ardupilot/libraries/AP_BattMonitor/AP_BattMonitor_FuelFlow.cpp

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#include <AP_HAL/AP_HAL.h>
#include "AP_BattMonitor_FuelFlow.h"
#include <GCS_MAVLink/GCS.h>
/*
"battery" monitor for liquid fuel flow systems that give a pulse on
a pin for fixed volumes of fuel.
this driver assumes that BATTx_AMP_PERVLT is set to give the
number of millilitres per pulse.
Output is:
- current in Amps maps to in litres/hour
- consumed mAh is in consumed millilitres
- fixed 1.0v voltage
*/
extern const AP_HAL::HAL& hal;
#define FUELFLOW_MIN_PULSE_DELTA_US 10
/// Constructor
AP_BattMonitor_FuelFlow::AP_BattMonitor_FuelFlow(AP_BattMonitor &mon,
AP_BattMonitor::BattMonitor_State &mon_state,
AP_BattMonitor_Params &params) :
AP_BattMonitor_Backend(mon, mon_state, params)
{
_state.voltage = 1.0; // show a fixed voltage of 1v
// we can't tell if it is healthy as we expect zero pulses when no
// fuel is flowing
_state.healthy = true;
}
/*
handle interrupt on an instance
*/
void AP_BattMonitor_FuelFlow::irq_handler(uint8_t pin, bool pin_state, uint32_t timestamp)
{
if (irq_state.last_pulse_us == 0) {
irq_state.last_pulse_us = timestamp;
return;
}
uint32_t delta = timestamp - irq_state.last_pulse_us;
if (delta < FUELFLOW_MIN_PULSE_DELTA_US) {
// simple de-bounce
return;
}
irq_state.pulse_count++;
irq_state.total_us += delta;
irq_state.last_pulse_us = timestamp;
}
/*
read - read the "voltage" and "current"
*/
void AP_BattMonitor_FuelFlow::read()
{
int8_t pin = _params._curr_pin;
if (last_pin != pin) {
// detach from last pin
if (last_pin != -1) {
hal.gpio->detach_interrupt(last_pin);
}
// attach to new pin
last_pin = pin;
if (last_pin > 0) {
hal.gpio->pinMode(last_pin, HAL_GPIO_INPUT);
if (!hal.gpio->attach_interrupt(
last_pin,
FUNCTOR_BIND_MEMBER(&AP_BattMonitor_FuelFlow::irq_handler, void, uint8_t, bool, uint32_t),
AP_HAL::GPIO::INTERRUPT_RISING)) {
gcs().send_text(MAV_SEVERITY_WARNING, "FuelFlow: Failed to attach to pin %u", last_pin);
}
}
}
uint32_t now_us = AP_HAL::micros();
if (_state.last_time_micros == 0) {
// need initial time, so we can work out expected pulse rate
_state.last_time_micros = now_us;
return;
}
float dt = (now_us - _state.last_time_micros) * 1.0e-6f;
if (dt < 1 && irq_state.pulse_count == 0) {
// we allow for up to 1 second with no pulses to cope with low
// flow idling. After that we will start reading zero current
return;
}
// get the IRQ state with interrupts disabled
struct IrqState state;
void *irqstate = hal.scheduler->disable_interrupts_save();
state = irq_state;
irq_state.pulse_count = 0;
irq_state.total_us = 0;
hal.scheduler->restore_interrupts(irqstate);
/*
this driver assumes that BATTx_AMP_PERVLT is set to give the
number of millilitres per pulse.
*/
float irq_dt = state.total_us * 1.0e-6f;
float litres, litres_pec_sec;
if (state.pulse_count == 0) {
litres = 0;
litres_pec_sec = 0;
} else {
litres = state.pulse_count * _params._curr_amp_per_volt * 0.001f;
litres_pec_sec = litres / irq_dt;
}
_state.last_time_micros = now_us;
// map amps to litres/hour
_state.current_amps = litres_pec_sec * (60*60);
// map consumed_mah to consumed millilitres
_state.consumed_mah += litres * 1000;
// map consumed_wh using fixed voltage of 1
_state.consumed_wh = _state.consumed_mah;
}