beremiz

Better jitter compensation before sending Ethercat frame. Jitter can be compensed in both directions, within some limits

2012-09-21, Edouard Tisserant
22e9993348f6
Parents 21eb91dc7071
Children 7d0ebbff1d08
Better jitter compensation before sending Ethercat frame. Jitter can be compensed in both directions, within some limits
1 files changed, 27 insertions(+), 15 deletions(-)
  • +27 -15
    etherlab/plc_etherlab.c
    • --- a/etherlab/plc_etherlab.c Wed Sep 19 03:30:58 2012 +0200
    +++ b/etherlab/plc_etherlab.c Fri Sep 21 16:02:33 2012 +0200
    @@ -122,12 +122,6 @@
    void __retrieve_%(location)s(void)
    {
    -// // send process data
    -// ecrt_rtdm_domain_queque(rt_fd);
    -// ecrt_rtdm_master_send(rt_fd);
    -//
    -// rt_task_sleep(rt_timer_ns2tsc(wait_period_ns));
    -
    // receive ethercat
    if(first_sent){
    ecrt_rtdm_master_recieve(rt_fd);
    @@ -138,22 +132,40 @@
    }
    static RTIME _last_occur=0;
    +static RTIME _last_publish=0;
    RTIME _current_lag=0;
    +RTIME _max_jitter=0;
    +static inline RTIME max(RTIME a,RTIME b){return a>b?a:b;}
    void __publish_%(location)s(void)
    {
    %(publish_variables)s
    ecrt_rtdm_domain_queque(rt_fd);
    {
    - RTIME _current_time = rt_timer_read();
    - RTIME deadline = _last_occur ?
    - _last_occur + common_ticktime__:
    - _current_time;
    - _last_occur = _current_time;
    - _current_lag = deadline - _current_time;
    - while(_current_time < deadline) {
    - _last_occur = _current_time;
    - _current_time = rt_timer_read();
    + RTIME current_time = rt_timer_read();
    + // Limit spining max 1/5 of common_ticktime
    + RTIME maxdeadline = current_time + (common_ticktime__ / 5);
    + RTIME deadline = _last_occur ?
    + _last_occur + common_ticktime__ :
    + current_time + _max_jitter;
    + if(deadline > maxdeadline) deadline = maxdeadline;
    + _current_lag = deadline - current_time;
    + if(_last_publish != 0){
    + RTIME period = current_time - _last_publish;
    + if(period > common_ticktime__ )
    + _max_jitter = max(_max_jitter, period - common_ticktime__);
    + else
    + _max_jitter = max(_max_jitter, common_ticktime__ - period);
    + }
    + _last_publish = current_time;
    + _last_occur = current_time;
    + while(current_time < deadline) {
    + _last_occur = current_time; //Drift backward by default
    + current_time = rt_timer_read();
    + }
    + if( _max_jitter * 10 < common_ticktime__ && _current_lag < _max_jitter){
    + //Consuming security margin ?
    + _last_occur = current_time; //Drift forward
    }
    }
    ecrt_rtdm_master_send(rt_fd);