309 lines
10 KiB
Plaintext
309 lines
10 KiB
Plaintext
/** \file
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\section general General
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The SOEM is a library that provides the user application with the means to send
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and receive EtherCAT frames. It is up to the application to provide means for:
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- Reading and writing process data to be sent/received by SOEM
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- Keeping local IO data synchronised with the global IOmap
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- Detecting errors reported by SOEM
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- Managing errors reported by SOEM
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The following sections show some basic examples on how to get the SOEM up
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and running, as well as making use of the process data and checking
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for errors. Since all code is local to the application or global
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variables, it is possible to tweak and optimize when possible.
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The following example shows how to add a main function that will be
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called by startup code. In this example main's only purpose is to
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spawn a new task that executes SOEM.
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\code
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int main (void)
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{
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rprintp("SOEM (Simple Open EtherCAT Master)\nSimple test\n");
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task_spawn ("simpletest", simpletest, 9, 8192, NULL);
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\endcode
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\section configuration Configuration
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Followed by start of the application we need to set up the NIC to be used as
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EtherCAT Ethernet interface. In a simple setup we call ec_init(ifname) and
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if SOEM comes with support for cable redundancy we call ec_init_redundant
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that will open a second port as backup. You can send NULL as ifname if you
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have a dedicated NIC selected in the nicdrv.c. It returns >0 if succeeded.
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\code
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/* initialise SOEM, bind socket to ifname */
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if (ec_init(ifname) > 0)
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\endcode
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SOEM is a light weight ethercat master library used in embedded systems, It
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supports only runtime configuration. It requests a BRD (Broad Cast Read) of
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address 0, all fully functional slaves in the network will respond to this
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request, and therefore we will get a working counter equal to the number of
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slaves in the network. ec_config_init also sets up the mailboxes for slaves
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that support it. When ec_config_init finishes it will have requested all slaves
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to state PRE_OP. All data read and configured are stored in a global array
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which acts as a placeholder for key values, consult ec_slave for detailed
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information.
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\code
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/* find and auto-config slaves */
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if ( ec_config_init(FALSE) > 0 )
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{
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rprintp("%d slaves found and configured.\n",ec_slavecount);
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\endcode
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SOEM has now discovered and configured the network it is connected to.
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Now we can verify that all slaves are present as expected. These
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definitions could be generated by an external tool in an offline .h file.
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The definitions could be replaced by a struct keeping slave number.
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\code
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#define EK1100_1 1
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#define EL4001_1 2
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...
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#define EL2622_3 8
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#define EL2622_4 9
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#define NUMBER_OF_SLAVES 9
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snippet
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...
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uint32 network_configuration(void)
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{
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/* Do we got expected number of slaves from config */
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if (ec_slavecount < NUMBER_OF_SLAVES)
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return 0;
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/* Verify slave by slave that it is correct*/
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if (strcmp(ec_slave[EK1100_1].name,"EK1100"))
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return 0;
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else if (strcmp(ec_slave[EL4001_1].name,"EL4001"))
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return 0;
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...
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else if (strcmp(ec_slave[EL2622_4].name,"EL2622"))
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return 0;
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return 1;
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}
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simpletest
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...
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if (network_configuration())
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...
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else
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rprintp("Mismatch of network units!\n");
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\endcode
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We now have the network up and configured. Mailboxes are up for slaves that support
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it. Next we will create an IOmap and configure the SyncManager's and
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FMMU's to link the EtherCAT master and the slaves. The IO mapping is done
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automatically, SOEM strives to keep the logical process image as compact as
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possible. It is done by trying to fit Bit oriented slaves together in single
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bytes. Below is an example of 8 slaves and how they are ordered. During
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mapping SOEM also calculates an expected WKC for the IO mapped together.
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That is the primary key to detect errors.
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- Outputs are placed together in the beginning of the IOmap
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- Inputs follow
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When the mapping is done SOEM requests slaves to enter SAFE_OP.
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\code
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char IOmap[128];
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int usedmem;
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...
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usedmem = ec_config_map(&IOmap);
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if (usedmem <= sizeof(IOmap))
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...
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\endcode
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\image html memory_layout.png "memory layout, mapping between physical and logical"
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\image latex memory_layout.png "memory layout, mapping between physical and logical" width=15cm
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To enter state OP we need to send valid data to outputs. The EtherCAT frame
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handling is split into ec_send_processdata and ec_receive_processdata.
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- ec_send_processdata sends the frame on the NIC and saves the frame on
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the stack for receive to fetch.
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- ec_receive_processdata(EC_TIMEOUTRET) tries to fetch the frames on the
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stack. We send an argument for how long we will try to fetch the frame.
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ec_receive_processdata returns the working counter.
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\code
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/* send one valid process data to make outputs in slaves happy*/
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ec_send_processdata();
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wkc = ec_receive_processdata(EC_TIMEOUTRET);
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...
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ec_writestate(0);
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/* wait for all slaves to reach OP state */
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ec_statecheck(0, EC_STATE_OPERATIONAL, EC_TIMEOUTSTATE);
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\endcode
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- Now we have a system up and running, all slaves are in state operational.
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\section application Application
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IO data is accessed through the IOmap, the ec_slave struct keep pointers
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to the start byte in the IO map on slave level together with start bit within
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the start byte. This way we can bit mask IO on bit level even though SOEM
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has combined slave data to minimize the frame size to be sent. We'll use
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slave 8 in the picture above as an example. From a printout from ec_slave we
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have the following:
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- Slave:8
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- Name:EL2622
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- Output size: 2bits
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- Input size: 0bits
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- Configured address: 1008
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- Outputs address: 18cf6
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- Inputs address: 0
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- FMMU0 Ls:2 Ll: 1 Lsb:4 Leb:5 Ps:f00 Psb:0 Ty:2 Act:1
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The Outputs address: 18cf6 is the pointer to slave 8's start byte. The FMMU's
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Lsb:4 (LogicalStartBit) = ec_slave.Ostartbit telling us how to mask for the
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individual bits in the combined byte. The same goes for byte addressed slaves,
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but byte slaves only need the byte start address since they are byte aligned,
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the start bit will be 0.
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Some example on how to access different types of data
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Set an output int 16 value when memory alignment needs to be considered,
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arguments is:
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- slave number in ethercat network
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- module index as index internal to the slave in case more than one
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channel
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- value to write
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\code
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#define EL4001_1 2
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...
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void set_output_int16 (uint16 slave_no, uint8 module_index, int16 value)
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{
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uint8 *data_ptr;
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data_ptr = ec_slave[slave_no].outputs;
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/* Move pointer to correct module index*/
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data_ptr += module_index * 2;
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/* Read value byte by byte since all targets can't handle misaligned
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* addresses
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*/
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*data_ptr++ = (value >> 0) & 0xFF;
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*data_ptr++ = (value >> 8) & 0xFF;
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}
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...
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set_output_int16(EL4001_1,0,slave_EL4001_1.out1);
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\endcode
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Target can handle non aligned pointers to the IOmap
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\code
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typedef struct PACKED
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{
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int16 outvalue1;
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int16 outvalue2;
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} out_EL4132t;
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out_EL4132t *out_EL4132;
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...
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/* connect struct pointers to slave I/O pointers */
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out_EL4132 = (out_EL4132t*) ec_slave[3].outputs;
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out_EL4132->outvalue2 = 0x3FFF;
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...
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\endcode
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Identify and manage errors. The key is the Working Counter, CRC errors
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and errors local to the slave causing a state change can be detected by loss
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of Working Counter since the syncmanagers won't get updated. When returning
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Working Counter don't match Expected Working Counter something is wrong, then it
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is up to an error handler to act, locate the erroneous slave and decide what action
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to perform. The error may not be fatal. Some basic code from simple_test.
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\code
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wkc = ec_receive_processdata(EC_TIMEOUTRET);
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expectedWKC = (ec_group[0].outputsWKC * 2) + ec_group[0].inputsWKC;
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if( inOP && ((wkc < expectedWKC) || ec_group[currentgroup].docheckstate))
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{
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if (needlf)
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{
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needlf = FALSE;
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printf("\n");
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}
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/* one ore more slaves are not responding */
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ec_group[currentgroup].docheckstate = FALSE;
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ec_readstate();
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for (slave = 1; slave <= ec_slavecount; slave++)
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{
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if ((ec_slave[slave].group == currentgroup) && (ec_slave[slave].state != EC_STATE_OPERATIONAL))
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{
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ec_group[currentgroup].docheckstate = TRUE;
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if (ec_slave[slave].state == (EC_STATE_SAFE_OP + EC_STATE_ERROR))
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{
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printf("ERROR : slave %d is in SAFE_OP + ERROR, attempting ack.\n", slave);
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ec_slave[slave].state = (EC_STATE_SAFE_OP + EC_STATE_ACK);
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ec_writestate(slave);
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}
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else if(ec_slave[slave].state == EC_STATE_SAFE_OP)
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{
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printf("WARNING : slave %d is in SAFE_OP, change to OPERATIONAL.\n", slave);
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ec_slave[slave].state = EC_STATE_OPERATIONAL;
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ec_writestate(slave);
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}
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else if(ec_slave[slave].state > EC_STATE_NONE)
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{
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if (ec_reconfig_slave(slave, EC_TIMEOUTMON))
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{
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ec_slave[slave].islost = FALSE;
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printf("MESSAGE : slave %d reconfigured\n",slave);
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}
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}
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else if(!ec_slave[slave].islost)
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{
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/* re-check state */
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ec_statecheck(slave, EC_STATE_OPERATIONAL, EC_TIMEOUTRET);
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if (ec_slave[slave].state == EC_STATE_NONE)
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{
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ec_slave[slave].islost = TRUE;
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printf("ERROR : slave %d lost\n",slave);
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}
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}
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}
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if (ec_slave[slave].islost)
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{
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if(ec_slave[slave].state == EC_STATE_NONE)
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{
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if (ec_recover_slave(slave, EC_TIMEOUTMON))
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{
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ec_slave[slave].islost = FALSE;
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printf("MESSAGE : slave %d recovered\n",slave);
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}
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}
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else
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{
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ec_slave[slave].islost = FALSE;
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printf("MESSAGE : slave %d found\n",slave);
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}
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}
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}
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if(!ec_group[currentgroup].docheckstate)
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printf("OK : all slaves resumed OPERATIONAL.\n");
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}
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\endcode
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This tutorial is just one way of doing it.
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Enjoy and happy coding!
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Andreas Karlsson, rt-labs AB, www.rt-labs.com
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*/
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