Changeset - 8a3e6f39733b
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Ethan Zonca - 10 years ago 2014-08-26 22:57:39
ez@ethanzonca.com
Initial PID implementation functional
1 file changed with 77 insertions and 6 deletions:
main.c
77
6
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main.c
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#include "main.h"
 
#include "stm32l100c_discovery.h"
 
#include "ssd1306.h"
 
#include "config.h"
 
 
// USB includes
 
#include "hw_config.h"
 
#include "usb_lib.h"
 
#include "usb_desc.h"
 
#include "usb_pwr.h"
 
#include "stringhelpers.h"
 
 
// TODO: Grab buttonpresses with interrupts
 
// TODO: Eliminate screen buffer since we aren't using it...
 
 
// USB Supporting Vars
 
extern __IO uint8_t Receive_Buffer[64];
 
extern __IO  uint32_t Receive_length ;
 
extern __IO  uint32_t length ;
 
uint8_t Send_Buffer[64];
 
uint32_t packet_sent=1;
 
uint32_t packet_receive=1;
 
 
// State definition
 
enum state {
 
    STATE_IDLE = 0,
 
 
    STATE_SETP,
 
    STATE_SETI,
 
    STATE_SETD,
 
 
    STATE_PREHEAT_BREW,
 
    STATE_MAINTAIN_BREW,
 
    STATE_PREHEAT_STEAM,
 
    STATE_MAINTAIN_STEAM,
 
};
 
 
 
static __IO uint32_t TimingDelay;
 
 
// Move to header file
 
void init_gpio();
 
void init_spi();
 
void process();
 
void machine();
 
void delay(__IO uint32_t nTime);
 
 
int main(void)
 
{
 
 
    // Init clocks
 
    SystemInit();
 
 
    // Init GPIO
 
    init_gpio();
 
 
    // Init USB
 
    //Set_USBClock();
 
    //USB_Interrupts_Config();
 
    //USB_Init();
 
 
    // Turn on power LED
 
    GPIO_SetBits(LED_POWER);
 
 
    // TODO: Awesome pwm of power LED (TIM4_CH4 or TIM11_CH1)
 
    // TODO: PWM of stat led (TIM3_CH2)
 
 
    // Configure 1ms SysTick (change if more temporal resolution needed)
 
    RCC_ClocksTypeDef RCC_Clocks;
 
    RCC_GetClocksFreq(&RCC_Clocks);
 
    SysTick_Config(RCC_Clocks.HCLK_Frequency / 1000);
 
 
    // Init SPI busses
 
    init_spi();
 
 
    // Init OLED over SPI
 
    ssd1306_Init();
 
    ssd1306_clearscreen();
 
 
    // Startup screen
 
    ssd1306_DrawString("therm v0.1", 1, 40);
 
    ssd1306_DrawString("protofusion.org/therm", 3, 0);
 
    delay(1500);
 
    ssd1306_clearscreen();
 
 
    GPIO_ResetBits(LED_STAT);
 
 
    // Main loop
 
    while(1)
 
    {
 
        // Process sensor inputs
 
        process();
 
 
        // Run state machine
 
        machine();
 
    }
 
}
 
 
 
 
// Read temperature and update global temp vars
 
int16_t temp = 0;
 
uint8_t temp_frac = 0;
 
 
void update_temp() {
 
    // Assert CS
 
    GPIO_ResetBits(MAX_CS);
 
    delay(1);
 
 
    // This may not clock at all... might need to send 16 bits first
 
    SPI_I2S_SendData(SPI2, 0xAAAA); // send dummy data
 
    //SPI_I2S_SendData(SPI2, 0xAA); // send dummy data
 
    uint16_t temp_pre = SPI_I2S_ReceiveData(SPI2);
 
 
    if(temp_pre & 0b0000000000000010) {
 
        ssd1306_DrawString("Fatal Error", 2, 35);
 
    }
 
    else if(temp_pre & 0b0000000000000001) {
 
        ssd1306_DrawString("Error: No TC", 2, 40);
 
        temp = 0;
 
        temp_frac = 0;
 
    }
 
    else
 
    {
 
        uint8_t sign = temp >> 15;// top bit is sign
 
 
        temp_pre = temp_pre >> 2; // Drop 2 lowest bits
 
        temp_frac = temp_pre & 0b11; // get fractional part
 
        temp_frac *= 25; // each bit is .25 a degree, up to fixed point
 
        temp_pre = temp_pre >> 2; // Drop 2 fractional bits
 
 
        if(sign) {
 
            temp = -temp_pre;
 
        }
 
        else {
 
            temp = temp_pre;
 
        }
 
    }
 
 
    // Deassert CS
 
    delay(1);
 
    GPIO_SetBits(MAX_CS);
 
}
 
 
 
// PID implementation
 
int16_t last_pid_temp = 0;
 
uint8_t last_pid_temp_frac = 0;
 
int16_t i_state = 0;
 
#define WINDUP_GUARD_GAIN 100
 
 
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 = (int16_t)setpoint - (int16_t)temp; // TODO: Use fixed point fraction
 
 
  // Proportional component
 
  int16_t p_term = k_p * error;
 
 
  // Error accumulator (integrator)
 
  i_state += error;
 
 
  // to prevent the iTerm getting huge despite 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
 
  int16_t windup_guard = WINDUP_GUARD_GAIN / k_i;
 
 
  // Calculate integral term with windup guard
 
  if (i_state > windup_guard)
 
    i_state = windup_guard;
 
  else if (i_state < -windup_guard)
 
    i_state = -windup_guard;
 
  int16_t i_term = k_i * i_state;
 
 
  // Calculate differential term (slope since last iteration)
 
  int16_t d_term = (k_d * (temp - last_pid_temp));
 
 
  // Save temperature for next iteration
 
  last_pid_temp = temp;
 
  last_pid_temp_frac = 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 ticks = 0;
 
uint32_t last_ssr_on = 0;
 
uint32_t last_led = 0;
 
int32_t setpoint = 0;
 
uint16_t k_p = 1;
 
uint16_t k_i = 1;
 
uint16_t k_d = 1;
 
uint8_t ssr_output = 0; // Duty cycle of ssr, 0 to SSR_PERIOD
 
int16_t ssr_output = 0; // Duty cycle of ssr, 0 to SSR_PERIOD
 
 
 
// Process things
 
void process()
 
{
 
    update_temp(); // Read MAX31855
 
 
    // TODO: Add calibration offset (linear)
 
 
    if(ticks - last_led > 400)
 
    {
 
        GPIO_ToggleBits(LED_POWER);
 
        last_led = ticks;
 
    }
 
 
    // Every 200ms, set the SSR on unless output is 0
 
    if((ticks - last_ssr_on > SSR_PERIOD) && ssr_output > 0)
 
    if((ticks - last_ssr_on > SSR_PERIOD))
 
    {
 
        GPIO_SetBits(LED_STAT);
 
        last_ssr_on = ticks;
 
        // Get ssr output for next time
 
        int16_t power_percent = update_pid(k_p, k_i, k_d, temp, temp_frac, 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;
 
 
        // Only support heating (ssr_output > 0) right now
 
        if(ssr_output > 0) {
 
 
            char tempstr[6];
 
            itoa(ssr_output, tempstr);
 
            ssd1306_DrawString("#=", 2, 45);
 
            ssd1306_DrawString("    ", 2, 57);
 
            ssd1306_DrawString(tempstr, 2, 57);
 
 
            GPIO_SetBits(LED_STAT);
 
            last_ssr_on = ticks;
 
        }
 
    }
 
 
    // Kill SSR after elapsed period less than SSR_PERIOD
 
    if(ticks - last_ssr_on > ssr_output)
 
    {
 
        GPIO_ResetBits(LED_STAT);
 
    }
 
}
 
 
void draw_setpoint() {
 
    char tempstr[3];
 
    itoa_fp(temp, temp_frac, tempstr);
 
    //ssd1306_DrawString("        ", 3, 40);
 
    ssd1306_DrawString(tempstr, 3, 40);
 
    ssd1306_DrawString("-> ", 3, 80);
 
    itoa(setpoint, tempstr);
 
    ssd1306_DrawString("    ", 3, 95);
 
    ssd1306_DrawString(tempstr, 3, 95);
 
}
 
 
uint8_t state = STATE_IDLE;
 
uint8_t goto_mode = 2;
 
 
// State machine
 
uint8_t sw_btn_last = 0;
 
uint8_t sw_up_last = 0;
 
uint8_t sw_down_last = 0;
 
uint8_t sw_left_last = 0;
 
uint8_t sw_right_last = 0;
 
 
#define SW_BTN_PRESSED (sw_btn_last == 0 && sw_btn == 1) // rising edge on buttonpress
 
#define SW_UP_PRESSED (sw_up_last == 0 && sw_up == 1)
 
#define SW_DOWN_PRESSED (sw_down_last == 0 && sw_down == 1)
 
#define SW_LEFT_PRESSED (sw_left_last == 0 && sw_left == 1)
 
#define SW_RIGHT_PRESSED (sw_right_last == 0 && sw_right == 1)
 
 
void machine()
 
{
 
    uint8_t last_state = state;
 
 
    uint8_t sw_btn = !GPIO_ReadInputDataBit(SW_BTN);
 
    uint8_t sw_up = !GPIO_ReadInputDataBit(SW_UP);
 
    uint8_t sw_down = !GPIO_ReadInputDataBit(SW_DOWN);
 
    uint8_t sw_left = !GPIO_ReadInputDataBit(SW_LEFT);
 
    uint8_t sw_right = !GPIO_ReadInputDataBit(SW_RIGHT);
 
 
    switch(state)
 
    {
 
        // Idle state
 
        case STATE_IDLE:
 
        {
 
            // Write text to OLED
 
            // [ therm :: idle ]
 
            ssd1306_DrawString("therm :: idle ", 0, 40);
 
 
            char tempstr[6];
 
            itoa_fp(temp, temp_frac, tempstr);
 
            ssd1306_DrawString("Temp: ", 3, 40);
 
            ssd1306_DrawString("    ", 3, 70);
 
            ssd1306_DrawString(tempstr, 3, 72);
 
 
            ssd1306_drawlogo();
 
 
            switch(goto_mode) {
 
                case 2:
 
                {
 
                    ssd1306_DrawString("-> brew     ", 1, 40);
 
                } break;
 
 
                case 1:
 
                {
 
                    ssd1306_DrawString("-> set P/I/D", 1, 40);
 
                } break;
 
 
                case 0:
 
                {
 
                    ssd1306_DrawString("-> setup    ", 1, 40);
 
                } break;
 
            }
 
 
            // Button handler
 
            if(SW_BTN_PRESSED) {
 
                switch(goto_mode) {
 
                    case 2:
 
                        state = STATE_PREHEAT_BREW;
 
                        break;
 
                    case 1:
 
                        state = STATE_SETP;
 
                        break;
 
                    case 0:
 
                        state = STATE_SETP;
 
                        break;
 
                    default:
 
                        state = STATE_PREHEAT_BREW;
 
                }
 
            }
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