Skip to Content

SiePortal

The integrated platform for your product selection, buying and support workflow - bringing together Industry Mall and Online Support.

SiePortalDeutsch

Search

Home
Support Support
{{(apiData.Support | filter:{'rank':1}:true)[0].title}} Support
- Menu temporary not available
- Menu temporary not available
- Menue temporary not available
- {{item.title}}

Products & Services
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Support Support
{{(apiData.Support | filter:{'rank':1}:true)[0].title}} Support
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
MySiePortal MySiePortal
{{(apiData.MySiePortal | filter:{'rank':1}:true)[0].title}} MySiePortal
- Menu temporary not available
- Menue temporary not available
- {{item.title}}
Cart ({{apiData.CartCount}})

Navigation

CM1241 (RS485) vs. Hyper Terminal: Tx works, Rx doesn't

Created by: Marstrand at: 5/18/2011 9:44 PM (8 Replies)

Rating (2)

Thanks 5

9 Entries

5/18/2011 9:44 PM	Rate (0)
Marstrand Posts: 3 Rating: (0)	Hey guys! First of all: I am a total S7 newbie, so please bear with me. I recently bought these: https://support.automation.siemens.com/WW/llisapi.dll?func=cslib.csinfo&objId=34144059&nodeid0=44356925&idx0=Z&nav0=tree&load=content&lang=en&siteid=cseus&aktprim=0&objaction=csview&extranet=standard&viewreg=WW https://support.automation.siemens.com/WW/llisapi.dll?func=cslib.csinfo&lang=en&objid=6ES72411CH300XB0&caller=view I have been playing with TIA Portal 10.5 for a while trying to get a seemingly simple program to work - but I'm only halfway there. I want to make a simple program much like this: /tf/WW/en/Posts/40617#top .. except I don't have a screen and my CM1241 is the RS485 version. I have made a program somewhat identical to the one above, except I inserted contacts (from my input simulator board) on the "SEND_PTP"s "REQ"-input and "RCV_PTP"s "EN R"-input. Everything is (as far as I know!) pretty much standard configuration. I have not set up any special start or stop conditions. The "SEND_PTP" part works beautifully and I am able to transmit a string from the CM1241 to a PC. But when I try to write some stuff in the Hyper Terminal (or any other program for that matter) exactly NOTHING happens on the S7 system. The "Rx" LED on the CM1241 does not even blink. Clearly I am missing something completely fundamental - but what? I would guess that there is a mechanism controlling who is talking and who is listening, but if that is the case I can't seem to find it. If necessary I'll post the project here tomorrow when I'm back at my desk. Any help will be greatly appreciated. Thanks!
Marstrand Posts: 3 Rating: (0)
Suggestion To thank Quote Answer

5/18/2011 10:16 PM	Rate (0)
Kaulquappe Posts: 3093 Rating: (324)	Hello Marstrand, has your PC got a RS485 interface or do you use a converter? Regards, Kaulquappe
Kaulquappe Posts: 3093 Rating: (324)
Suggestion To thank Quote Answer

5/19/2011 7:59 AM	Rate (0)
Marstrand Posts: 3 Rating: (0)	Hi Kaulquappe, I have been trying to get it to work using this converter: http://www.moxa.com/product/UPort_1150_1150I.htm .. and this Ethernet port server: http://www.moxa.com/product/nport_5600.htm Regards, Marstrand
Marstrand Posts: 3 Rating: (0)
Suggestion To thank Quote Answer

5/19/2011 9:41 AM	Rate (1)
Aristotelis Posts: 147 Rating: (34)	Hi Well, it looks like this is a very complicated configuration you have there... I am not familiar with MOXA converters, but I can give you some hints: First and foremost, try to get your hands on a RS232 CM1241. This way you will be able to remove the RS232/RS422/RS485 converter from your configuration. If that is not possible, take into account that (most of) the USB/Serial Converters suck... This is mostly due to the USB drivers they use, but still, if you can find a PROPER RS232 com port you will be glad you did... Oh, and please - everybody who is reading this thread - DO NOT USE HYPERTERMINAL. There are a lot of good terminal programs out there... (I tend to use Bray's Terminal: https://sites.google.com/site/terminalbpp/ ) Now, you have to figure out where is your problem lying... What quickly comes to mind is this: RS485 is usually different from the RS232, in the sense that you can receive and transmit data at the same time. In RS232 you cannot do that, you have to transmit at a different time when you receive... Are you taking this into account? Marstrand Clearly I am missing something completely fundamental - but what? I would guess that there is a mechanism controlling who is talking and who is listening, but if that is the case I can't seem to find it. If necessary I'll post the project here tomorrow when I'm back at my desk. Is your PLC going into listening mode? In general, device communications work like this: 1) Device is sending data. 2) Device is going into listening mode. 3) Device is waiting for data. 4) Device receives data. 5) Goto 1. So, you have to make sure that your PLC is waiting for data on the RS485 port. When data are received an interrupt is called which handles the receive of data. If you have a signal analyser, then you can check what is coming out of the PC-USB-RS232-RS485 port. Again, try to confirm that the PLC is communicating as it should be. If you cannot figure this with your PC, then try another PLC, or a simple device with RS485. HTH
Aristotelis Posts: 147 Rating: (34)
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users Marstrand

5/19/2011 10:28 AM	Rate (0)
Kaulquappe Posts: 3093 Rating: (324)	Hello Aristotelis, it is not necessary that you put the general functions of CM1241 in question. And no user needs to make system tests with released modules. It is for sure that CM1241 is in listening mode after start up. When a send job is triggered the CM turns to send mode, sends the data und returns to listening mode immediatelly after the last send character. Even your statement regarding sending and receiving at the same time is wrong. With RS485 2-wire it is never possible to send and receive simultaneously. RS232 is a physically fullduplex interface and it depends on the use of the auxiliary signals and theused protocol whether you can send and receive simultaneously. Regards, Kaulquappe
Kaulquappe Posts: 3093 Rating: (324)	Last edited by: Kaulquappe at: 5/19/2011 11:28 AM
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users Marstrand

5/19/2011 10:48 AM	Rate (0)
Kaulquappe Posts: 3093 Rating: (324)	Marstrand Hi Kaulquappe, I have been trying to get it to work using this converter: http://www.moxa.com/product/UPort_1150_1150I.htm .. and this Ethernet port server: http://www.moxa.com/product/nport_5600.htm Regards, Marstrand Hello Marstrand, I recommend to set the stop condition to timeout (ENDCOND = 4). The converter must be in mode RS485 2-wire (PORT = 1) Regards, Kaulquappe
Kaulquappe Posts: 3093 Rating: (324)
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users Marstrand

5/19/2011 1:16 PM	Rate (1)
bakerjw Posts: 126 Rating: (18)	To clarify an earlier statement. RS485 is half duplex. It can only send OR receive at one time. RS232 typically is full duplex. It can send AND receive at the same time. Many USB to serial adapters are less than adequate. It is well advised to get a good one. Doublecheck your wiring. Ensure that the channels are connected properly. A <--> A and B <--> B. A cheap converter might still receive data with a loose wire. Does your converter have TX and RX LEDs? If so do they flash when you hold down a key in hyperterm? Try setting a low baud rate and type several keys. Sometimes it is dificult to see the LED on the CM1241 flash when receiving single characters at high baud rates. That is where I'd start.
bakerjw Posts: 126 Rating: (18)
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users Marstrand

5/19/2011 2:23 PM	Rate (0)
Marstrand Posts: 3 Rating: (0)	Hey everybody! .. and thank youvery, verymuch for all yourreplies! This is kind of embarrassing, but I think I just figured it out. bakerjw, you are absolutely right - the wiring was wrong all the time. Turns outmy different MOXA products (which are all RS485) do not share the same pin configuration! The very second i changed the wiring, the Rx LED started flashing and the "RCV-PTP" block started reacting. It looks like I still have a timing-related problem, but this should be an easy one. I still don't get how I was able to transmit information one way in the first place. I guess I can conclude that (as Aristotelis and bakerjw pointed out) my RS485 converters probably do not meet the requirements. By the way, as far as I can see the CM1241 module only supports RS485 2-wire. Aristotelis>> RS232 was never an option. This HyperTerminal (or now Bray's Terminal) programis only the first step. I planon using my S7 system to communicate with some other non-PC devices - which all use RS485. But thanks anyway. But again: Thank you all for all your suggestions! It turned out I am an *** after all .. I hope I did not waste too much of your time. Best regards, Marstrand
Marstrand Posts: 3 Rating: (0)
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users Kaulquappe

6/27/2011 11:40 AM	Rate (0)
khairul Posts: 57 Rating: (0)	Marstrand, can you share the program that you had been created.? because it can be a good tutorial for me to understand the communication protocol.
khairul Posts: 57 Rating: (0)
Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on