altos/micropeak: Clock micropeak at 250kHz to save power

This reduces average current consumption from 2mA to .4mA. This
makes the battery last longer, but also gets the current under
something that the typical CR1025 battery can support. Would be nice
to reduce current even further; cheap CR1025 batteries still seem to
fade a bit at this current level.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/src/attiny/ao_clock.c b/src/attiny/ao_clock.c
index a381b47f71ea233e20f651cb865dc9cea0bb5f44..b40f59d4cc36711ce8744cd1632b14440ee23c25 100644 (file)
--- a/src/attiny/ao_clock.c
+++ b/src/attiny/ao_clock.c
@@ -39,12 +39,45 @@ ao_time(void)
        return r;
 }
 
        return r;
 }
 

+#if AVR_CLOCK == 8000000UL
+#define AO_CLKPS       0       /* divide by 1 */
+#define AO_CS          10      /* prescale by 512 */
+#endif
+#if AVR_CLOCK == 4000000UL
+#define AO_CLKPS       1       /* divide by 2 */
+#define AO_CS          9       /* prescale by 256 */
+#endif
+#if AVR_CLOCK == 2000000UL
+#define AO_CLKPS       2       /* divide by 4 */
+#define AO_CS          8       /* prescale by 128 */
+#endif
+#if AVR_CLOCK == 1000000UL
+#define AO_CLKPS       3       /* divide by 8 */
+#define AO_CS          7       /* prescale by 64 */
+#endif
+#if AVR_CLOCK == 500000UL
+#define AO_CLKPS       4       /* divide by 16 */
+#define AO_CS          6       /* prescale by 32 */
+#endif
+#if AVR_CLOCK == 250000UL
+#define AO_CLKPS       5       /* divide by 32 */
+#define AO_CS          5       /* prescale by 16 */
+#endif
+#if AVR_CLOCK == 125000UL
+#define AO_CLKPS       6       /* divide by 64 */
+#define AO_CS          4       /* prescale by 32 */
+#endif
+#if AVR_CLOCK == 62500UL
+#define AO_CLKPS       7       /* divide by 128 */
+#define AO_CS          4       /* prescale by 32 */
+#endif
+

 void
 ao_timer_init(void)
 {
        cli();
        CLKPR = (1 << CLKPCE);
 void
 ao_timer_init(void)
 {
        cli();
        CLKPR = (1 << CLKPCE);

-       CLKPR = 0;
+       CLKPR = (AO_CLKPS << CLKPS0);

        sei();
 
        /* Overall division ratio is 512 * 125,
        sei();
 
        /* Overall division ratio is 512 * 125,


@@ -55,10 +88,7 @@ ao_timer_init(void)
                 (0 << PWM1A) |         /* Not PWM mode */
                 (0 << COM1A0) |        /* Don't change output pins */
                 (0 << COM1A1) |        /*  ... */
                 (0 << PWM1A) |         /* Not PWM mode */
                 (0 << COM1A0) |        /* Don't change output pins */
                 (0 << COM1A1) |        /*  ... */

-                (1 << CS13) |          /* Prescale by 512 */
-                (0 << CS12) |          /*  ... */
-                (1 << CS11) |          /*  ... */
-                (0 << CS10));          /*  ... */
+                (AO_CS << CS10));      /* Prescale */

        GTCCR = ((0 << PWM1B) |         /* Not PWM mode */
                 (0 << COM1B1) |        /* Don't change output pins */
                 (0 << COM1B0) |        /*  ... */
        GTCCR = ((0 << PWM1B) |         /* Not PWM mode */
                 (0 << COM1B1) |        /* Don't change output pins */
                 (0 << COM1B0) |        /*  ... */

diff --git a/src/micropeak/ao_pins.h b/src/micropeak/ao_pins.h
index 67de1a8e8667cfd09fe355dfaced85908b592c97..cf5951df5b90f42f0dbb598900728089a8c54693 100644 (file)
--- a/src/micropeak/ao_pins.h
+++ b/src/micropeak/ao_pins.h
@@ -32,7 +32,7 @@
 #define HAS_MS5611             0
 #define HAS_EEPROM             0
 #define HAS_BEEP               0
 #define HAS_MS5611             0
 #define HAS_EEPROM             0
 #define HAS_BEEP               0

-#define AVR_CLOCK              8000000UL
+#define AVR_CLOCK              250000UL

 
 /* SPI */
 #define SPI_PORT               PORTB
 
 /* SPI */
 #define SPI_PORT               PORTB