Hey guys,

I want to establish UART communication between my S7-300 with 138-4DF01-0AB0 (ASCII card) to small robot based on arduino module. Description in attachment.

The description looks quite simple :

Sending/Receiving:

1byte flag (0xFE), 2 byte (command byte), x byte (data bytes)

Question is - which built in functions should I use to transfer data over ASCII module : S_SEND, S_RCV ?

How should I manage receiving data? Just use S_RCV and data is going to be updated automatically with proper header etc ? or first I need to send corrcet instruction type 0XF9 ?
Thanks guys for help.

hi servusik,

yes, communication works over blocks S_SEND, S_RCV.

Maybe this FAQ can help:

Function Blocks, Examples and User Manuals of the Serial Interface ET200S 1SI

What should you watch out for in particular in the parameters of the S_SEND function block for the serial interface module ET 200S 1SI during the processing of a job?

hope this helps,

regards,

Hello,

question is if that Arduino send back some message, you must test it for first without PLC, maybe with simple Hyperterminal you can send messages as are described in document. Then you can see if some messages are send also from Arduino. If Arduino doesn't send back nothing, you don't need use RCV instruction.

I think this is most important question. For S_SEND we need to create a structure and make a call on it.
About S_RCV - just a call with proper structure and controller should write data to those bytes ? I wonder because if you go to page 7 of instruction I last attached. There is that second byte (Instruction type 0xF9). For now it doesn't have sense because we can receive only 1 telegram - so it is made probably for future extension with additional telegrams to identify them. Any thoughs ?

Hello,

sry not clear to me, but this is what I mentioned in my previous post, you need give some infos about that communication functionality. Personally in my opinion very poor documentation, give us that needed info when Bot send back message, in which condition, after each your send message? How we can help you if you not provide needed infos? Also can you give clear info what you mean with that F9 command, what is not clear to you? You have access to device, we not.