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cp341 for comunication with one trasmitter and onme PLC 3152DP

Created by: Frank681 at: 9/20/2011 2:36 PM (7 Replies)

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9/20/2011 2:36 PM	Rate (0)
Frank681 Posts: 9 Rating: (0)	Hi , I use a cp341 for comunication with one trasmitter and onme PLC 3152DP , the trasmitter send contuos data in rs422 ( ascii format ) in the cp341 i have rx led gren and blink the tx . I think not need to use the P_SND_RK FB 8 but only the P_RCV_RK FB 7 is correct ? I have try to use the FB7 parametrize the data but not have NDR . I have check the configuration of paramater and think all OK , sure I make mistake but non say where. thank's in advantage. Best regards Claudio Splitted from CP 341.
Frank681 Posts: 9 Rating: (0)	Last edited by: O_Moderator at: 9/20/2011 3:19 PM new subject after splitting
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9/20/2011 4:19 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	You will need both P_SND_RK and P_RCV_RK FB's. Modbus is a query - response protocol. It has one (and only one) master, and at least one slave device on the network (but you may have up to 32). In very simple terms, the slave is totally passive. It will do nothing but wait for the master to ask for data (the request). If the request is valid, the slave will send the data back (the response). In master mode, the S7 will use P_SND_RK to send the request and the use P_RCV_RK to receive the response. Conversely, in slave mode, the S7 will wait for a request using P_RCV_RK to receive it, and if the request is valid, will use P_SND_RK to send back the response. Please follow the modbus example project included in this thread.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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9/21/2011 1:25 PM	Rate (0)
Frank681 Posts: 9 Rating: (0)	OK But my trasmitter , send in continuos the data not need to ask nothing , infact I have the RX led in CP on and some time blink the RX , my problem is non have found the way to receive the data. the trasmister work in rs422 38400 Baud , 7Bit ,parity even and use hex 04 end caracter of string. I have test some setting with end caracter and none , with xon/xoff and none ,but in the fb7 not have done at 1 have no error and the status is 00 , i think make some wrong but not say where. i have attached the manual of trasmitter thank in advantage best regards. Claudio Attachment 120244.pdf (203 Downloads)
Frank681 Posts: 9 Rating: (0)
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9/21/2011 4:10 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	You put your question into a thread that was discussing modbus, so I assumed that you also had a modbus protocol related problem. However, the time of flight sensor is not a modbus device. It uses a propriety protocol which the CP341 will not support as standard. You will have to parameterise the CP341 for plain ASCII point-to-point communications protocol, then write you own protocol driver code for the time of flight sensor that sends ASCII data over this interface. Just saying that it is RS485 is not the whole story. RS485 is just an electrical standard. Taking a telephone as an analogy, the RS485 bit is the telephone connection, the protocol is the language you speak over the telephone. Just having a telephone connection is not guaranteed that you can communicate with the other party, you have to speak the correct language as well. Do not use XON/XOFF. This is a very rare and old form of data flow control and it hardly ever used these days. It also embeds control characters into the data stream (DC1, DC3) which will confuse the time of flight sensor interface. I would set flow control to none. I also suggest that the "End of receive message frame" setting should be set to "On expiry of character delay time". The character delay time should be set to (I suggest) 4mS. This should quite nicely trap the received data packet (which you will need to decode - see below). Turning attention to the protocol for the time of flight sensor, it seems that it is also a query response protocol. It appears that the time of flight sensor will not send any data or perform any actions unless it is sent a request. The S7 would need to send a request thus:- STX (02Hex), COMMAND, DATA, EOT (04 Hex), where COMMAND is a 3 digit ASCII string for the desired command (e.g. 'GAP', 'ECM' etc.) and DATA is additonal ASCII data that the command may need (not all command have additional data so it might not always be needed). The Time Of Flight Sensor would then replay with either:- a) NAK (15 hex) - Negative acknowledgement, meaning that the command or data is invalid or not recognised b) ACK (06 Hex) - Positive acknowledgement, meaning that the command was accepted but no data was returned, as the command was not one that asked for any data. c) Data - ASCII data response for which the command asked for.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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9/21/2011 4:37 PM	Rate (0)
Frank681 Posts: 9 Rating: (0)	Hi , I have posted the tread in other place , but is splitted here from moderator . In the L7 trasmitter is set repeat ( this option send the measurment in continuos not need ask ) ,y problem is have no data when use FB7 P_RCV_RK , tnak for the setting now try to use the recomended setting for comunication. REPEAT or SINGLE: REPEAT: the sensor continuously sends measured data via the serial interface without waiting for a request. this is default setting for trasmitter. best regards Claudio
Frank681 Posts: 9 Rating: (0)
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9/22/2011 12:04 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	Ah yes, you are correct. I did not spot the REPEAT / SINGLE modes. So just parametertise the CP341 as I suggested and call the P_RCV_RK FB cyclically. Be aware though that it may take several cycles for all the data to be received, especially if the data packet is large. The NDR output is only valid for one cycle. It is not clear from reading the documentation if NDR is set when all data is recieved or just new data is received. So when I have used this function in the past, I have played it safe and kept a count of the received data size by adding LEN to and accumulative value (e.g. TotRXBytes) every time NDR is set. This will then keep and count of the total amount of data recieved from the CP341. Something like this:- 10: CALL P_RCV_RK IF NDR = TRUE THEN TotRXBytes = TotRXBytes + LEN; END_IF; IF TotRXBytes < ExpectedPacketSize THEN GOTO 10 ELSE TotRXBytes = 0; Process data packet END_IF; When I have received the amount of data that constitutes a full packet, I can process this data and zero the accumulative count (TotRXBytes) ready for the next packet. You will have to know how much data you are expecting for each data packet. It would seem that the whole data packet is referred to as "GAP". This is made up of a lot of smaller items (ECM, GDB etc.). So I expect that you can simply add up the sizes of all the smaller items referred to in the "GAP" to get the expected packet size.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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9/22/2011 2:50 PM	Rate (0)
Frank681 Posts: 9 Rating: (0)	Hi OK but in the P_RCV_RK the LEN is an OUT data , i think in this pin have the len of data received I need one clarification , the P_RCV_RK have one istance DB ( exmaple db7) create in automatic and one DB set in DB_NO and start address DBB_NO , i not say How does it structure the db, think to is necessary a STRING where to put the data received or a WORD , be able to help to understand me this? best regards Claudio
Frank681 Posts: 9 Rating: (0)
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9/22/2011 4:35 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	Yes I am well aware that the LEN is an output. Hence why I am only reading it's value (I never write to it). You will need an instance data block for the P_RCV_RK call. You will also need another shared DB for storing the received data into. The DB_NO is set to the number of the shared DB you are using to store the received data in (not the instance DB). The DBB_NO is the address with the shared DB that the data will be stored at (0=Byte 0, 8 =Byte 1 etc.). I suggest that you just use a value of 0 for DBB_NO. The structure of the shared DB can be anything you want it to be, INTS, WORDS, REALS, BYTES etc. It can be all the same data type or a mixture of data types. To make it easier to understand the data from the time of flght sensor, it would be best to make a structure that is the same as the data it will be sending you.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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