1100 baud rate dynamic change

I have a job using 1100. I need to change the baud rate with programming. Customer want to change on the fly without a computer. I don't see an easy way to do it does anybody else?

That's an unusual baud rate. May we know the device?

Sorry Bernie I am using a MicroLogix 1100. The baud is usually 9600 or 19.2

The user's manual says that the baud rate, which is held in the high byte of S:15, is read only. I don't know any magic tricks. Are you somehow changing connections while running between two different devices which have different baud rates?

I thought it was read only. I couldn't find any work around for it. I also wanted to view the checksum on the LCD screen but it is not accessible

You can programmatically change the serial port configuration of a ControlLogix-family controller, but not an SLC or PLC family controller (including the MicroLogix).

The workaround I remember trying in the SLC family was using a tiny relay to momentarily connect Tx to Rx, then sending a "Mode Change Character", but that was just for changing the mode from System to User and back. I cannot think of a way to change the serial port baud rate.

I've used a serial baud rate buffer/converter from B&B Electronics before.

What exactly is the customer doing that they will need to change the baud rate of a serial device during operation ?

Ken is that in the df1 manual? You have my gears turning. I am only using this MLX for an ASCII to PCCC bridge. The customer has about 100 of these things out on the shop floor with either baud rate.

OK as I type this I have a few questions the mode change indicates to me That the PLC was in system mode and not user mode. Is that correct?

the link below will take you to the idea that Ken Roach came up with awhile back ... I tested it out for him and it worked - but ONLY to change from the User Mode to the System Mode ... personally I don't know of any way to change the baud rate by using the program logic ...

http://forums.mrplc.com/index.php?showtopic=3690&view=findpost&p=13886

Jeff, you still haven't answered Ken's question: "Why does the customer need to change the baud rate?" ... maybe someone could come up with a suitable workaround if we knew more ...

Sorry Ken I missed the edit in your post.

These MicroLogix are going to be data bridges dropped into exist systems. They want my micrologix to be flexible so it can be in any of their systems. Some are only 9600 and others are 19.2. Their preferenc would be to set the IP address and baud via the lcd.

DISCLAIMERS: these are just ideas off the top of my head – something to think about that might be a wild goose chase ... this is based on an SLC-5/04 – but it SHOULD work on your system too ...

first consider Ken's idea that I linked to earlier ... specifically, we KNOW that if we tie the processor's "transmit" pin back to its own "receive" pin – we can force the processor to "TALK TO ITSELF" using an AWT instruction in the ladder logic program ... more specifically, we can have the processor SEND a prerecorded string FROM its own memory – back TO its own memory - through the serial port ... the only extra hardware necessary to do this is a DB9 connector from Radio Shack which has pin 2 tied to pin 3 ...

now consider that there is some (unknown) string of ASCII characters that RSLogix500 sends to the processor in order to set the baud rate to 9600 – and also another similar string of ASCII characters which sets the baud rate to 19,200 ...

we MIGHT be able to find the syntax of those "CHANGE THE BAUD RATE" command strings listed in the DF1 manual ... but even if we can't find the syntax documented, we SHOULD (hopefully, prayerfully) be able to discover that syntax using the following method ...

I'd connect a computer running RSLogix500 to the serial port of the PLC – using the standard "go online" procedures ... BUT ... I'd modify the connecting null-modem cable (just two wires) so that I could also make a "wire tap" connection for the serial port of ANOTHER computer to the same "network" ... this extra computer would be running an "ASCII monitoring" program – and would "listen in" on the DF1 "programming" type commands being sent from RSLogix500 to the PLC processor ... MONITOR.EXE (vintage 1994) is a simple little program that I've used for stuff like this before ... I'm sure that there are others out there too ...

once connected, I'd repeatedly use RSLogix500 to change the baud rate of the serial port – back and forth between 9600 and 19,200 – while recording the command strings on the "extra" computer ... given a helpful tailwind and a hearty breakfast of Wheaties, we SHOULD be able to discover what mysterious DF1 commands RSLogix500 uses to change the baud rates ...

then I'd try to program those DF1 commands into STRING type memory locations – one STRING for the 9600 command – another STRING for the 19,200 command ...

now I'd try to send each one of those commands FROM the serial port – back TO the serial port – using the "foldback" pinout arrangement that we started out with ...

now then ...

IF (big IF) all of that could be made to work successfully, I'd try to use two spare inputs (probably from the keypad, etc.) to have the PLC initiate either one of two AWT instructions ... one instruction would send the 9600 baud rate command – the other instruction would send the 19,200 baud rate command ...

so ... in theory ... (based on what I think you're trying to accomplish) ...

suppose that Brutus needs to swap out a processor from spare stock ... the program has already previously been loaded – but the proper baud rate still needs to be selected ...

Brutus plugs in the handy-dandy "foldback" connector – then presses the correct key sequence to send the proper baud rate command ...

MAYBE – just MAYBE – we could get this idea to work ...

that's the best I've got so far ... sounds like a fun project to play with ... I'd be willing to bet (more than pocket change – but less than the rent) that something along these lines could be made to work ...

but ...

another simpler (and therefore probably "better") way might be to just keep TWO processors on the customer's "spare stock" shelf ... one loaded and clearly marked for 9600 – and the other loaded and clearly marked for 19,200 ... a nagging little voice keeps telling me that there's going to be SOMETHING else different (beyond the baud rate) between these two individual programs ...

Ron I downloaded the DF1 manual last night. I fell asleep while reading it. I was looking in chapter 7 under the communication commands for a set baud rate. Knowing that Ken didn't offer this I wasn't holding my breath that it was documented.
So now we get to have the fun of undocumented operations. I have a serial snooping program called Docklight. (One that Ken has recommended before). I plan on changing the baud several times. The exact same way to recommended. The entire time capturing that serial data and saving it. Then cheat a little and use a program called "Compare it" use that to compare the different text files. HOPEFULLY I can find that string just like you have outlined.
One of the many concerns is that the String data will be to large to keep in this small processor's memory. You are 100% correct I think this will be a FUN thing to try.

The way I see it is what is the worst thing that happens I learn some of the DF1 protocol? I will be learning something. My dad and more than a handful of old timers say you can learn something every day. My little spin on it is " If you are not learning something new everyday. You are not paying close enough attention"

As I type this I am thinking I wonder how to get the checksum out if the processor. I think that Just made my list of thing to monitor also. I ASSuME that the checksum is stored in the processor because if we think back to the fixed SLC PLC days. How many threads have we seen about program checksum does not match online image? I will edit this post shortly with and example.

I'm not connected to a PLC here but as far as I remember the only way to change the PLC baud rate is by changing it in the offline program and re-downloading. If so there may be NO 'change baud rate' command, only the makeup of a certain part of the download which may not be able to be extracted from the rest.

I am 90% sure you can change the baud rate while online. Ofcourse it will kick me offline if I'm online serially. I plan on atleast trying it this week. I have to find a processor mine is at the customers.
I have a few micrologix around but no 1100. I ASSuME the processors will respond the same to the commands. I will see probably mid week.

Guys Thanks for your help. I will get back to this one. It will probably be buried a few pages in the archives before I get to this. So you guys may see some PM when I update this.

Jeff

It sounds like your customer is not comfortable with RsLogix to me. Is this a correct assumption?

What about using the micrologix program storage device? you could have 2 units each with its own program and engrave the baud rate on the units or something like that?

These are real simple units and there is really nothing for them to get wrong and to me it's the cheapest and most simple solution.

Here is a link to the unit i am talking about http://www.ab.com/en/epub/catalogs/12762/2181376/2416247/1239756/2165757/

List price is 671.00 here is a link http://raise.rockwellautomation.com...ents.asp?CID=16164AE4B2D140008DD7F025A8F7901C

Radwell may have it cheaper.

Here is a picture of the unit. It may be beneficial to take it apart and fix the switch to the "To PLC" position to make it pretty much error proof.