Posted 8 Feb 2021 (edited) Hi all, New to the forum. I've been pretty much able to do the things I wanted with Beckhoff, but now I'm finally running into a problem I can't seem to solve alone. I'm trying to set-up Modbus RTU RS485 communication in Twincat3, using an EL6021. I've implemented a sample program from the Beckhoff website, but can't get it to work. I've got the feeling I need to properly set up the EL6021 but most information on the Beckhoff website is about the KL-series IO. Does anybody have experience with this? The strange thing is that, when I enable the function to read some slave's registers, BUSY is set and remains set. No timeout is triggered. I don't have a slave connected yet but I would at least expect to see something on the output of the terminal, and then a timeout. I've bridged TxD+ and RxD+, and TxD- and RxD- and set 8000:06 of the EL6021 TRUE, half duplex mode enabled). A scope connected to TxD+ and TxD- shows nothing. Code added below. I've added a GVL called 'Variable_Configuration' with the following: VAR_CONFIG Main.MB.InData AT %IB0 : MB_KL6inData5B; Main.MB.OutData AT %QB0 : MB_KL6outData5B; END_VAR And then the MAIN: PROGRAM MAIN VAR bIoSyncMaster AT %I* : BOOL; MB : ModbusRTUmaster_KL6x5B; MBLedDriver : ARRAY[1..10] OF WORD; tmpExecute : BOOL; bError : BOOL; bBusy : BOOL; iErrorId: MODBUS_ERRORS; iNoDatByteRead: UINT; count: INT; freebyte: INT; TxError: INT; TxBlocked: BOOL; END_VAR MB( UnitID:= 41, Quantity:= 4, MBAddr:= 16#0020, cbLength:= SIZEOF(MBLedDriver), pMemoryAddr:= ADR(MBLedDriver), Execute:= tmpExecute, Timeout:= T#5S , BUSY=> bBusy, Error=> bError, ErrorId=> iErrorId, cbRead=> iNoDatByteRead); MB.ReadRegs(); count := MB.MBMaster.com.Buffer.Tx.count; freebyte := MB.MBMaster.com.Buffer.Tx.FreeByte; TxError := MB.MBMaster.com.Buffer.Tx.Error; TxBlocked := MB.MBMaster.com.Buffer.Tx.Blocked; tmpExecute:=FALSE; Edited 8 Feb 2021 by HanaH typo on terminal name 1 person likes this Share this post Link to post Share on other sites
Posted 2 Nov 2021 Hello, i have a problem like this. Have you fixed it? Share this post Link to post Share on other sites
Posted 2 Nov 2021 Yes. The hardware I got from Ebay was broken. With new hardware it worked. What is your problem? Share this post Link to post Share on other sites