add a 0x00 command that means "I have nothing to say"

[protos/rc_servos.git] / main.c

diff --git a/main.c b/main.c
index 3509874..9c368d5 100644 (file)
--- a/main.c
+++ b/main.c
@@ -39,6 +39,10 @@ static volatile uint8_t done;
 static uint8_t portval;
 static uint8_t rxidx;
 
+static uint8_t icp_idx = NB_SERVO;
+static uint16_t icp_servos[NB_SERVO];
+static uint16_t icp_prev;
+
 #define BYPASS_ENABLE 14
 #define BYPASS_DISABLE 15
 
@@ -48,11 +52,13 @@ static uint8_t rxidx;
 /*
  * SPI protocol:
  *
- * A command is stored on 2 bytes. The first one has its msb to 0, and the
- * second one to 1. The first received byte contains the command number, and the
- * msb of the servo value. The second byte contains the lsb of the servo value.
+ * A command is stored on 2 bytes (except command 0). The first byte
+ * has its most significant bit to 0, and the second one to 1. The
+ * first received byte contains the command number, and the msb of the
+ * servo value. The second byte contains the lsb of the servo value.
  *
- * Commands 0 to NB_SERVO are to set the value of servo.
+ * Command 0 is only one byte long, it means "I have nothing to say".
+ * Commands 1 to NB_SERVO+1 are to set the value of servo.
  * Command 14 is to enable bypass mode.
  * Command 15 is to disable bypass mode.
  */
@@ -102,6 +108,10 @@ static void poll_spi(void)
 
        if (rxidx == 0) {
                byte0.u8 = c;
+
+               /* command num 0 is ignored */
+               if (byte0.cmd_num == 0)
+                       return;
        }
        else {
                uint16_t val;
@@ -110,10 +120,10 @@ static void poll_spi(void)
 
                /* process command */
 
-               if (byte0.cmd_num < NB_SERVO) {
+               if (byte0.cmd_num < NB_SERVO+1) {
                        val = (uint16_t)byte0.val_msb << 7;
                        val += byte1.val_lsb;
-                       servo_table[byte0.cmd_num].command = val;
+                       servo_table[byte0.cmd_num-1].command = val;
                }
                else if (byte0.cmd_num == BYPASS_ENABLE) {
                        bypass = 1;
@@ -126,6 +136,53 @@ static void poll_spi(void)
        rxidx ^= 1;
 }
 
+static void poll_input_capture(void)
+{
+       uint16_t icp, diff;
+       uint8_t rising;
+
+       /* no new sample, return */
+       if ((TIFR1 & _BV(ICF1)) == 0)
+               return;
+
+       sei();
+       icp = ICR1;
+       cli();
+
+       rising = TCCR1B & _BV(ICES1);
+
+       /* change the edge type */
+       TCCR1B ^= _BV(ICES1);
+
+       /* clear the flag */
+       TIFR1 = TIFR1 | _BV(ICF1);
+
+       diff = icp - icp_prev;
+       icp_prev = icp;
+
+       /* a rising edge with at least 2ms of state 0 means that we
+        * get the first servo */
+       if (rising == 1 && diff > 2000) {
+               icp_idx = 0;
+               return;
+       }
+
+       /* get the value for the servo */
+       if (rising == 0 && icp_idx < NB_SERVO) {
+               if (diff < 1000)
+                       icp_servos[icp_idx] = 0;
+               else
+                       icp_servos[icp_idx] = diff - 1000;
+               icp_idx++;
+       }
+}
+
+static void poll(void)
+{
+       poll_spi();
+       poll_input_capture();
+}
+
 static void load_timer_at(uint16_t t)
 {
        OCR1A = t;
@@ -143,7 +200,7 @@ static void do_one_servo(struct servo *s)
        t = TCNT1;
        load_timer_at(t + 20);
        while (done == 0)
-               poll_spi();
+               poll();
 
        /* reset bit */
        done = 0;
@@ -151,7 +208,7 @@ static void do_one_servo(struct servo *s)
        //portval = PORTC & (~(1 << s->bit));
        load_timer_at(t + 20 + 1000 + s->command);
        while (done == 0)
-               poll_spi();
+               poll();
 }
 
 int main(void)
@@ -178,9 +235,10 @@ int main(void)
        /* servo outputs PD2-PD7 */
        DDRD = 0xfc;
 
-       /* start timer1 at clk/8 (1Mhz) */
+       /* start timer1 at clk/8 (1Mhz), enable noise canceler on
+        * input capture, capture rising edge */
        TCNT1 = 0;
-       TCCR1B = _BV(CS11);
+       TCCR1B = _BV(CS11) | _BV(ICNC1) | _BV(ICES1);
 
        /* start timer0 at clk/1024 (~8Khz) */
        TCNT0 = 0;
@@ -202,7 +260,7 @@ int main(void)
                        diff = TCNT0 - t;
                        if (diff >= 160)
                                break;
-                       poll_spi();
+                       poll();
                }
                /* bypass mode */
                if (bypass == 1) {
@@ -213,7 +271,7 @@ int main(void)
                                tmp &= 0x3f;
                                tmp <<= 2;
                                PORTD = tmp;
-                               poll_spi();
+                               poll();
                        }
                        LED_OFF();
                }