Hello,

sry but I don't understand this, look at your MOVE instruction, it looks like DW value, then you have defined your DB10 offset 50 as INT, but you move value 16#2 to that DB as DBB, but this is probably DB10.DBW50. So I think lot of missunderstanding, but I know, you're testing, ok. But pls for first look carefuly to type interpretation. Just one question, that INT number in DB11 after that SEND buffer is only storage address or also you can SEND that INT to CP340? If yes, that can be maybe also problem, because that INT can have value 16#0200 not 16#0002, so value is DEC 512  Give info pls.

Update: what I want only say is, that better if you want SEND to CP some other data as BYTE, carefuly interpret this as BYTE sequence, also right back conversion on other side.

Duris, 

you were right i used a dbb instead of a dbw. and now it's working. i sent data from my cp340 back to the same cp340. 

i only managed to do this when i selected in the hw configuration ascii. but when i select 3964r it doesnt work.   anyone an explanation for this. the "fb3,  P_SEND" block has also a status output if i monitor this 

i get the code W#16#070B.  i googled for the error list but couldn't find it 

gr gerard

Hello,

in your situation ASCII protocol is right option, because that 3964R protocol you can prepare f.ex. serial connection to Simatic S5 station. If you still want investigate on that 3964R protocol, maybe this topic show relevant links, or simply Wiki can help also:

Communication Protocol Siemens 3964R

As I said in my previous posts, for first is important select right options in CP HW settings, mean right protocol, speed and other communication settings depended to your communication partner.

Update: due Status value, pls look at Help on Siemens SW for needed instruction - SEND, RECV. That 16#070B depends to that 3964R protocol, so it's not important to you.

Hello Navnag and other, 

A few posts ago you advised me to use a usb to rs485/rs422 converter, to test if the module works. 

so i arranged such a device and installed the drivers.  but now i need software, searched for dockwise but i don't know exactly which one i need. can you give me a link or something 

gr gerard

Hello,

you can use simple Hyper Terminal, it can be used with selected COM port on PC and send/receive frames. For basic testing I think is suitable. After start cancel that messages about Telephone settings and only select right option if message about Serial Port or TCP/IP appear.

Hello all,

First,  thanks to all who are helping me.

But i moved on with my project,  and now i know how i have to send data from a db and how i have to receive it into another db.  And that other thing of how a message goes with slave adress, function code, starting adres etc, is also clear to me. In the attachment i,ve put those two together. but where in that fb3 i have to fill in that slave adress11 and where in the fb3 i have to fill in the function code 03 etc.

and than also that cyclic redundancy chech.  trying to understand it i,ve searched on the internet. but every explanation that i encounter over crc is hudge complicated, on youtube movies over this subject are also hudge,  you can roughly say that the enigma that the germans used  is easier to understand than crc. that calculation how on earth do i program that

gr gerard

Hello,

pretty very interesting info from you, you're implementing Modbus protocol? You can, nothing against to that, but with this system (what you start to do) you will need prepare, as you said so much other functionality manually, also that CRC. Look at that help what you have, address and function code can be putted to your TX DB where you have array of your BYTES, as help show. Look, on more cases you prepare Modbus communication with CP341 module, you also need pay (money) for dongle to that module depended to your requested protocol. In this case you will have prepared instructions to easily implement that communication. You have CP340 not CP341? In this case no chance, you must make hard work implement that Modbus manualy, but it can be achieved. Your thoughts? Pls give info, because is important. Isn't communication as communication... Everything must be explained clearly for first.

gerard32

thanks, now i understand. Function code, slave adress i put them in my db.

for what is exactly that dongle why is it nog integrated in  cp itself. 

 Siemens Does not provide Modbus RTU library for CP340. It is only available for CP-341.
The library is chargeable and comes with a Dongle which is required to be plugged on the back of CP341 for enabling the driver.

Several users have developed  much simpler and Free solutions for CP340 as well as CP341 ( Don't need any dongle ). Pl See one such Example in the below thread by Saravana kumar:   

Modbus Sample Project

For Understanding Modbus in detail, please also read the following thread by Smiffty :

Modbus General Description

gerard32

so i arranged such a device and installed the drivers.  but now i need software, searched for dockwise but i don't know exactly which one i need. can you give me a link or something 

You can download the softwares from these links :

Docklight

Modscan

MBPoll

Hope this helps

Cheers
Navnag

Duris,

thanks, now i understand. Function code, slave adress i put them in my db.

for what is exactly that dongle why is it nog integrated in  cp itself. 

you said: "you must make hard work implement that Modbus manualy, but it can be achieved."  what do you mean with this.

You wanted more info.        The reason i want to know this is that there is an upcoming project for me in which a modbus communication is used. for that project i already have a modbus manual about the 'modbus slave'  so i'am already trying to do something in advance. But some time ago they told me that that modbus connection on the slave.  isn't a modbus connection but it's a 20-ma tty current loop connection but it works a little bit the same like modbus (they said). Is that really the case, with modbus you  can read registers . and with 20 ma tty the adresses and stuff is the same? because when they told me this, i kind of lost the track. if it's 20 ma tty, i need some more info right?

gr gerard

Hello,

why Siemens implemented Modbus protocol as posted, know Siemens  Why I said about hard work, look, I don't know what your project needs, but Modbus is big, there are so much registers for data and if you want implement it, you probably must prepare also so much types of messages with correcr CRC/LRC counts, because then your defined communication fails. Sry, but probably now I understand that you are experienced and communication isn't big problem for you. 20mA TTY CP340 module act as other serial CP30 module (if we take ASCII protocol), but on other signal system. On 232/485 modules system working on Voltage change, here on TTY on current change, so this is difference. As you see, probably big advantage in signals interference area. If you want investigate next, pls look at CP340 manual/communication, there is also schema and cable/connector wiring to partner. But what I must say (my opinion), in this time RS485/422 modules are more used, never used that TTY only on my S5 stations, so I think is old system of connection, maybe widely used at 70/80-es era. My question is if you'll have device with that TTY interface, Modbus has nothing to that, it's only about implementation. If you can, check infos about interface on that device. Hope give you other helpful infos to understand. Look at Navnag's post, there are also usable links to good programs which can be helpful to you, better then HyperTerminal. Give info pls.