[Etherlab-users] ecrt_sdo_request_state : error

[BUSSIERES Vincent]

Dear Etherlab users,

I use a Beckhoff module EL5102 (2 channels encoder interface) and two servodrives to control motors.

I develop a homing sequence as below :

1- Enable counter reset on channel 1 when index encoder is encountered
2- Move axis 1 until index is encoutered
3- Unable counter reset on channel 1
4- Enable counter reset on channel 2 when index encoder is encountered
5- Move axis 2 until index is encoutered
6- Unable counter reset on channel 2

Unabling and disabling counter reset is done using SDOs 0x80n0:01 where n is the channel number.

In my program, I create 2 SDO requests with « ecrt_slave_config_create_sdo_request » before changing master state in OP with « ecrt_master_activate ».
Then, before entering in cyclic task, I write SDOs for the first time and I get « EC_REQUEST_UNUSED » SDO request state (trigger first write), it seems to be OK.

void enableIndexResetCh_n(state)
{
        switch (ecrt_sdo_request_state(mReqIndexResetCh_n)) {
                case EC_REQUEST_UNUSED:
                    ecrt_sdo_request_write(mReqIndexResetCh_n);
                    break;

                case EC_REQUEST_BUSY:
                    break;

                case EC_REQUEST_SUCCESS:
                    EC_WRITE_U8(ecrt_sdo_request_data(mReqIndexResetCh1), static_cast<uint8_t>(state));
                    ecrt_sdo_request_write(mReqIndexResetCh_n);
                    break;

                default:
                    ecrt_sdo_request_write(mReqIndexResetCh_n);
                    break;
                }
                break;
}

Then, I realize homing sequence in the cyclic task as described before.
For the fisrt channel, I write « 1 » into SDO 0x8000:01, request state is « EC_REQUEST_SUCCES » but for the second channel 0x8010:02 I get « EC_REQUEST_ERROR » and SDO value remains at false state.
I don’t understand why I get this error.

Moreover I want to let you know that I don’t call « ecrt_sdo_request_write » at each loop of cyclic task but only when I need to change sdo state. Perhaps this is not the right way to call this function. Do I have to call this function at each iteration ?
How can I be sure that sdo state corresponds to the right state ? Do I have to read sdo state (if sdo is R/W) also at each iteration ?

Regards
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