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| author | Kevin O'Connor <kevin@koconnor.net> | 2016-06-05 10:29:09 -0400 |
|---|---|---|
| committer | Kevin O'Connor <kevin@koconnor.net> | 2016-06-05 10:52:46 -0400 |
| commit | 91e7807af61ba8a907f7eca8952efcb91ec81935 (patch) | |
| tree | f0349889493f09aacf5f427aee0550844d68ea85 /src | |
| parent | 38f1d78e1b3d4b196836d14c3eeef26c603642b2 (diff) | |
| download | kutter-91e7807af61ba8a907f7eca8952efcb91ec81935.tar.gz kutter-91e7807af61ba8a907f7eca8952efcb91ec81935.tar.xz kutter-91e7807af61ba8a907f7eca8952efcb91ec81935.zip | |
avr: Add config option to clear the CPU prescaler
Some AVR chips ship with a 1/8th clock divisor set. Add a compile
time option to manually clear this field at startup.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Diffstat (limited to 'src')
| -rw-r--r-- | src/avr/Kconfig | 14 | ||||
| -rw-r--r-- | src/avr/timer.c | 9 |
2 files changed, 23 insertions, 0 deletions
diff --git a/src/avr/Kconfig b/src/avr/Kconfig index 5056e86a..24e33812 100644 --- a/src/avr/Kconfig +++ b/src/avr/Kconfig @@ -44,6 +44,20 @@ config CLOCK_FREQ default 16000000 if AVR_FREQ_16000000 default 20000000 if AVR_FREQ_20000000 +config CLEAR_PRESCALER + bool "Manually clear the CPU prescaler field at startup" + default n + help + Some AVR chips ship with a "clock prescaler" that causes the + chip to run at 1/8th speed. Enable this setting to clear the + prescaler field at startup which will cause the chip to run + without a clock divisor. + +config AVR_CLKPR + int + default 0 if CLEAR_PRESCALER + default -1 + config AVR_STACK_SIZE int default 256 if MACH_atmega2560 diff --git a/src/avr/timer.c b/src/avr/timer.c index 538f0b19..31f94caf 100644 --- a/src/avr/timer.c +++ b/src/avr/timer.c @@ -5,6 +5,7 @@ // This file may be distributed under the terms of the GNU GPLv3 license. #include <avr/interrupt.h> // TCNT1 +#include "autoconf.h" // CONFIG_AVR_CLKPR #include "command.h" // shutdown #include "irq.h" // irq_save #include "sched.h" // sched_timer_kick @@ -49,6 +50,14 @@ ISR(TIMER1_COMPA_vect) static void timer_init(void) { + if (CONFIG_AVR_CLKPR != -1 && (uint8_t)CONFIG_AVR_CLKPR != CLKPR) { + // Program the clock prescaler + uint8_t flag = irq_save(); + CLKPR = 0x80; + CLKPR = CONFIG_AVR_CLKPR; + irq_restore(flag); + } + // no outputs TCCR1A = 0; // Normal Mode |