File content as of revision 34:294adcc3e4b2:

/*------------------------------------------------------------------------------
Library code file for interface to Heater
Date: 16/07/2018


------------------------------------------------------------------------------*/
#include "mbed.h"
#include "MODSERIAL.h"
#include "Heater.h"
#include "ADS8568_ADC.h"

Heater::Heater(const int i_port, const int v_port, FastPWM * drive, FastPWM * guard, ADS8568_ADC * adc, DigitalIn adc_busy, const memspcr_ThermalConfiguration & thermal)
    :thermal(thermal), i_port(i_port), v_port(v_port), drive(drive), guard(guard), adc(adc), adc_busy(adc_busy)
{
    drive->prescaler(1);
    guard->prescaler(1);
    drive->period_ticks(1000);
    guard->period_ticks(1000);
}

void Heater::read()
{
    //Reads R and then resets the drive back to its previous value
    int i = 0;
    float drive_cal[2] = {0.0, 10.0};       // replace with drive cal passed via Heater class
    double drive_prev = drive->read();     //Store previous value of drive
    *drive = 1.0f;                         //Turn the driver on for the measurement
    wait_us(thermal.settling_time_us);     //Wait for ADC to settle
    adc->start_conversion(ADC_CONV_ALL_CH);     
    
    //Incremental back off until ADC is free
    while(adc_busy == 1) {
        wait_us(1);
        i++;
    }

    drive->write(0);       //Reset the duty cycle back to what it was

    //Get voltage, current and R values from the ADC conversion
    adc->read_channels();
    curr = adc->read_channel_result(i_port);
    v = adc->read_channel_result(v_port);

    if (curr > 0) {
        R = (float)v/curr;                //Avoid dividing by 0
        R = drive_cal[0] + drive_cal[1]*R;  //Convert to Ohms
    }

    //Get error values
    error = R_ref - R;

    //Only allow positive integrated errors and limit change in integrated error
    //to help avoid integral windup

    if (abs(error) > thermal.pid_wind_up_limit_ohm) {error = error * thermal.pid_wind_up_limit_ohm / abs(error);}
    
    error_integrated += error;

    if (error_integrated < 0.0) {
        error_integrated = 0.0;
    }
}

void Heater::update()
{
    //Update PWM from setpoint and resistance
    double duty_cycle = (double) thermal.pid_kp_mho * (error + error_integrated/thermal.pid_integral_time_ms);
    if (duty_cycle > thermal.pid_pwm_limit) duty_cycle = thermal.pid_pwm_limit;
    drive->write(duty_cycle);
    guard->write(duty_cycle * thermal.guard_drive_ratio);
}

void Heater::Set_ref(float R)
{
    R_ref = R;
}
void Heater::Set_D(float D)
{
    drive->write(D);
    guard->write(D*thermal.guard_drive_ratio);
}

int Heater::Get_D() const
{
    return drive->read();
}

int Heater::Get_i() const
{
    return curr;
}
int Heater::Get_v() const
{
    return v;
}

float Heater::Get_R() const
{
    return R;
}

float Heater::Get_R_ref() const
{
    return R_ref;
}

float Heater::Get_error() const
{
    return error;
}

float Heater::Get_error_integrated() const
{
    return error_integrated;
}

void Heater::turn_on ()
{
    *drive = 1;
    *guard = thermal.guard_drive_ratio;
}

void Heater::turn_off ()
{
    *drive = 0;
    *guard = 0;
}