Intergrating a barcode scanner with a Micrologix 1200 B

baileyoc

Member
Join Date
Mar 2004
Posts
3
I have been trying to intergrate a Intermec 1470 barcode scanner with a Micrologix 1200. The 1200 has a single comm port with two comm protocols.
1: A default DF1 for communicating with the processor.
2: A user defined which I have set to Ascii.

I have configured Channel 0 and programmed my logic and am able to read and write to channel 0 using Hyperterminal.

I am able to read barcode info to Hyperterminal from my scanner, (using the same settings) however I am unable to read barcode data to channel 0 of the Micrologix.
I found the following on AB's Knowledgebase

"A18204 - Application Useful Knowledgebase Information Option (AUKIO):DOC. 19
Adding TTL 0-5 Vdc Input Capability to a Micrologix 1000, M1200, and M1500

Last Modified: 08/13/2002
Previously Released as #12132

General Category: s Programmable Controllers
Product(s): MicroLogix (1761); MicroLogix 1200 (1762); MicroLogix 1500 (1764); MicroLogix 1500 (1764)
Catalog #: 1762L24BWA; 1764LSP
Series / Revision:
Subject (Keyphrases): application
Summary of Technote Information:

--------------------------------------------------------------------------------
Currently as of the creation of this document no TTL DC input capability is available in the M1000, M1200, or the M1500 family of products. It is obvious that a non A-B interposing device could be used between the TTL device and a standard Micrologix dc input. However, for those wanting to connect a limited number of lower speed TTL devices to a Micrologix DIRECTLY, an application solution is possible for this functionality.

Assistance is available to discuss a specific application and to assist in the developing of this functionality for a charge of $150/hr. Complete turn-key application assistance for developing this functionality for your process can also be quoted."
-------------------------------------------------------------------
The output from the scanner I am using is TTL and I have tried a TTL to RS232 converter using every available setting with no success. ( not even a single character showing up in the buffer)

Any assistance sure appreciated.
 
The knowledge base article has nothing at all to do with what you are trying to achieve. The article is talking about 0-5 V DC inputs, not the comm port.
Also I am not sure what you mean by the scanner output is TTL yet you can read the values with hyperterminal?
 
Thanks for your reply Alan,
Your right regarding the article referring to Dc imputs not the Comm port. I should have re read it.

"Also I am not sure what you mean by the scanner output is TTL yet you can read the values with hyperterminal?"

The scanner output is TTL (0v & 5v) and on other applications where we run the imput to a Basic module we have to convert it to RS232.

We have also intergrated the same type of scanner with channel 0 of a SLC using no converter.

Using Hyperterminal I can read barcode data directly from the scanner and also thru a TTL/rs232 converter. I gather from your comment above I should not be able to read a TTL signal directly thru the comm port on my PC.
Thanks again for your imput it's appreciated as you can tell this is not my forte.
 
Figured it out with a little help.
The micrologix comm cable is a null modem , the cable attached to the scanner is null modem and when connected together they cancel each other out. All I had to do was add a third null modem cable between them as a test and it worked fine.
Go figure, Hope someone learns from my mistakes.
 
baileyoc said:
All I had to do was add a third null modem cable between them as a test and it worked fine.

Or, you could have just used ONE null modem cable... :nodi:

The signals are probably pretty dizzy after getting 'flipped' three times on their way back and forth!... :eek:

Glad to hear you got it working (AND had the courtesy to follow up with the outcome!)... :cool:

beerchug

-Eric
 
He STARTED with two null-modems, but added a THIRD to get it working. Here's (roughly) what he had...

NM1 NM2 NM3
2--. .--3 3--. .--2 2--. .--3
X X X
3--' '--2 2--' '--3 3--' '--2


You get the SAME results with just on null-modem

2-------------. .-------------3
X
3-------------' '-------------2



Any ODD number of null-modem cables give the same result. Therefore, 8743 null modems would work too, but that might exceed the maximum distance for RS-232 signals... :D

beerchug

-Eric
 
I get it, but NM1 and NM3 are built into the cables that he has. No way to get rid of both or even one of them.
 
gbradley said:
I get it, but NM1 and NM3 are built into the cables that he has. No way to get rid of both or even one of them.

Yes, that's true with the setup he has... :nodi:

The scanner has a pigtail cable, so he's stuck with that (short of hacking off the end and adding a correctly wired DB-9). The ML cable could be swapped with a straight-through version to eliminate the need for the third cable though... :confused:

beerchug

-Eric
 

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