SOURCES = main.c system/usbd_conf.c system/usbd_cdc_if.c system/usb_device.c system/usbd_desc.c system/interrupts.c system/system_stm32f0xx.c gpio.c spi.c ssd1306.c stringhelpers.c display.c system/syslib.c storage.c flash.c max31855.c max31865.c

// Globalish setting vars

static __IO uint32_t TimingDelay;

        process();

// PID implementation

// TODO: Make struct that has the last_temp and i_state in it, pass by ref. Make struct that has other input values maybe.

int16_t last_pid_temp = 0;

uint8_t last_pid_temp_frac = 0;

int32_t i_state = 0;

int16_t update_pid(uint16_t k_p, uint16_t k_i, uint16_t k_d, int16_t temp, uint8_t temp_frac, int16_t setpoint) 

{

  // Calculate instantaneous error

  int16_t error = setpoint - temp; // TODO: Use fixed point fraction

  // Proportional component

  int32_t p_term = k_p * error;

  // Error accumulator (integrator)

  i_state += error;

  // to prevent the iTerm getting huge from lots of 

  //  error, we use a "windup guard" 

  // (this happens when the machine is first turned on and

  // it cant help be cold despite its best efforts)

  // not necessary, but this makes windup guard values 

  // relative to the current iGain

  int32_t windup_guard_res = set.val.windup_guard / k_i;  

  // Calculate integral term with windup guard 

  if (i_state > windup_guard_res) 

    i_state = windup_guard_res;

  else if (i_state < -windup_guard_res) 

    i_state = -windup_guard_res;

  int32_t i_term = k_i * i_state;

  // Calculate differential term (slope since last iteration)

  int32_t d_term = (k_d * (status.temp - last_pid_temp));

  // Save temperature for next iteration

  last_pid_temp = status.temp;

  last_pid_temp_frac = status.temp_frac;

  int16_t result = p_term + i_term - d_term;

  // Put out tenths of percent, 0-1000. 

  if(result > 1000)

    result = 1000;

  else if(result < -1000)

    result = -1000;

  // Return feedback

  return result;

}

uint32_t last_ssr_on = 0;

uint32_t last_vcp_tx = 0;

uint32_t last_led = 0;

uint32_t last_pid = 0;

int16_t ssr_output = 0; // Duty cycle of ssr, 0 to SSR_PERIOD 

// Turn SSR output on/off according to set duty cycle.

// TODO: Eventually maybe replace with a very slow timer or something. Double-check this code...

void process()

{

    uint32_t ticks = HAL_GetTick();

    if(ticks - last_led > 400) 

    {

        last_led = ticks;

    }

    if((ticks - last_pid > PID_PERIOD))

    {

        #ifdef MAX31855_TC_SENSOR

        max31855_readtemp(spi_get(), &set, &status); // Read MAX31855

        #endif

        #ifdef MAX31865_RTD_SENSOR

        max31865_readtemp(&set, &status);

        #endif

    HAL_GPIO_TogglePin(LED_POWER);

        if(status.pid_enabled) 

        {

            // Get ssr output for next time

            int16_t power_percent = update_pid(set.val.k_p, set.val.k_i, set.val.k_d, status.temp, status.temp_frac, status.setpoint);

            //power-percent is 0-1000

            ssr_output = power_percent; //(((uint32_t)SSR_PERIOD * (uint32_t)10 * (uint32_t)100) * power_percent) / (uint32_t)1000000;

        }

        else 

        {

            ssr_output = 0;

        }

        last_pid = ticks;

    }

    // Every 200ms, set the SSR on unless output is 0

    if((ticks - last_ssr_on > SSR_PERIOD))

    {

        // Only support heating (ssr_output > 0) right now

        if(ssr_output > 0) {

            char tempstr[6];

            itoa(ssr_output, tempstr, 10);

            ssd1306_DrawString(tempstr, 0, 90);

            HAL_GPIO_WritePin(SSR_PIN, 1);

            last_ssr_on = ticks;

        }

    }

    // Kill SSR after elapsed period less than SSR_PERIOD 

    if(ticks - last_ssr_on > ssr_output || ssr_output == 0)

    {

        HAL_GPIO_WritePin(SSR_PIN, 0);

    }

    if(ticks - last_vcp_tx > VCP_TX_FREQ)

    {

        // Print temp to cdc

        char tempstr[16];

        itoa_fp(status.temp, status.temp_frac, tempstr);

        uint8_t numlen = strlen(tempstr);

        tempstr[numlen] = '\r';

        tempstr[numlen+1] = '\n';

//        if(set.val.usb_plugged)

//            CDC_Transmit_FS(tempstr, numlen+2);

       // while(CDC_Transmit_FS("\r\n", 2) == USBD_BUSY);

        last_vcp_tx = ticks;

    }

}