mbed library sources: Modified to operate FRDM-KL25Z at 48MHz from internal 32kHz oscillator (nothing else changed).
Fork of mbed-src by
The only file that changed is: mbed-src-FLL48/targets/cmsis/TARGET_Freescale/TARGET_KL25Z/system_MKL25Z4.h
Diff: targets/hal/TARGET_Freescale/TARGET_KL05Z/us_ticker.c
- Revision:
- 20:4263a77256ae
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/targets/hal/TARGET_Freescale/TARGET_KL05Z/us_ticker.c Tue Sep 10 15:14:19 2013 +0300 @@ -0,0 +1,134 @@ +/* mbed Microcontroller Library + * Copyright (c) 2006-2013 ARM Limited + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +#include <stddef.h> +#include "us_ticker_api.h" +#include "PeripheralNames.h" + +/* Prototypes */ +static void pit_init(void); +static void lptmr_init(void); +static void lptmr_isr(void); + +/* Global variables */ +static uint32_t us_ticker_inited = 0; +static uint32_t us_ticker_int_counter = 0; +static uint16_t us_ticker_int_remainder = 0; + + +void us_ticker_init(void) { + if (us_ticker_inited) { + return; + } + us_ticker_inited = 1; + + pit_init(); + lptmr_init(); +} + +static void pit_init(void) { + SIM->SCGC6 |= SIM_SCGC6_PIT_MASK; // Clock PIT + PIT->MCR = 0; // Enable PIT + + // Channel 1 + PIT->CHANNEL[1].LDVAL = 0xFFFFFFFF; + PIT->CHANNEL[1].TCTRL = PIT_TCTRL_CHN_MASK; // Chain to timer 0, disable Interrupts + PIT->CHANNEL[1].TCTRL |= PIT_TCTRL_TEN_MASK; // Start timer 1 + + // Use channel 0 as a prescaler for channel 1 + PIT->CHANNEL[0].LDVAL = 23; + PIT->CHANNEL[0].TCTRL = PIT_TCTRL_TEN_MASK; // Start timer 0, disable interrupts +} + +uint32_t us_ticker_read() { + if (!us_ticker_inited) { + us_ticker_init(); + } + + // The PIT is a countdown timer + return ~(PIT->CHANNEL[1].CVAL); +} + +static void lptmr_init(void) { + SIM->SCGC5 |= SIM_SCGC5_LPTMR_MASK; + + LPTMR0->CSR = 0; + + NVIC_SetVector(LPTimer_IRQn, (uint32_t)lptmr_isr); + NVIC_EnableIRQ(LPTimer_IRQn); + + // Clock at (1)MHz -> (1)tick/us + LPTMR0->PSR = LPTMR_PSR_PCS(0); // MCGIRCLK -> 2MHz / presc 2 = 1MHz +} + +void us_ticker_disable_interrupt(void) { + LPTMR0->CSR &= ~LPTMR_CSR_TIE_MASK; +} + +void us_ticker_clear_interrupt(void) { + // we've already cleared interrupt in lptmr_isr +} + +static void lptmr_set(unsigned short count) { + // Reset + LPTMR0->CSR = 0; + + // Set the compare register + LPTMR0->CMR = count; + + // Enable interrupt + LPTMR0->CSR |= LPTMR_CSR_TIE_MASK; + + // Start the timer + LPTMR0->CSR |= LPTMR_CSR_TEN_MASK; +} + +static void lptmr_isr(void) { + // write 1 to TCF to clear the LPT timer compare flag + LPTMR0->CSR |= LPTMR_CSR_TCF_MASK; + + if (us_ticker_int_counter > 0) { + lptmr_set(0xFFFF); + us_ticker_int_counter--; + } else { + if (us_ticker_int_remainder > 0) { + lptmr_set(us_ticker_int_remainder); + us_ticker_int_remainder = 0; + } else { + // This function is going to disable the interrupts if there are + // no other events in the queue + us_ticker_irq_handler(); + } + } +} + +void us_ticker_set_interrupt(uint32_t timestamp) { + int32_t delta = (int32_t)(timestamp - us_ticker_read()); + if (delta <= 0) { + // This event was in the past: + us_ticker_irq_handler(); + return; + } + + us_ticker_int_counter = (uint32_t)(delta >> 16); + us_ticker_int_remainder = (uint16_t)(0xFFFF & delta); + if (us_ticker_int_counter > 0) { + lptmr_set(0xFFFF); + us_ticker_int_counter--; + } else { + lptmr_set(us_ticker_int_remainder); + us_ticker_int_remainder = 0; + } +}