Process Data is exchanged cyclically with the EtherCAT MainDevice. Process Data Objects (PDO) are objects from the object dictionary mapped as process data. Therefore, the object dictionary must be configured before configuring the process data objects.

PDO configuration example

A PDO is an object filled with PDO entries. These entries are objects from the object dictionary which can be mapped as PDO. Therefore, there are few things to consider.

Index 0x1600 to 0x17FF are reserved for RxPDOs.
Index 0x1A00 to 0x1BFF are reserved for TxPDOs.
Object entries must have OBJACCESS_RXPDOMAPPING or OBJACCESS_TXPDOMAPPING flags.

Therefore, it's not possible to map an object only with OBJACCESS_RXPDOMAPPING flag in a PDO with Index 0x1A00 to 0x1BFF and vice versa.

Examples

Create a RxPDO and map an entry from array object entry from CoE Examples to the PDO.

EC_API_SLV_SHandle_t*       ptSlave     = pApplicationInstance_p->ptEcSlvApi;
EC_API_SLV_SCoE_ObjEntry_t* ptObjEntry  = NULL;
EC_API_SLV_SPdo_t*          ptRxPdo1600 = NULL;
EC_API_EError_t             error       = EC_API_eERR_INVALID;
 
error = (EC_API_EError_t)EC_API_SLV_PDO_create(ptSlave, "RxPDO", 0x1600, &ptRxPdo1600);
 
error = (EC_API_EError_t)EC_API_SLV_CoE_getObjectEntry(ptSlave, 0x2100, 1, &ptObjEntry);
 
error = (EC_API_EError_t)EC_API_SLV_PDO_createEntry(ptSlave, ptRxPdo1600, "SubIndex 001", ptObjEntry);

Help functions

The EtherCAT SDK provides with a set of functions to access the process data. These help functions are available with the _PDO_ suffix. For further information please refer to the documentation.

Function	Description
EC_API_SLV_PDO_get	Get object from PDO list
EC_API_SLV_PDO_getOffset	Get PDO offset in process data
EC_API_SLV_PDO_getLength	Get PDO length
EC_API_SLV_getInputProcDataLength	Get input process data length
EC_API_SLV_getOutputProcDataLength	Get output process data length
EC_API_SLV_PDO_getEntryCount	Get PDO entry count
EC_API_SLV_PDO_getEntryDataLength	Get entry data length
EC_API_SLV_setInputData	Write input process data
EC_API_SLV_getOutputData	Read output process data
EC_API_SLV_PDO_setData	Set PDO data
EC_API_SLV_PDO_getData	Get PDO data
EC_API_SLV_PDO_setEntryData	Set PDO entry data
EC_API_SLV_PDO_getEntryData	Get PDO entry data
EC_API_SLV_PDO_setFixed	Define if PDO entries adjustable or not
EC_API_SLV_PDO_enable	Enable PDO from process data mapping
EC_API_SLV_PDO_disable	Disable PDO from process data mapping
EC_API_SLV_PDO_enabled	Check PDO status
EC_API_SLV_PDO_setAssignment	Define if SyncManager content is adjustable or not
EC_API_SLV_PDO_addPadding	Add padding to process data to avoid alignment issues
EC_API_SLV_PDO_registerAssignmentChanges	Process data reconfiguration after change on SyncManager assignments
EC_API_SLV_PDO_registerMappingChanges	Process data reconfiguration after changes on PDO mapping
EC_API_SLV_PDO_getMappingInfo	Get PDO mapping information
EC_API_SLV_PDO_getAssignmentInfo	Get SyncManager assignment information
EC_API_SLV_PDO_setMaxSubIndex	Set maximum subIndex for unfixed PDOs
EC_API_SLV_PDO_setSyncManMaxSubIndex	Set SyncManager maximum subIndex if assignment is allowed

Process Data Size

By default the process data size is limited to 1024 bytes. Below are the steps to be followed to increase the process data size to 2048 bytes as an example.

Update the maximum process data size in the project.h file.

#define EC_MAX_PD_LEN 2048

Update the user memory address of the ESC in ecat_def.h.

#define MAX_PD_WRITE_ADDRESS        0x4FFF
#define MAX_PD_READ_ADDRESS         0x4FFF
 
// Process Data Size
#define MAX_PD_INPUT_SIZE           0x800
#define MAX_PD_OUTPUT_SIZE          0x800
 
#define MAX_MBX_WRITE_ADDRESS       0x4FFF
#define MAX_MBX_READ_ADDRESS        0x4FFF

Update the ESI file.

<Sm StartAddress="#x1800" ControlByte="#x64" Enable="1">Outputs</Sm>

<Sm StartAddress="#x3000" ControlByte="#x20" Enable="1">Inputs</Sm>

Add the required TxPDOs/RxPDOs in ecSlvSimple.c and ecSlvSimple.h files.
Increase the heap memory size in syscfg if necessary.