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;
