failsafe.pde
The failsafe.pde file contains functions and variables needed for failsafe strategy, that consist on detecting main loop lockup.
// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
failsafe support
Andrew Tridgell, December 2011
*/
/*
our failsafe strategy is to detect main loop lockup and switch to
passing inputs straight from the RC inputs to RC outputs.
*/
/*
this failsafe_check function is called from the core timer interrupt
at 1kHz.
*/
...
Here is the intro and use recommendations.
static void failsafe_check()
{
static uint16_t last_mainLoop_count;
static uint32_t last_timestamp;
static bool in_failsafe;
uint32_t tnow = hal.scheduler->micros();
...
The file starts with the definition of the failsafe_check
function and the definition of some internal variables of these function.
if (mainLoop_count != last_mainLoop_count) {
// the main loop is running, all is OK
last_mainLoop_count = mainLoop_count;
last_timestamp = tnow;
in_failsafe = false;
return;
}
...
This slice of code checks if the main loop is running and there is no lockup.
if (tnow - last_timestamp > 200000) {
// we have gone at least 0.2 seconds since the main loop
// ran. That means we're in trouble, or perhaps are in
// an initialisation routine or log erase. Start passing RC
// inputs through to outputs
in_failsafe = true;
}
...
If the (tnow-last_timestamp) value is greater than 200 ms, there is a lockup. The RC inputs are passed to the outputs.
if (in_failsafe && tnow - last_timestamp > 20000 &&
channel_throttle->read() >= (uint16_t)g.fs_throttle_value) {
// pass RC inputs to outputs every 20ms
last_timestamp = tnow;
hal.rcin->clear_overrides();
uint8_t start_ch = 0;
for (uint8_t ch=start_ch; ch<4; ch++) {
hal.rcout->write(ch, hal.rcin->read(ch));
}
RC_Channel_aux::copy_radio_in_out(RC_Channel_aux::k_manual, true);
}
}
If in adition to the value greater than 200 ms the channel_throttle
is greater then the fs_throttle_value
RC inputs are passed to outputs every 20 ms; also the overlays are erased.