Siemens IPC427c and Modbus RTU (ET200sp)

[barryoc]

Hi all,


I have being trying in vein for the past 4 weeks to get a modbus master block to work on my IPC427. I have exhausted google search in attemptimg to get this to work.


Attached are the rungs from OB1 for modbus_com_load and modbus_master. I have trapped the done bit for modbus_com_load and this sets. Modbus_master will not set and the error rotates between 7001, 7002, 81E2. I have checked the comms settings in the hardware config and its correct.



At the end of the document is OB100 to set the com_rst bits for each block.


Can anyone give me some pointers on this?


Many thanks,
Barry.

 

[sigmadelta]

What hardware connection/module are you using to connect the Modbus to the IPC427?

Can you send pertinent screenshots of the hardware configuration?

 

[sigmadelta]

This is the error information, but you probably looked it up already:

16#81E2
Frame aborted: Character frame error
Check the settings for start bit, data bits, parity bit, data transmission rate, and stop bit(s).

 

[Lare]

Modbus Com load blocks set your com speed, parity and so on.
Harware config what you have setted on ptp card isn't valid after com_load is succesful.


You try to read from slave2, address 40001, 1 word, is that correct?


Also do you have RS232 or RS485 as RS485 needs biasing sometimes on Siemens card side before it works.


Also is TX led blinking on card or is it allways off?

 

[barryoc]

Hi all,


Attached is hardware config.


Lare,


TX light is blinking. Is there something in this?


Regards,
Barry.

 

[Lare]

You need adjust com speed with Modbus_Comm_Load parameters (block inputs and IDB static side parameters)



There is Modbus_com_load.BAUD , PARITY, FLOW
_CTRL and so on parametersm whic you need to code on PLC ladder / FBD side.
Also there is Static tags in IDB, which you maybe need to adjust also.
There is default on these and if they aren't same than on your slave device, coms won't work.


port parameters are changed when you req modbus com load block.



see ptp manual
https://support.industry.siemens.co...for-point-to-point-connections?dti=0&lc=en-WW


starting from page 119

 

[Lare]

look also this, port is setted 19200 with comm load block


https://support.industry.siemens.co...7-1200-s7-1500-via-modbus-rtu-?dti=0&lc=en-WW

 

[barryoc]

Thanks guys,


Have read through these and tried everything i haven't already tried and still no done bit on the Modbus_master block.



Will keep trying.


Thanks again for the pointers and help.

 

[Lare]

I can check it maybe somewhere on weekend, as I have ET200SP rack with ptp card couple meters away.

PM if needed


Still 2-4weeks study is normal for ptp if started from scratch. Still remember ET200S ptp studying hell when it was launched. It was even harder than SP series

 

[barryoc]

Lare,


That would be most appreciated.



Quick update on my situation.


No lights flashing on cm ptp module. I had slave connected and was getting RX light.



When i connect slave to pin 14 (either cable) RX light flashes.



Thanks again.

 

[Lare]

Lare,


That would be most appreciated.



Quick update on my situation.


No lights flashing on cm ptp module. I had slave connected and was getting RX light.



When i connect slave to pin 14 (either cable) RX light flashes.



Thanks again.

I sended PM messege.


There is definitly something wrong on program side. TX led should blink even if there isn't anything connected.

Maybe wrong HW ID and messages don't go to card.

 

[barryoc]

Issue resolved

Hi all,


I managed to achieve comms eventually. Followed Lare's notes on placing parametres directly on the modbus_comm_load block. Also found that my CM PtP card was not sitting in place correctly. Thirdly the A/B lines on my test slave were opposite to that of the A/B lines on the CM PtP card.


Once again thanks to all for help.


Barry.

 

[Lare]

Hi all,


I managed to achieve comms eventually. Followed Lare's notes on placing parametres directly on the modbus_comm_load block. Also found that my CM PtP card was not sitting in place correctly. Thirdly the A/B lines on my test slave were opposite to that of the A/B lines on the CM PtP card.


Once again thanks to all for help.


Barry.

OK, Coding modbus also here


It is advisible that you make MB_COMM_LOAD also after IM200SP station failure, card necessarily won't work without reinit after that (at least it was situation with step7 classic and ET200SP.)


So init if

PLC starts
RACK failure to ET200SP
If you communication failure for long time (this also repairs
rack failure, but it takes longer)