It simplifies the virtual "count up timer" and improves
the accuracy a little. The LDVAL for the prescaler should
be set as a number of prescaler cycles-1. The virtual
up-counter should be corrected in the isr by +1
(See PIT reference manual). This also fixes a bug where
the timer is not used by xtimer and up-counter does not overflow.
Reading CVAL after stopping timer seem to return zero.
Ref. manual states: "The counter period can be restarted, by first
disabling, and then enabling the timer with TCTRLn[TEN]", but does not
state whether the reset of CVAL happens on TEN 0->1 transition, or 1->0
transtion. Empirical evidence suggests the latter is the implemented behaviour.
add peripheral drivers for Freescale Kinetis MCUs:
adc driver
cpuid driver
gpio driver
hwtimer_arch driver (hwtimer used Low Power Timer)
i2c driver (master mode only)
mcg driver
pwm driver
random_rnga driver
random_rngb driver
rtc driver
spi driver
timer driver (timer used Periodic Interrupt Timer)
uart driver
add doc.txt (configuration examples)
random_rnga: Update RNGA driver in preparation for RNGB driver.
random_rngb: Add RNGB driver.
spi: refactor SPI to work for multiple CTARS, add spi_acquire, spi_release
gpio: Add gpio_irq_enable, gpio_irq_disable. Refactor GPIO.
gpio: Add gpio_irq_enable, gpio_irq_disable.
gpio: Refactor ISR functions to work with all GPIOs (0-31) and all ports (PORTA-PORTH)
adc: Refactor ADC, add calibration and scaling.
Added integer scaling of results in adc_map.
Handle precision setting in adc_init.
Set ADC clock divider depending on module clock.
Add ADC_1 as a possible device.
Add ADC calibration procedure according to K60 ref manual.
Handle ADC pins which are not part of the pin function mux.
Signed-off-by: Joakim Gebart <joakim.gebart@eistec.se>
