Post by mondinmr on Direct Pointers in IOMapping for EtherCAT with IoDrvEthercatLib.ETCSlave_Dia ^{CODESYS Forge talk (Post)}
Using SDO, I can read the EtherCAT mappings and offsets from various registers like 0x1c12, 0x1c13, etc. When I obtain registers mapped in the PDOs and various offsets, I could technically access directly to the statusword, controlword, etc., if they are mapped. I have noticed that on IoDrvEthercatLib.ETCSlave_Diag I can find pointers to the input and output buffers. However, although the input buffer can be easily read by referring to what has been obtained from the SDOs, it is not possible to write to the output buffer, as it is overwritten in each cycle by the data from the IOMapping task. Is there a way, knowing an instance of IoDrvEthercatLib.ETCSlave_Diag, to obtain the pointer to the first data in the IOMapping? The offsets are identical to those of the PDOs, but obviously the data is a copy. For me, the cleanest thing would be to access the pointers on IOMapping, for DS402a devices to retrieve the key data and point them to internal references. I need to know this as, having developed our own motion library, I would like to simplify the initial setup by eliminating unnecessary and nonsensical mappings that can lead users to unnecessary errors. In the current version that we have been using for years, we have to map everything manually. I would like to pass only the slave reference to the FB_init constructors and eliminate the mapping.
Last updated: 2024-02-12

Post by paulorb on STRUCT AT %MW1000 ^{CODESYS Forge talk (Post)}
Hi I am trying to use STRUCT to parse commands from Modbus/TCP, Modbus client will fill the bytes related to a specific command (type, parameters), then PLC (Codesys) will access the command parameters. A STRUCT will simplify a lot the process of parsing the data, so I don't need to parse byte per byte, address will be mapped to a struct and I can use it for parsing the data. From what I understood, the compiler does not allow me to specify the location of the struct for a %MW register. VAR_COMMAND AT %MW1002: structGenericModbusCommand; This will throw: Bad declaration, use '%ML' for 'structGenericModbusCommand' variable But If I change it to %ML, when you go online you see that it is actually allocating the struct in another memory address. When we go online, on GVL we can see: VAR_COMMAND. structGenericModbusCommand %ML1002 commandType COMMANDTYPE %MB8016 ... %MB8020 I am not specifying a pointer or a reference it is a struct type, why is it mapping to a %MW location (random one). How can I control where it is mapping to? I need a consistent way to map STRUCT to specific modbus address. Is it possible? Thanks, Paulo Note I am using a Codesys OEM: Schneider Machine Expert Logic Builder (M241)
Last updated: 2024-08-13

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