diff options
Diffstat (limited to 'nuttx/arch/avr/src/at90usb/at90usb_timerisr.c')
| -rw-r--r-- | nuttx/arch/avr/src/at90usb/at90usb_timerisr.c | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/nuttx/arch/avr/src/at90usb/at90usb_timerisr.c b/nuttx/arch/avr/src/at90usb/at90usb_timerisr.c new file mode 100644 index 000000000..079433b8d --- /dev/null +++ b/nuttx/arch/avr/src/at90usb/at90usb_timerisr.c @@ -0,0 +1,165 @@ +/**************************************************************************** + * arch/avr/src/at90usb/at90usb_timerisr.c + * + * Copyright (C) 2011 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <spudmonkey@racsa.co.cr> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name NuttX nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ****************************************************************************/ + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <nuttx/config.h> + +#include <stdint.h> +#include <time.h> +#include <debug.h> + +#include <nuttx/arch.h> +#include <arch/board/board.h> +#include <avr/io.h> + +#include "up_arch.h" + +#include "at90usb_internal.h" + +/**************************************************************************** + * Definitions + ****************************************************************************/ + +/* The CPU frequency is given by BOARD_CPU_CLOCK (defined in board.h). The + * desired interrupt frequency is given by CONFIG_MSEC_PER_TICK. An unscaled + * ideal match is given by: + * + * CLOCK = CPU_CLOCK / DIVISOR # CPU clocks/sec + * MATCH = CLOCK / CLOCKS_PER_SEC # CPU clocks/timer tick + * MATCH = CPU_CLOCK / DIVISOR / CLOCKS_PER_SEC # CPU clocks/timer tick + * + * But we only have 16-bits of accuracy so we need to pick the smallest + * divisor using the following brute force calculation: + */ + +#define MATCH1 (( BOARD_CPU_CLOCK + CLOCKS_PER_SEC/2) / CLOCKS_PER_SEC) +#define MATCH8 ((((BOARD_CPU_CLOCK + 4) / 8) + CLOCKS_PER_SEC/2) / CLOCKS_PER_SEC) +#define MATCH64 ((((BOARD_CPU_CLOCK + 8) / 64) + CLOCKS_PER_SEC/2) / CLOCKS_PER_SEC) +#define MATCH256 ((((BOARD_CPU_CLOCK + 128) / 256) + CLOCKS_PER_SEC/2) / CLOCKS_PER_SEC) +#define MATCH1024 ((((BOARD_CPU_CLOCK + 512) / 1024) + CLOCKS_PER_SEC/2) / CLOCKS_PER_SEC) + +#if MATCH1 <= 65536 +# define MATCH (MATCH1-1) +# define PRESCALE 1 +#elif MATCH8 <= 65536 +# define MATCH (MATCH8-1) +# define PRESCALE 2 +#elif MATCH64 <= 65536 +# define MATCH (MATCH64-1) +# define PRESCALE 3 +#elif MATCH256 <= 65536 +# define MATCH (MATCH256-1) +# define PRESCALE 4 +#elif MATCH1024 <= 65536 +# define MATCH (MATCH1024-1) +# define PRESCALE 5 +#else +# error "Cannot represent this timer frequency" +#endif + +/* + * Eg. CPU_CLOCK = 8MHz, CLOCKS_PER_SEC = 100 + * + * MATCH1 ((8000000 + 50) / 100) = 80,000 FREQ=100.0Hz + * MATCH8 ((1000000 + 50) / 100) = 10,000 FREQ=100.0Hz <-- this one + * MATCH64 (( 125000 + 50) / 100) = 1,250 FREQ=100.0Hz + * MATCH256 (( 31250 + 50) / 100) = 313 FREQ=99.8Hz + * MATCH1024 (( 7804 + 50) / 100) = 78 FREQ=100.1Hz + */ + +/**************************************************************************** + * Private Types + ****************************************************************************/ + +/**************************************************************************** + * Private Functions + ****************************************************************************/ + +/**************************************************************************** + * Global Functions + ****************************************************************************/ + +/**************************************************************************** + * Function: up_timerisr + * + * Description: + * The timer ISR will perform a variety of services for various portions + * of the systems. + * + ****************************************************************************/ + +int up_timerisr(int irq, uint32_t *regs) +{ + /* Process timer interrupt */ + + sched_process_timer(); + return 0; +} + +/**************************************************************************** + * Function: up_timerinit + * + * Description: + * This function is called during start-up to initialize the timer + * interrupt. NOTE: This function depends on setup of OSC32 by + * up_clkinitialize(). + * + ****************************************************************************/ + +void up_timerinit(void) +{ + /* Setup timer 1 compare match A to generate a tick interrupt. + * + * First, setup the match value for compare match A. + */ + + OCR1AH = (uint8_t)((uint16_t)MATCH >> 8); + OCR1AL = (uint8_t)((uint16_t)MATCH & 0xff); + + /* Setup clock source and compare match behaviour. */ + + TCCR1A = 0x08 | PRESCALE; + + /* Attach the timer interrupt vector */ + + (void)irq_attach(AT90USB_IRQ_T2COMPA, (xcpt_t)up_timerisr); + + /* Enable the interrupt on compare match A */ + + TIMSK1 |= 0x10; +} |