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RS232 - Simple USB compatibility (Takisawa TC-20)

RVGM

Plastic
Joined
Jul 2, 2019
RS232 to USB has been discussed a lot over the years and I'd like to know if anyone has any up-to-date recommendations for the simplest way to use a USB stick (or PC) to load programs onto a machine with only RS232.

Our situation:

One of our older machines is a Takisawa TC-20 with Fanuc Series 21-T and we need to connect a computer or USB drive to send NC files to the machine. The only connection the machine has is a RS232 DB25.


We don't have any computers with built-in RS232 ports anymore, so an adapter of some sort is looking likely. PC is an option, but if we could get an adapter/reader for a USB stick without needing a dedicated computer, that would be much better.


Any recommendations for specific adapters or brands would be great.
 
those cables are usually build null-modem rather than full handshake, IIRC.

Any USB to serial adapter should work, but you'll probably end up with a DB9 connector on said adapter. DB9 to DB25 null modem cable should work.

There's plenty of software you can use to send code over serial, you just need to know which COM port your USB adapter is on.
 
I just got a cheap desktop and put a serial card in it. You can get serial (DB-9) or parallel (DB-25) PCI cards for $15-$45 at Newegg.

Bonus is I can use the computer to pull up prints, edit programs, etc. right next to the machine.
 
A lot of old RS-232 connections don't work well because RS-232 is a 12vdc specification, while USB is a 5 volt specification. So unless the adapter correctly implements the full 12 vdc specification voltage levels the communications can be flakey. Alleb Bradley PLCs with serial ports don't work at all without a special adapter. That wouldn't be a big deal other than they were about $300 each and so prone to failures we always carried two if we were working on a job out of town!
 
A lot of old RS-232 connections don't work well because RS-232 is a 12vdc specification, while USB is a 5 volt specification.

It isn't a Voltage-level nor even protocol spec anyway. It is only a connector spec that provided agreed pin assignments for a common set of telephone and telegraph functional signals, not all of them necessarily utilized on the same connector at the same time or even "at all".

N'er mind. No need to re-invent it.

"KISS"

Just use what others with the same gear report as working well.
 
Tripp Lite Keyspan High-Speed USB to Serial Adapter, PC & Mac (USA-19HS)


We use this in my shop. Works well with DNC4U but it's not capable of drip feeding through the USB. You will have to download and install the driver that's available at the trip-lite web site if I remember correctly. A google search will find it as well. You will still need a null modem cable to go from DB9 to the DB25 connector. Hope this helps.

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Tripp Lite Keyspan High-Speed USB to Serial Adapter, PC & Mac (USA-19HS)


We use this in my shop. Works well with DNC4U but it's not capable of drip feeding through the USB.......

Do you know why the Keyspan USB to RS232 adapter will not drip feed using DNC4U? DNC4U recommends Keyspan if one must use a USB to RS232 adapter. I have used a Moxa USB to RS232 adapter with DNC4U and it would drip feed perfectly.
 
Don't quote me on this but they didn't used to recommend it as I remember reading it on their website. This was years ago so maybe it's different now. I remember reading that they had problems with the reliability of the USB side of things being able to "drip" the data. I personally have never tried it, I just remember reading about it. Maybe you can do it now. That's awesome if you can. Means I don't have to buy anything new to do it if I need too. [emoji16][emoji16][emoji16]

Sent from my Moto G (5) Plus using Tapatalk
 
Completely true that some USB to RS232 adapters are not reliable enough to drip feed. Before Tripp Lite bought out the Keyspan line, their adapters would drop data. Belkin did too. Both of those were OK if you just were loading programs to memory. Drip feeding, they would drop data. Sometimes the control would alarm if the data was messed up. Sometimes it just skipped a move.
 
From the small bit of research I have done it appears that the best adapters use a chip from FTDI.

FT2232H

When I first started setting up machines to drip feed programs, I started using a test program that made thousands of .01" incremental moves in all 3 axes with an equal number of negative moves and positive moves. I would start the program at machine zero or with the display zeroed and at the end of the program, the display should be back to machine zero or the display should show zero. If a move or moves got dropped then the position would be different by some multiple of .01".

A pre Keyspan model from Tripp Lite and a Belkin adapter would usually fail on this test. Typically at the end of the run, 1 or 2 axes would show .01-.03" error.

I have tested the MOXA and DNC4U combination with a file as large as ~4mB several times with no failures. I have also tested my current setup which uses a PCMCIA Expresscard to RS232 adapter with DNC4U with the same ~4mB file with no failures.

I use hardware handshaking on my cable configuration. I have always felt that a hardware handshake must be more reliable than a software handshake. No empirical proof of that, just an opinion.
 
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I can report that the Shoplink USB deal drip feeds just fine. The only control I tried it on was a Dynapath Delta 20, which spools data from the RS232 into memory until full, then draws more in as it's processed. I created a file twice the size of available memory, put in on a USB stick, then watched it run, No hiccups.
 
A lot of good suggestions here, thank you.

Reliability is my main concern (although cost is always a factor too) and many of the products I’ve come across online seem to struggle with drip feed.

The DNC/Titan looks like an interesting solution, mainly due to it’s all-in-one simplicity, but I’ll take a look at all the suggestions in the thread.
 
I have had success with FTDI based USB>Serial adapters from amazon ($12ish), or a $20 PCI-E to serial card. I have a computer in my shop sending and receiving data from machines including huge dripfeed programs with no problems and probe inspection data. Homemade null-modem cables, software handshake, and using parity for error detection. Fanuc, HAAS, and Milltronics controls all using the same arrangement.
 
This is what we use as an alternative to our DNC system.
We have an older model/setup, but it is very easy to use.
A bit pricey ($2500.00'ish), but no additional software or accessories to deal with/setup. (Aside from your USB/SD card.)
Software is configurable, and allows you to build a settings database (RS-232 config) for easy recall of each different control.

9-pin, 25-pin compatible
USB/SD Card/Bluetooth
Send/Receive/Store/Edit programs

CncGcoderHD-T
 








 
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