From 371da0c909098092db7b596496df9d58eed43703 Mon Sep 17 00:00:00 2001
From: Keith Packard <keithp@keithp.com>
Date: Tue, 30 Oct 2012 19:41:08 -0700
Subject: 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>
---
 src/attiny/ao_clock.c | 40 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 5 deletions(-)

(limited to 'src/attiny/ao_clock.c')

diff --git a/src/attiny/ao_clock.c b/src/attiny/ao_clock.c
index a381b47f..b40f59d4 100644
--- a/src/attiny/ao_clock.c
+++ b/src/attiny/ao_clock.c
@@ -39,12 +39,45 @@ ao_time(void)
 	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);
-	CLKPR = 0;
+	CLKPR = (AO_CLKPS << CLKPS0);
 	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) |	/*  ... */
-		 (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) |	/*  ... */
-- 
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