ardupilot/libraries/AP_RSSI/AP_RSSI.cpp

/*
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <AP_RSSI/AP_RSSI.h>
#include <AP_BoardConfig/AP_BoardConfig.h>
#include <RC_Channel/RC_Channel.h>
#include <utility>
#include <board_config.h>

extern const AP_HAL::HAL& hal;

#ifdef CONFIG_ARCH_BOARD_PX4FMU_V4
#define BOARD_RSSI_DEFAULT 1
#define BOARD_RSSI_ANA_PIN 11
#define BOARD_RSSI_ANA_PIN_HIGH 3.3f
#else
#define BOARD_RSSI_DEFAULT 0
#define BOARD_RSSI_ANA_PIN 0
#define BOARD_RSSI_ANA_PIN_HIGH 5.0f
#endif

AP_RSSI::PWMState AP_RSSI::pwm_state;

const AP_Param::GroupInfo AP_RSSI::var_info[] = {

    // @Param: TYPE
    // @DisplayName: RSSI Type
    // @Description: Radio Receiver RSSI type. If your radio receiver supports RSSI of some kind, set it here, then set its associated RSSI_XXXXX parameters, if any.
    // @Values: 0:Disabled,1:AnalogPin,2:RCChannelPwmValue,3:ReceiverProtocol,4:PWMInputPin
    // @User: Standard
    AP_GROUPINFO_FLAGS("TYPE", 0, AP_RSSI, rssi_type,  BOARD_RSSI_DEFAULT, AP_PARAM_FLAG_ENABLE),

    // @Param: ANA_PIN
    // @DisplayName: Receiver RSSI sensing pin
    // @Description: pin used to read the RSSI voltage or pwm value
    // @Values: 0:APM2 A0,1:APM2 A1,13:APM2 A13,11:Pixracer,13:Pixhawk ADC4,14:Pixhawk ADC3,15:Pixhawk ADC6,15:Pixhawk2 ADC,50:PixhawkAUX1,51:PixhawkAUX2,52:PixhawkAUX3,53:PixhawkAUX4,54:PixhawkAUX5,55:PixhawkAUX6,103:Pixhawk SBUS
    // @User: Standard
    AP_GROUPINFO("ANA_PIN", 1, AP_RSSI, rssi_analog_pin,  BOARD_RSSI_ANA_PIN),

    // @Param: PIN_LOW
    // @DisplayName: RSSI pin's lowest voltage
    // @Description: RSSI pin's voltage received on the RSSI_ANA_PIN when the signal strength is the weakest. Some radio receivers put out inverted values so this value may be higher than RSSI_PIN_HIGH
    // @Units: V
    // @Increment: 0.01
    // @Range: 0 5.0
    // @User: Standard
    AP_GROUPINFO("PIN_LOW", 2, AP_RSSI, rssi_analog_pin_range_low, 0.0f),

    // @Param: PIN_HIGH
    // @DisplayName: RSSI pin's highest voltage
    // @Description: RSSI pin's voltage received on the RSSI_ANA_PIN when the signal strength is the strongest. Some radio receivers put out inverted values so this value may be lower than RSSI_PIN_LOW
    // @Units: V
    // @Increment: 0.01
    // @Range: 0 5.0
    // @User: Standard
    AP_GROUPINFO("PIN_HIGH", 3, AP_RSSI, rssi_analog_pin_range_high, BOARD_RSSI_ANA_PIN_HIGH),

    // @Param: CHANNEL
    // @DisplayName: Receiver RSSI channel number
    // @Description: The channel number where RSSI will be output by the radio receiver (5 and above).
    // @Range: 0 16
    // @User: Standard
    AP_GROUPINFO("CHANNEL", 4, AP_RSSI, rssi_channel,  0),

    // @Param: CHAN_LOW
    // @DisplayName: RSSI PWM low value
    // @Description: PWM value that the radio receiver will put on the RSSI_CHANNEL or RSSI_ANA_PIN when the signal strength is the weakest. Some radio receivers output inverted values so this value may be lower than RSSI_CHAN_HIGH
    // @Units: PWM
    // @Range: 0 2000
    // @User: Standard
    AP_GROUPINFO("CHAN_LOW", 5, AP_RSSI, rssi_channel_low_pwm_value,  1000),

    // @Param: CHAN_HIGH
    // @DisplayName: Receiver RSSI PWM high value
    // @Description: PWM value that the radio receiver will put on the RSSI_CHANNEL or RSSI_ANA_PIN when the signal strength is the strongest. Some radio receivers output inverted values so this value may be higher than RSSI_CHAN_LOW
    // @Units: PWM
    // @Range: 0 2000
    // @User: Standard
    AP_GROUPINFO("CHAN_HIGH", 6, AP_RSSI, rssi_channel_high_pwm_value,  2000),

    AP_GROUPEND
};

// Public
// ------

// constructor
AP_RSSI::AP_RSSI()
{       
    AP_Param::setup_object_defaults(this, var_info);
    if (_s_instance) {
        AP_HAL::panic("Too many RSSI sensors");
    }
    _s_instance = this;
}

// destructor
AP_RSSI::~AP_RSSI(void)
{       
}

/*
 * Get the AP_RSSI singleton
 */
AP_RSSI *AP_RSSI::get_instance()
{
    return _s_instance;
}

// Initialize the rssi object and prepare it for use
void AP_RSSI::init()
{
    // a pin for reading the receiver RSSI voltage. The scaling by 0.25 
    // is to take the 0 to 1024 range down to an 8 bit range for MAVLink    
    rssi_analog_source = hal.analogin->channel(ANALOG_INPUT_NONE);    
}

// Read the receiver RSSI value as a float 0.0f - 1.0f.
// 0.0 represents weakest signal, 1.0 represents maximum signal.
float AP_RSSI::read_receiver_rssi()
{
    // Default to 0 RSSI
    float receiver_rssi = 0.0f;  

    switch (rssi_type) {
        case RssiType::RSSI_DISABLED:
            receiver_rssi = 0.0f;
            break;
        case RssiType::RSSI_ANALOG_PIN:
            receiver_rssi = read_pin_rssi();
            break;
        case RssiType::RSSI_RC_CHANNEL_VALUE:
            receiver_rssi = read_channel_rssi();
            break;
        case RssiType::RSSI_RECEIVER: {
            int16_t rssi = RC_Channels::get_receiver_rssi();
            if (rssi != -1) {
                receiver_rssi = rssi / 255.0;
            }
            break;
        }
        case RssiType::RSSI_PWM_PIN:
            receiver_rssi = read_pwm_pin_rssi();
            break;
        default :   
            receiver_rssi = 0.0f;
            break;
    }    
                  
    return receiver_rssi;
}

// Read the receiver RSSI value as an 8-bit integer
// 0 represents weakest signal, 255 represents maximum signal.
uint8_t AP_RSSI::read_receiver_rssi_uint8()
{
    return read_receiver_rssi() * 255; 
}

// Private
// -------

// read the RSSI value from an analog pin - returns float in range 0.0 to 1.0
float AP_RSSI::read_pin_rssi()
{
    rssi_analog_source->set_pin(rssi_analog_pin);
    float current_analog_voltage = rssi_analog_source->voltage_average();

    return scale_and_constrain_float_rssi(current_analog_voltage, rssi_analog_pin_range_low, rssi_analog_pin_range_high);
}

// read the RSSI value from a PWM value on a RC channel
float AP_RSSI::read_channel_rssi()
{
    uint16_t rssi_channel_value = RC_Channels::get_radio_in(rssi_channel-1);
    float channel_rssi = scale_and_constrain_float_rssi(rssi_channel_value, rssi_channel_low_pwm_value, rssi_channel_high_pwm_value);
    return channel_rssi;    
}

// read the PWM value from a pin
float AP_RSSI::read_pwm_pin_rssi()
{
#if CONFIG_HAL_BOARD == HAL_BOARD_PX4 || CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
    // check if pin has changed and initialise gpio event callback
    pwm_state.gpio = get_gpio(rssi_analog_pin);
    if (pwm_state.gpio != pwm_state.last_gpio) {

        // remove old gpio event callback if present
        if (pwm_state.last_gpio != 0) {
            stm32_gpiosetevent(pwm_state.last_gpio, false, false, false, nullptr);
            pwm_state.last_gpio = 0;
        }

        // install interrupt handler on rising or falling edge of gpio
        if (pwm_state.gpio != 0) {
            stm32_gpiosetevent(pwm_state.gpio, true, true, false, irq_handler);
            pwm_state.last_gpio = pwm_state.gpio;
        }
    }

    // disable interrupts temporarily
    irqstate_t istate = irqsave();

    // check for timeout
    float ret;
    if ((pwm_state.last_reading_ms == 0) || (AP_HAL::millis() - pwm_state.last_reading_ms > 1000)) {
        pwm_state.value = 0;
        ret = 0;
    } else {
        // convert pwm value to rssi value
        ret = scale_and_constrain_float_rssi(pwm_state.value, rssi_channel_low_pwm_value, rssi_channel_high_pwm_value);
    }

    // restore interrupts
    irqrestore(istate);

    return ret;
#else
    return 0.0f;
#endif
}

// Scale and constrain a float rssi value to 0.0 to 1.0 range 
float AP_RSSI::scale_and_constrain_float_rssi(float current_rssi_value, float low_rssi_range, float high_rssi_range)
{    
    float rssi_value_range = fabsf(high_rssi_range - low_rssi_range);
    if (is_zero(rssi_value_range)) {
        // User range isn't meaningful, return 0 for RSSI (and avoid divide by zero)
        return 0.0f;   
    }
    // Note that user-supplied ranges may be inverted and we accommodate that here. 
    // (Some radio receivers put out inverted ranges for RSSI-type values).    
    bool range_is_inverted = (high_rssi_range < low_rssi_range);
    // Constrain to the possible range - values outside are clipped to ends 
    current_rssi_value = constrain_float(current_rssi_value, 
                                        range_is_inverted ? high_rssi_range : low_rssi_range, 
                                        range_is_inverted ? low_rssi_range : high_rssi_range);    

    if (range_is_inverted)
    {
        // Swap values so we can treat them as low->high uniformly in the code that follows
        current_rssi_value = high_rssi_range + fabsf(current_rssi_value - low_rssi_range);
        std::swap(low_rssi_range, high_rssi_range);        
    }

    // Scale the value down to a 0.0 - 1.0 range
    float rssi_value_scaled = (current_rssi_value - low_rssi_range) / rssi_value_range;
    // Make absolutely sure the value is clipped to the 0.0 - 1.0 range. This should handle things if the
    // value retrieved falls outside the user-supplied range.
    return constrain_float(rssi_value_scaled, 0.0f, 1.0f);
}

// get gpio id from pin number
uint32_t AP_RSSI::get_gpio(uint8_t pin_number)
{
#ifdef GPIO_GPIO0_INPUT
    switch (pin_number) {
    case 50:
        return GPIO_GPIO0_INPUT;
    case 51:
        return GPIO_GPIO1_INPUT;
    case 52:
        return GPIO_GPIO2_INPUT;
    case 53:
        return GPIO_GPIO3_INPUT;
    case 54:
        return GPIO_GPIO4_INPUT;
    case 55:
        return GPIO_GPIO5_INPUT;
    }
#endif
    return 0;
}

// interrupt handler for reading pwm value
int AP_RSSI::irq_handler(int irq, void *context)
{
#if CONFIG_HAL_BOARD == HAL_BOARD_PX4 || CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
    // sanity check
    if (pwm_state.gpio == 0) {
        return 0;
    }

    // capture time
    uint64_t now = AP_HAL::micros64();

    // read value of pin
    bool pin_high = stm32_gpioread(pwm_state.gpio);

    // calculate pwm value
    if (pin_high) {
        pwm_state.pulse_start_us = now;
    } else {
        if (pwm_state.pulse_start_us != 0) {
            pwm_state.value = now - pwm_state.pulse_start_us;
        }
        pwm_state.pulse_start_us = 0;
        pwm_state.last_reading_ms = AP_HAL::millis();
    }
#endif

    return 0;
}

AP_RSSI *AP_RSSI::_s_instance = nullptr;

namespace AP {

AP_RSSI *rssi()
{
    return AP_RSSI::get_instance();
}

};