rc_balance.c

/**
* @example rc_balance
*
* Reference solution for balancing EduMiP
**/
 
#include <stdio.h>
#include <unistd.h> // for isatty()
#include <stdlib.h> // for strtof()
#include <math.h> // for M_PI
#include <robotcontrol.h>
 
#include "rc_balance_defs.h"
 
/**
 * NOVICE: Drive rate and turn rate are limited to make driving easier.
 * ADVANCED: Faster drive and turn rate for more fun.
 */
typedef enum drive_mode_t{
        NOVICE,
        ADVANCED
}drive_mode_t;
 
/**
 * ARMED or DISARMED to indicate if the controller is running
 */
typedef enum arm_state_t{
        ARMED,
        DISARMED
}arm_state_t;
 
/**
 * Feedback controller setpoint written to by setpoint_manager and read by the
 * controller.
 */
typedef struct setpoint_t{
        arm_state_t arm_state;  ///< see arm_state_t declaration
        drive_mode_t drive_mode;///< NOVICE or ADVANCED
        double theta;           ///< body lean angle (rad)
        double phi;             ///< wheel position (rad)
        double phi_dot;         ///< rate at which phi reference updates (rad/s)
        double gamma;           ///< body turn angle (rad)
        double gamma_dot;       ///< rate at which gamma setpoint updates (rad/s)
}setpoint_t;
 
/**
 * This is the system state written to by the balance controller.
 */
typedef struct core_state_t{
        double wheelAngleR;     ///< wheel rotation relative to body
        double wheelAngleL;
        double theta;           ///< body angle radians
        double phi;             ///< average wheel angle in global frame
        double gamma;           ///< body turn (yaw) angle radians
        double vBatt;           ///< battery voltage
        double d1_u;            ///< output of balance controller D1 to motors
        double d2_u;            ///< output of position controller D2 (theta_ref)
        double d3_u;            ///< output of steering controller D3 to motors
        double mot_drive;       ///< u compensated for battery voltage
} core_state_t;
 
// possible modes, user selected with command line arguments
typedef enum m_input_mode_t{
        NONE,
        DSM,
        STDIN
} m_input_mode_t;
 
 
static void __print_usage(void);
static void __balance_controller(void);         ///< mpu interrupt routine
static void* __setpoint_manager(void* ptr);     ///< background thread
static void* __battery_checker(void* ptr);      ///< background thread
static void* __printf_loop(void* ptr);          ///< background thread
static int __zero_out_controller(void);
static int __disarm_controller(void);
static int __arm_controller(void);
static int __wait_for_starting_condition(void);
static void __on_pause_press(void);
static void __on_mode_release(void);
 
 
// global variables
// Must be declared static so they get zero initalized
static core_state_t cstate;
static setpoint_t setpoint;
static rc_filter_t D1 = RC_FILTER_INITIALIZER;
static rc_filter_t D2 = RC_FILTER_INITIALIZER;
static rc_filter_t D3 = RC_FILTER_INITIALIZER;
static rc_mpu_data_t mpu_data;
static m_input_mode_t m_input_mode = DSM;
 
/*
 * printed if some invalid argument was given
 */
static void __print_usage(void)
{
        printf("\n");
        printf("-i {dsm|stdin|none}     specify input\n");
        printf("-q                      Don't print diagnostic info\n");
        printf("-h                      print this help message\n");
        printf("\n");
}
 
/**
 * Initialize the filters, mpu, threads, & wait until shut down
 *
 * @return     0 on success, -1 on failure
 */
int main(int argc, char *argv[])
{
        int c;
        pthread_t setpoint_thread = 0;
        pthread_t battery_thread = 0;
        pthread_t printf_thread = 0;
        bool adc_ok = true;
        bool quiet = false;
 
        // parse arguments
        opterr = 0;
        while ((c = getopt(argc, argv, "i:qh")) != -1){
                switch (c){
                case 'i': // input option
                        if(!strcmp("dsm", optarg)) {
                                m_input_mode = DSM;
                        } else if(!strcmp("stdin", optarg)) {
                                m_input_mode = STDIN;
                        } else if(!strcmp("none", optarg)){
                                m_input_mode = NONE;
                        } else {
                                __print_usage();
                                return -1;
                        }
                        break;
                case 'q':
                        quiet = true;
                        break;
                case 'h':
                        __print_usage();
                        return -1;
                        break;
                default:
                        __print_usage();
                        return -1;
                        break;
                }
        }
 
        // make sure another instance isn't running
        // if return value is -3 then a background process is running with
        // higher privaledges and we couldn't kill it, in which case we should
        // not continue or there may be hardware conflicts. If it returned -4
        // then there was an invalid argument that needs to be fixed.
        if(rc_kill_existing_process(2.0)<-2) return -1;
 
        // start signal handler so we can exit cleanly
        if(rc_enable_signal_handler()==-1){
                fprintf(stderr,"ERROR: failed to start signal handler\n");
                return -1;
        }
 
        // initialize buttons
        if(rc_button_init(RC_BTN_PIN_PAUSE, RC_BTN_POLARITY_NORM_HIGH,
                                                RC_BTN_DEBOUNCE_DEFAULT_US)){
                fprintf(stderr,"ERROR: failed to initialize pause button\n");
                return -1;
        }
        if(rc_button_init(RC_BTN_PIN_MODE, RC_BTN_POLARITY_NORM_HIGH,
                                                RC_BTN_DEBOUNCE_DEFAULT_US)){
                fprintf(stderr,"ERROR: failed to initialize mode button\n");
                return -1;
        }
 
        // Assign functions to be called when button events occur
        rc_button_set_callbacks(RC_BTN_PIN_PAUSE,__on_pause_press,NULL);
        rc_button_set_callbacks(RC_BTN_PIN_MODE,NULL,__on_mode_release);
 
        // initialize enocders
        if(rc_encoder_eqep_init()==-1){
                fprintf(stderr,"ERROR: failed to initialize eqep encoders\n");
                return -1;
        }
 
        // initialize motors
        if(rc_motor_init()==-1){
                fprintf(stderr,"ERROR: failed to initialize motors\n");
                return -1;
        }
        rc_motor_standby(1); // start with motors in standby
 
        // start dsm listener
        if(m_input_mode == DSM){
                if(rc_dsm_init()==-1){
                        fprintf(stderr,"failed to start initialize DSM\n");
                        return -1;
                }
        }
 
        // initialize adc
        if(rc_adc_init()==-1){
                fprintf(stderr, "failed to initialize adc\n");
                adc_ok = false;
        }
 
        // make PID file to indicate your project is running
        // due to the check made on the call to rc_kill_existing_process() above
        // we can be fairly confident there is no PID file already and we can
        // make our own safely.
        rc_make_pid_file();
 
        printf("\nPress and release MODE button to toggle DSM drive mode\n");
        printf("Press and release PAUSE button to pause/start the motors\n");
        printf("hold pause button down for 2 seconds to exit\n");
 
        if(rc_led_set(RC_LED_GREEN, 0)==-1){
                fprintf(stderr, "ERROR in rc_balance, failed to set RC_LED_GREEN\n");
                return -1;
        }
        if(rc_led_set(RC_LED_RED, 1)==-1){
                fprintf(stderr, "ERROR in rc_balance, failed to set RC_LED_RED\n");
                return -1;
        }
 
        // set up mpu configuration
        rc_mpu_config_t mpu_config = rc_mpu_default_config();
        mpu_config.dmp_sample_rate = SAMPLE_RATE_HZ;
        mpu_config.orient = ORIENTATION_Y_UP;
 
        // if gyro isn't calibrated, run the calibration routine
        if(!rc_mpu_is_gyro_calibrated()){
                printf("Gyro not calibrated, automatically starting calibration routine\n");
                printf("Let your MiP sit still on a firm surface\n");
                rc_mpu_calibrate_gyro_routine(mpu_config);
        }
 
        // make sure setpoint starts at normal values
        setpoint.arm_state = DISARMED;
        setpoint.drive_mode = NOVICE;
 
        // set up D1 Theta controller
        double D1_num[] = D1_NUM;
        double D1_den[] = D1_DEN;
        if(rc_filter_alloc_from_arrays(&D1, DT, D1_num, D1_NUM_LEN, D1_den, D1_DEN_LEN)){
                fprintf(stderr,"ERROR in rc_balance, failed to make filter D1\n");
                return -1;
        }
        D1.gain = D1_GAIN;
        rc_filter_enable_saturation(&D1, -1.0, 1.0);
        rc_filter_enable_soft_start(&D1, SOFT_START_SEC);
 
        // set up D2 Phi controller
        double D2_num[] = D2_NUM;
        double D2_den[] = D2_DEN;
        if(rc_filter_alloc_from_arrays(&D2, DT, D2_num, D2_NUM_LEN, D2_den, D2_DEN_LEN)){
                fprintf(stderr,"ERROR in rc_balance, failed to make filter D2\n");
                return -1;
        }
        D2.gain = D2_GAIN;
        rc_filter_enable_saturation(&D2, -THETA_REF_MAX, THETA_REF_MAX);
        rc_filter_enable_soft_start(&D2, SOFT_START_SEC);
 
        printf("Inner Loop controller D1:\n");
        rc_filter_print(D1);
        printf("\nOuter Loop controller D2:\n");
        rc_filter_print(D2);
 
        // set up D3 gamma (steering) controller
        if(rc_filter_pid(&D3, D3_KP, D3_KI, D3_KD, 4*DT, DT)){
                fprintf(stderr,"ERROR in rc_balance, failed to make steering controller\n");
                return -1;
        }
        rc_filter_enable_saturation(&D3, -STEERING_INPUT_MAX, STEERING_INPUT_MAX);
 
        // start a thread to slowly sample battery
        if (adc_ok) {
                if(rc_pthread_create(&battery_thread, __battery_checker, (void*) NULL, SCHED_OTHER, 0)){
                        fprintf(stderr, "failed to start battery thread\n");
                        return -1;
                }
        }
        else { // If we can't get the battery voltage
                cstate.vBatt = V_NOMINAL; // Set to a nominal value
        }
 
        // wait for the battery thread to make the first read
        while(cstate.vBatt<1.0 && rc_get_state()!=EXITING) rc_usleep(10000);
 
        // start printf_thread if running from a terminal
        // if it was started as a background process then don't bother
        if(isatty(fileno(stdout)) && (quiet == false)){
                if(rc_pthread_create(&printf_thread, __printf_loop, (void*) NULL, SCHED_OTHER, 0)){
                        fprintf(stderr, "failed to start printf thread\n");
                        return -1;
                }
        }
 
        // start mpu
        if(rc_mpu_initialize_dmp(&mpu_data, mpu_config)){
                fprintf(stderr,"ERROR: can't talk to IMU, all hope is lost\n");
                rc_led_blink(RC_LED_RED, 5, 5);
                return -1;
        }
 
        // start balance stack to control setpoints
        if(rc_pthread_create(&setpoint_thread, __setpoint_manager, (void*) NULL, SCHED_OTHER, 0)){
                fprintf(stderr, "failed to start setpoint thread\n");
                return -1;
        }
 
        // this should be the last step in initialization
        // to make sure other setup functions don't interfere
        rc_mpu_set_dmp_callback(&__balance_controller);
 
        // start in the RUNNING state, pressing the pause button will swap to
        // the PAUSED state then back again.
        printf("\nHold your MIP upright to begin balancing\n");
        rc_set_state(RUNNING);
 
        // chill until something exits the program
        rc_set_state(RUNNING);
        while(rc_get_state()!=EXITING){
                rc_usleep(200000);
        }
 
        // join threads
        rc_pthread_timed_join(setpoint_thread, NULL, 1.5);
        if (battery_thread) rc_pthread_timed_join(battery_thread, NULL, 1.5);
        if (printf_thread) rc_pthread_timed_join(printf_thread, NULL, 1.5);
 
        // cleanup
        rc_filter_free(&D1);
        rc_filter_free(&D2);
        rc_filter_free(&D3);
        rc_mpu_power_off();
        rc_led_set(RC_LED_GREEN, 0);
        rc_led_set(RC_LED_RED, 0);
        rc_led_cleanup();
        rc_encoder_eqep_cleanup();
        rc_button_cleanup();    // stop button handlers
        rc_remove_pid_file();   // remove pid file LAST
        return 0;
}
 
/**
 * This thread is in charge of adjusting the controller setpoint based on user
 * inputs from dsm radio control. Also detects pickup to control arming the
 * controller.
 *
 * @param      ptr   The pointer
 *
 * @return     { description_of_the_return_value }
 */
void* __setpoint_manager(__attribute__ ((unused)) void* ptr)
{
        double drive_stick, turn_stick; // input sticks
        int i, ch, chan, stdin_timeout = 0; // for stdin input
        char in_str[11];
 
        // wait for mpu to settle
        __disarm_controller();
        rc_usleep(2500000);
        rc_set_state(RUNNING);
        rc_led_set(RC_LED_RED,0);
        rc_led_set(RC_LED_GREEN,1);
 
        while(rc_get_state()!=EXITING){
                // clear out input of old data before waiting for new data
                if(m_input_mode == STDIN) fseek(stdin,0,SEEK_END);
 
                // sleep at beginning of loop so we can use the 'continue' statement
                rc_usleep(1000000/SETPOINT_MANAGER_HZ);
 
                // nothing to do if paused, go back to beginning of loop
                if(rc_get_state() != RUNNING || m_input_mode == NONE) continue;
 
                // if we got here the state is RUNNING, but controller is not
                // necessarily armed. If DISARMED, wait for the user to pick MIP up
                // which will we detected by wait_for_starting_condition()
                if(setpoint.arm_state == DISARMED){
                        if(__wait_for_starting_condition()==0){
                                __zero_out_controller();
                                __arm_controller();
                        }
                        else continue;
                }
 
                // if dsm is active, update the setpoint rates
                switch(m_input_mode){
                case NONE:
                        continue;
                case DSM:
                        if(rc_dsm_is_new_data()){
                                // Read normalized (+-1) inputs from RC radio stick and multiply by
                                // polarity setting so positive stick means positive setpoint
                                turn_stick  = rc_dsm_ch_normalized(DSM_TURN_CH) * DSM_TURN_POL;
                                drive_stick = rc_dsm_ch_normalized(DSM_DRIVE_CH)* DSM_DRIVE_POL;
 
                                // saturate the inputs to avoid possible erratic behavior
                                rc_saturate_double(&drive_stick,-1,1);
                                rc_saturate_double(&turn_stick,-1,1);
 
                                // use a small deadzone to prevent slow drifts in position
                                if(fabs(drive_stick)<DSM_DEAD_ZONE) drive_stick = 0.0;
                                if(fabs(turn_stick)<DSM_DEAD_ZONE)  turn_stick  = 0.0;
 
                                // translate normalized user input to real setpoint values
                                switch(setpoint.drive_mode){
                                case NOVICE:
                                        setpoint.phi_dot   = DRIVE_RATE_NOVICE * drive_stick;
                                        setpoint.gamma_dot =  TURN_RATE_NOVICE * turn_stick;
                                        break;
                                case ADVANCED:
                                        setpoint.phi_dot   = DRIVE_RATE_ADVANCED * drive_stick;
                                        setpoint.gamma_dot = TURN_RATE_ADVANCED  * turn_stick;
                                        break;
                                default: break;
                                }
                        }
                        // if dsm had timed out, put setpoint rates back to 0
                        else if(rc_dsm_is_connection_active()==0){
                                setpoint.theta = 0;
                                setpoint.phi_dot = 0;
                                setpoint.gamma_dot = 0;
                                continue;
                        }
                        break;
                case STDIN:
                        i = 0;
 
                        while ((ch = getchar()) != EOF && i < 10){
                                stdin_timeout = 0;
                                if(ch == 'n' || ch == '\n'){
                                        if(i > 2){
                                                in_str[i-2] = '\0'; // Null terminate string in case this command is shorter than last one
                                                if(chan == DSM_TURN_CH){
                                                        turn_stick = strtof(in_str, NULL) * DSM_TURN_POL;
                                                        setpoint.gamma_dot = turn_stick;
                                                }
                                                else if(chan == DSM_DRIVE_CH){
                                                        drive_stick = strtof(in_str, NULL) * DSM_DRIVE_POL;
                                                        setpoint.phi_dot = drive_stick;
                                                }
                                        }
                                        if(ch == 'n') i = 1;
                                        else i = 0;
                                }
                                else if(i == 1){
                                        chan = ch - 0x30;
                                        i = 2;
                                }
                                else{
                                        in_str[i-2] = ch;
                                        i++;
                                }
                        }
 
                        // if it has been more than 1 second since getting data
                        if(stdin_timeout >= SETPOINT_MANAGER_HZ){
                                setpoint.theta = 0;
                                setpoint.phi_dot = 0;
                                setpoint.gamma_dot = 0;
                        }
                        else{
                                stdin_timeout++;
                        }
                        continue;
                        break;
                default:
                        fprintf(stderr,"ERROR in setpoint manager, invalid input mode\n");
                        break;
                }
        }
 
        // if state becomes EXITING the above loop exists and we disarm here
        __disarm_controller();
        return NULL;
}
 
/**
 * discrete-time balance controller operated off mpu interrupt Called at
 * SAMPLE_RATE_HZ
 */
static void __balance_controller(void)
{
        static int inner_saturation_counter = 0;
        double dutyL, dutyR;
        /******************************************************************
        * STATE_ESTIMATION
        * read sensors and compute the state when either ARMED or DISARMED
        ******************************************************************/
        // angle theta is positive in the direction of forward tip around X axis
        cstate.theta = mpu_data.dmp_TaitBryan[TB_PITCH_X] + BOARD_MOUNT_ANGLE;
 
        // collect encoder positions, right wheel is reversed
        cstate.wheelAngleR = (rc_encoder_eqep_read(ENCODER_CHANNEL_R) * 2.0 * M_PI) \
                                /(ENCODER_POLARITY_R * GEARBOX * ENCODER_RES);
        cstate.wheelAngleL = (rc_encoder_eqep_read(ENCODER_CHANNEL_L) * 2.0 * M_PI) \
                                /(ENCODER_POLARITY_L * GEARBOX * ENCODER_RES);
 
        // Phi is average wheel rotation also add theta body angle to get absolute
        // wheel position in global frame since encoders are attached to the body
        cstate.phi = ((cstate.wheelAngleL+cstate.wheelAngleR)/2) + cstate.theta;
 
        // steering angle gamma estimate
        cstate.gamma = (cstate.wheelAngleR-cstate.wheelAngleL) \
                                        * (WHEEL_RADIUS_M/TRACK_WIDTH_M);
 
        /*************************************************************
        * check for various exit conditions AFTER state estimate
        ***************************************************************/
        if(rc_get_state()==EXITING){
                rc_motor_set(0,0.0);
                return;
        }
        // if controller is still ARMED while state is PAUSED, disarm it
        if(rc_get_state()!=RUNNING && setpoint.arm_state==ARMED){
                __disarm_controller();
                return;
        }
        // exit if the controller is disarmed
        if(setpoint.arm_state==DISARMED){
                return;
        }
 
        // check for a tipover
        if(fabs(cstate.theta) > TIP_ANGLE){
                __disarm_controller();
                printf("tip detected \n");
                return;
        }
 
        /************************************************************
        * OUTER LOOP PHI controller D2
        * Move the position setpoint based on phi_dot.
        * Input to the controller is phi error (setpoint-state).
        *************************************************************/
        if(ENABLE_POSITION_HOLD){
                if(fabs(setpoint.phi_dot) > 0.001) setpoint.phi += setpoint.phi_dot*DT;
                cstate.d2_u = rc_filter_march(&D2,setpoint.phi-cstate.phi);
                setpoint.theta = cstate.d2_u;
        }
        else setpoint.theta = 0.0;
 
        /************************************************************
        * INNER LOOP ANGLE Theta controller D1
        * Input to D1 is theta error (setpoint-state). Then scale the
        * output u to compensate for changing battery voltage.
        *************************************************************/
        D1.gain = D1_GAIN * V_NOMINAL/cstate.vBatt;
        cstate.d1_u = rc_filter_march(&D1,(setpoint.theta-cstate.theta));
 
        /*************************************************************
        * Check if the inner loop saturated. If it saturates for over
        * a second disarm the controller to prevent stalling motors.
        *************************************************************/
        if(fabs(cstate.d1_u)>0.95) inner_saturation_counter++;
        else inner_saturation_counter = 0;
        // if saturate for a second, disarm for safety
        if(inner_saturation_counter > (SAMPLE_RATE_HZ*D1_SATURATION_TIMEOUT)){
                printf("inner loop controller saturated\n");
                __disarm_controller();
                inner_saturation_counter = 0;
                return;
        }
 
        /**********************************************************
        * gama (steering) controller D3
        * move the setpoint gamma based on user input like phi
        ***********************************************************/
        if(fabs(setpoint.gamma_dot)>0.0001) setpoint.gamma += setpoint.gamma_dot * DT;
        cstate.d3_u = rc_filter_march(&D3,setpoint.gamma - cstate.gamma);
 
        /**********************************************************
        * Send signal to motors
        * add D1 balance control u and D3 steering control also
        * multiply by polarity to make sure direction is correct.
        ***********************************************************/
        dutyL = cstate.d1_u - cstate.d3_u;
        dutyR = cstate.d1_u + cstate.d3_u;
        rc_motor_set(MOTOR_CHANNEL_L, MOTOR_POLARITY_L * dutyL);
        rc_motor_set(MOTOR_CHANNEL_R, MOTOR_POLARITY_R * dutyR);
 
        return;
}
 
/**
 * Clear the controller's memory and zero out setpoints.
 *
 * @return     { description_of_the_return_value }
 */
static int __zero_out_controller(void)
{
        rc_filter_reset(&D1);
        rc_filter_reset(&D2);
        rc_filter_reset(&D3);
        setpoint.theta = 0.0;
        setpoint.phi   = 0.0;
        setpoint.gamma = 0.0;
        rc_motor_set(0,0.0);
        return 0;
}
 
/**
 * disable motors & set the setpoint.core_mode to DISARMED
 *
 * @return     { description_of_the_return_value }
 */
static int __disarm_controller(void)
{
        rc_motor_standby(1);
        rc_motor_free_spin(0);
        setpoint.arm_state = DISARMED;
        return 0;
}
 
/**
 * zero out the controller & encoders. Enable motors & arm the controller.
 *
 * @return     0 on success, -1 on failure
 */
static int __arm_controller(void)
{
        __zero_out_controller();
        rc_encoder_eqep_write(ENCODER_CHANNEL_L,0);
        rc_encoder_eqep_write(ENCODER_CHANNEL_R,0);
        // prefill_filter_inputs(&D1,cstate.theta);
        rc_motor_standby(0);
        setpoint.arm_state = ARMED;
        return 0;
}
 
/**
 * Wait for MiP to be held upright long enough to begin. Returns
 *
 * @return     0 if successful, -1 if the wait process was interrupted by pause
 *             button or shutdown signal.
 */
static int __wait_for_starting_condition(void)
{
        int checks = 0;
        const int check_hz = 20;        // check 20 times per second
        int checks_needed = round(START_DELAY*check_hz);
        int wait_us = 1000000/check_hz;
 
        // wait for MiP to be tipped back or forward first
        // exit if state becomes paused or exiting
        while(rc_get_state()==RUNNING){
                // if within range, start counting
                if(fabs(cstate.theta) > START_ANGLE) checks++;
                // fell out of range, restart counter
                else checks = 0;
                // waited long enough, return
                if(checks >= checks_needed) break;
                rc_usleep(wait_us);
        }
        // now wait for MiP to be upright
        checks = 0;
        // exit if state becomes paused or exiting
        while(rc_get_state()==RUNNING){
                // if within range, start counting
                if(fabs(cstate.theta) < START_ANGLE) checks++;
                // fell out of range, restart counter
                else checks = 0;
                // waited long enough, return
                if(checks >= checks_needed) return 0;
                rc_usleep(wait_us);
        }
        return -1;
}
 
/**
 * Slow loop checking battery voltage. Also changes the D1 saturation limit
 * since that is dependent on the battery voltage.
 *
 * @return     nothing, NULL poitner
 */
static void* __battery_checker(__attribute__ ((unused)) void* ptr)
{
        double new_v;
        while(rc_get_state()!=EXITING){
                new_v = rc_adc_batt();
                // if the value doesn't make sense, use nominal voltage
                if (new_v>9.0 || new_v<5.0) new_v = V_NOMINAL;
                cstate.vBatt = new_v;
                rc_usleep(1000000 / BATTERY_CHECK_HZ);
        }
        return NULL;
}
 
/**
 * prints diagnostics to console this only gets started if executing from
 * terminal
 *
 * @return     nothing, NULL pointer
 */
static void* __printf_loop(__attribute__ ((unused)) void* ptr)
{
        rc_state_t last_rc_state, new_rc_state; // keep track of last state
        last_rc_state = rc_get_state();
        while(rc_get_state()!=EXITING){
                new_rc_state = rc_get_state();
                // check if this is the first time since being paused
                if(new_rc_state==RUNNING && last_rc_state!=RUNNING){
                        printf("\nRUNNING: Hold upright to balance.\n");
                        printf("    θ    |");
                        printf("  θ_ref  |");
                        printf("    φ    |");
                        printf("  φ_ref  |");
                        printf("    γ    |");
                        printf("  D1_u   |");
                        printf("  D3_u   |");
                        printf("  vBatt  |");
                        printf("arm_state|");
                        printf("\n");
                }
                else if(new_rc_state==PAUSED && last_rc_state!=PAUSED){
                        printf("\nPAUSED: press pause again to start.\n");
                }
                last_rc_state = new_rc_state;
 
                // decide what to print or exit
                if(new_rc_state == RUNNING){
                        printf("\r");
                        printf("%7.3f  |", cstate.theta);
                        printf("%7.3f  |", setpoint.theta);
                        printf("%7.3f  |", cstate.phi);
                        printf("%7.3f  |", setpoint.phi);
                        printf("%7.3f  |", cstate.gamma);
                        printf("%7.3f  |", cstate.d1_u);
                        printf("%7.3f  |", cstate.d3_u);
                        printf("%7.3f  |", cstate.vBatt);
 
                        if(setpoint.arm_state == ARMED) printf("  ARMED  |");
                        else printf("DISARMED |");
                        fflush(stdout);
                }
                rc_usleep(1000000 / PRINTF_HZ);
        }
        return NULL;
}
 
/**
 * Disarm the controller and set system state to paused. If the user holds the
 * pause button for 2 seconds, exit cleanly
 */
static void __on_pause_press(void)
{
        int i=0;
        const int samples = 100;        // check for release 100 times in this period
        const int us_wait = 2000000; // 2 seconds
 
        switch(rc_get_state()){
        // pause if running
        case EXITING:
                return;
        case RUNNING:
                rc_set_state(PAUSED);
                __disarm_controller();
                rc_led_set(RC_LED_RED,1);
                rc_led_set(RC_LED_GREEN,0);
                break;
        case PAUSED:
                rc_set_state(RUNNING);
                __disarm_controller();
                rc_led_set(RC_LED_GREEN,1);
                rc_led_set(RC_LED_RED,0);
                break;
        default:
                break;
        }
 
        // now wait to see if the user want to shut down the program
        while(i<samples){
                rc_usleep(us_wait/samples);
                if(rc_button_get_state(RC_BTN_PIN_PAUSE)==RC_BTN_STATE_RELEASED){
                        return; //user let go before time-out
                }
                i++;
        }
        printf("long press detected, shutting down\n");
        //user held the button down long enough, blink and exit cleanly
        rc_led_blink(RC_LED_RED,5,2);
        rc_set_state(EXITING);
        return;
}
 
/**
 * toggle between position and angle modes if MiP is paused
 */
static void __on_mode_release(void)
{
        // toggle between position and angle modes
        if(setpoint.drive_mode == NOVICE){
                setpoint.drive_mode = ADVANCED;
                printf("using drive_mode = ADVANCED\n");
        }
        else {
                setpoint.drive_mode = NOVICE;
                printf("using drive_mode = NOVICE\n");
        }
 
        rc_led_blink(RC_LED_GREEN,5,1);
        return;
}