Embedded TCP/IP stack: fnet_timer_poll

SW Timer polling function.

See also

FNET_CFG_TIMER_POLL_AUTOMATIC

This function checks timeouts for TCP, ARP, IP and other stack activities.
The user application should call this function periodically, after the FNET stack initialization, and only if FNET_CFG_TIMER_POLL_AUTOMATIC is 0.
Recommended polling period is 100ms or less.
If FNET_CFG_TIMER_POLL_AUTOMATIC is 1, this function is called automatically by FNET in HW interrupt.