the second half of the program has been lost, or does the control seem like its waiting for more data?

Regards,

Bill