K20 general and timer adjustments #264
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Added the required gpio-irq enable/disable + fixed bus_frequency
Timer/Wait timer
The timer which creates interrupts is now also done using one of the PIT channels. Since also here no chaining is possible we still need to do some bits in software, but 32-bit without prescaling is still better than 16-bit with. Also some code was moved around and naming conventions changes, since no lptmr is used anymore, and calling both pit-timer would get confusing
Pretty much copy pasta of KLxx sleep code with only tiny change
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And added sleep code also. For whoever is interested, all with default setup, so if you actually want to use regular sleep you should start disabling peripherals first: |
bogdanm
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Apr 22, 2014
K20 general and timer adjustments
bridadan
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initial issue and PR github templates
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Some bugs squished and interrupt code added to be compatible with current mbed api.
The K20 cannot chain its PIT timers, so no option to get 1us tick rate for them. Solution for the 'timer' timer was to create an interrupt every 1us and use a software timer. Now it uses almost the complete 32-bit range of the timer, and only does the last few bits in software. Downside: Software and hardware timer need to stay synced. Upside, don't need an interrupt every 1us, timer not working in irq context, etc.
Also the 'ticker' timer is moved to a PIT channel. 32-bit with no prescaler is better than 16-bit with prescaler. Especially since the K20 is a core-M4, and has no problems with integer multiplications and divisions (contrary to M0s).