switched to fast PWM, added workaround for UART transmission errors

schaltungen/displayboard_servo/software/src/main.c

@@ -14,13 +14,17 @@
 
 #define BUFSIZE     10
 
+/* ugly workaround for massive out of sequence power values,
+ * USART code seems to forget characters from time to time */
+#define MAX_ALLOWED_DEVIATION 50
+#define MAX_FAILS 3
+
 #define DEBUG2
 
 volatile uint16_t syscounter = 0;
-volatile uint16_t power;
 uint8_t data_count = 0;
 char data_in[BUFSIZE];
-
+volatile uint16_t current_pulse_width = 250;
 
 void reset_input_buffer(void) {
     data_count = 0;
@@ -28,11 +32,14 @@ void reset_input_buffer(void) {
 }
 
 static void timer_init(void) {
-	// CTC Mode for Timer 1 (16Bit) with prescale of 64
+    // set Timer 1 to fast PWM mode, with prescale of 64, clear OC1A as soon as
-	TCCR1B |= _BV(WGM12) | _BV(CS11) | _BV(CS10);       
+    // TCNT1 reaches OCR1A, set OC1A as soon as it reaches ICR1
-	OCR1A = 2250;           // set Servo to max. position
+    // NOTE: one tick is equivalent to 8 usecs
-	TIMSK |= _BV(OCIE1A);	// enable timer interrupt
+    TCCR1A = _BV(COM1A1) | _BV(WGM11); 
-	TCCR1A |= _BV(COM1A0);   // toggle OCR1A on overflow
+    TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS11) | _BV(CS10);
+    ICR1  = 2500;        // period of 20 msecs
+    OCR1A = 250;         // inital pulse width of 2 msecs (10% duty cycle)
+    TIMSK |= _BV(TOIE1); // enable overflow interrupt
 
     // CTC Mode for Timer 0 (8Bit) with prescale of 1024
     TCCR0B |= _BV(CS02) | _BV(CS00); // prescaler
@@ -47,6 +54,9 @@ static void ports_init(void) {
 }
 
 static void work_uart() {
+    static uint16_t power;
+    static uint8_t fail_counter = 0;
+    uint16_t new_power = 0, diff = 0;
     uint16_t c = uart_getc();
 
     if ( !(c & UART_NO_DATA) ) {
@@ -70,19 +80,28 @@ static void work_uart() {
 #endif
 
         if (cur == 13 || cur == '\n') {
+            new_power = atoi(data_in);
+            new_power = new_power <= POWER_MAX ? new_power : POWER_MAX;
+            diff = new_power > power ? new_power - power : power - new_power;
 
-            power = atol(data_in);
+            if(diff < MAX_ALLOWED_DEVIATION || fail_counter > MAX_FAILS) {
-            if(power > POWER_MAX) power = POWER_MAX;
+#ifdef UART_DEBUG
-
+                uart_puts_P("Transmitted power = ");
-#ifdef DEBUG
-            uart_puts_P("power = ");
                 uart_print_uint16(power);
                 uart_puts_P("\r\n");
 #endif
-            if(power > 0) {
+                power = new_power;
+                fail_counter = 0;
                 set_servo(power);
             }
-           
+            else {
+#ifdef UART_DEBUG
+                uart_puts_P("Oooooooops!!! Transmitted power = ");
+                uart_print_uint16(new_power);
+                uart_puts_P("\r\n");
+#endif
+                fail_counter++;
+            }
             reset_input_buffer();
         }
     }
@@ -94,15 +113,10 @@ static void work_uart() {
  *  \param  display     The power value from 0 to 400 (including bounds)
  */
 void set_servo(uint16_t display) {
-	int diff;
+    // invert value and ensure that we don't exceed the limit
-
+    display = POWER_MAX - (display < POWER_MAX ? display : POWER_MAX);
-	if( display > POWER_MAX ) display = POWER_MAX;
+    // *10 otherwise we need float
-
+    display = (display * 10u) / ((POWER_MAX * 10u) / SERVO_STEPS) + SERVO_STEPS;
-	display = POWER_MAX-display;        // invert the value / servo
-
-	display = display * 10;				// *10 otherwise we need float
-	display = display / ((POWER_MAX * 10) / SERVO_STEPS);
-	display = display + SERVO_STEPS;
 
 #ifdef DEBUG
     uart_puts_P("display = ");
@@ -110,37 +124,11 @@ void set_servo(uint16_t display) {
     uart_puts_P("\r\n");
 #endif
 
-    if( display < 125 ) display = 125;	// just make sure, the timer
+    cli();
-	if( display > 250 ) display = 250;  // is never out ouf 20ms grid
+    current_pulse_width = display;
-
+    sei();
-    
-    // check if timer is currently in the small pulse, then sleep here 2ms
-    // and do again
-    
-    
-    if(OCR1A <= 2250) {
-        _delay_ms(10);
 }
 
-	//cli();								// read and write atomic
-	TIMSK &= ~(_BV(OCIE1A));
-	diff = OCR1A - (2500-display);
-    if(diff <=20 && diff >= -20) {
-    	OCR1A = 2500-display;
-	}
-	else {
-		if(diff <=20) {
-			OCR1A = OCR1A+5;
-		}
-		else if ( diff >= -20 ) {
-			OCR1A = OCR1A-5;
-		}
-	}	
-    //sei();
-    TIMSK |= _BV(OCIE1A);
-}
-
-
 /**
  * \brief   the method moves the servo one complete cycle
  */
@@ -153,17 +141,16 @@ static void demo_display(void) {
     wait(100);
 }
 
-
 int main(void) {
-	
     sei();
+
     ports_init();
     timer_init();
     uart_init(UART_BAUD_SELECT(38400,F_CPU));
+
     reset_input_buffer();
     // demo_display();
 
-	
     while(1) {
         work_uart();
 
@@ -183,14 +170,8 @@ int main(void) {
     return(0);
 }
 
-/**
+ISR(TIMER1_OVF_vect) {
- * \brief	this is our timer for PWM generation and system clock
+    OCR1A = current_pulse_width;
- * 			the system clock varies a bit, but this does not matter
- */
-ISR(TIMER1_COMPA_vect) {
-	OCR1A = 2500-OCR1A;	// Das Servosignal wird aus der Differenz von
-						// Periodenlänge (2500*0,008ms=20ms) und letztem
-						// Vergleichswert (OCR1A) gebildet	
 }
 
 ISR(TIMER0_COMPA_vect) {

schaltungen/displayboard_servo/tester.py

@@ -13,7 +13,7 @@ while 1:
 	tdata = ser.read()
 
 	if tdata == 'a':
-		print power
+		print 'Local power = ' + str(power)
 		ser.write(str(power) + '\x0d')
 		#ser.write('100\n')
 		ser.flush()
@@ -30,7 +30,9 @@ while 1:
 		if power < 0:
 			power = 0
 			incdec = 0
-	#else:
+	else:
+		sys.stdout.write(tdata)
+		sys.stdout.write(ser.readline())
 		#data_left = ser.inWaiting()
 		#tdata += ser.read(data_left)
 		#print tdata