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can_arch.c
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can_arch.c
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/*
* Copyright (C) 2012 Piotr Esden-Tempski <piotr@esden.net>
*
* This file is part of paparazzi.
*
* paparazzi is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* paparazzi is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with paparazzi; see the file COPYING. If not, write to
* the Free Software Foundation, 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*
*/
/**
* @file arch/stm32/mcu_periph/can_arch.c
* @ingroup stm32_arch
*
* Handling of CAN hardware for STM32.
*/
#include <stdint.h>
#include <string.h>
#include "mcu_periph/can_arch.h"
#include "mcu_periph/can.h"
#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/can.h>
#include <libopencm3/cm3/nvic.h>
#include "led.h"
#ifndef STM32F1
#error "CAN is currently only implemented for STM32F1"
#endif
#ifdef RTOS_PRIO
#define NVIC_USB_LP_CAN_RX0_IRQ_PRIO RTOS_PRIO+1
#else
#define NVIC_USB_LP_CAN_RX0_IRQ_PRIO 1
#endif
void _can_run_rx_callback(uint32_t id, uint8_t *buf, uint8_t len);
bool can_initialized = false;
void can_hw_init(void)
{
/* Enable peripheral clocks. */
rcc_periph_clock_enable(RCC_AFIO);
rcc_periph_clock_enable(RCC_GPIOB);
rcc_periph_clock_enable(RCC_CAN1);
/* Remap the gpio pin if necessary. */
AFIO_MAPR |= AFIO_MAPR_CAN1_REMAP_PORTB;
/* Configure CAN pin: RX (input pull-up). */
gpio_set_mode(GPIO_BANK_CAN1_PB_RX, GPIO_MODE_INPUT,
GPIO_CNF_INPUT_PULL_UPDOWN, GPIO_CAN1_PB_RX);
gpio_set(GPIO_BANK_CAN1_PB_RX, GPIO_CAN1_PB_RX);
/* Configure CAN pin: TX (output push-pull). */
gpio_set_mode(GPIO_BANK_CAN1_PB_TX, GPIO_MODE_OUTPUT_50_MHZ,
GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_CAN1_PB_TX);
/* NVIC setup. */
nvic_enable_irq(NVIC_USB_LP_CAN_RX0_IRQ);
nvic_set_priority(NVIC_USB_LP_CAN_RX0_IRQ, NVIC_USB_LP_CAN_RX0_IRQ_PRIO);
/* Reset CAN. */
can_reset(CAN1);
/* CAN cell init.
* For time quanta calculation see STM32 reference manual
* section 24.7.7 "Bit timing" page 645
*
* To talk to CSC using LPC mcu we need a baud rate of 375kHz
* The APB1 runs at 36MHz therefor we select a prescaler of 12
* resulting in time quanta frequency of 36MHz / 12 = 3MHz
*
* As the Bit time is combined of 1tq for SYNC_SEG, TS1tq for bit
* segment 1 and TS2tq for bit segment 2:
* BITtq = 1tq + TS1tq + TS2tq
*
* We can choose to use TS1 = 3 and TS2 = 4 getting
* 1tq + 3tq + 4tq = 8tq per bit therefor a bit frequency is
* 3MHZ / 8 = 375kHz
*
* Maximum baud rate of CAN is 1MHz so we can choose to use
* prescaler of 2 resulting in a quanta frequency of 36MHz / 2 = 18Mhz
*
* So we need to devide the frequency by 18. This can be accomplished
* using TS1 = 10 and TS2 = 7 resulting in:
* 1tq + 10tq + 7tq = 18tq
*
* NOTE: Although it is out of spec I managed to have CAN run at 2MBit
* Just decrease the prescaler to 1. It worked for me(tm) (esden)
*/
if (can_init(CAN1,
false, /* TTCM: Time triggered comm mode? */
true, /* ABOM: Automatic bus-off management? */
false, /* AWUM: Automatic wakeup mode? */
false, /* NART: No automatic retransmission? */
false, /* RFLM: Receive FIFO locked mode? */
false, /* TXFP: Transmit FIFO priority? */
CAN_BTR_SJW_1TQ,
CAN_BTR_TS1_10TQ,
CAN_BTR_TS2_7TQ,
2, /* BRP+1: Baud rate prescaler */
false, /* loopback mode */
false)) /* silent mode */
{
/* TODO we need something somewhere where we can leave a note
* that CAN was unable to initialize. Just like any other
* driver should...
*/
can_reset(CAN1);
return;
}
/* CAN filter 0 init. */
can_filter_id_mask_32bit_init(CAN1,
0, /* Filter ID */
0, /* CAN ID */
0, /* CAN ID mask */
0, /* FIFO assignment (here: FIFO0) */
true); /* Enable the filter. */
/* Enable CAN RX interrupt. */
can_enable_irq(CAN1, CAN_IER_FMPIE0);
/* Remember that we succeeded to initialize. */
can_initialized = true;
}
int can_hw_transmit(uint32_t id, const uint8_t *buf, uint8_t len)
{
if (!can_initialized) {
return -2;
}
if(len > 8){
return -1;
}
/* FIXME: we are discarding the const qualifier for buf here.
* We should probably fix libopencm3 to actually have the
* const qualifier too...
*/
return can_transmit(CAN1,
id, /* (EX/ST)ID: CAN ID */
#ifdef USE_CAN_EXT_ID
true, /* IDE: CAN ID extended */
#else
false, /* IDE: CAN ID not extended */
#endif
false, /* RTR: Request transmit? */
len, /* DLC: Data length */
(uint8_t *)buf);
}
void usb_lp_can_rx0_isr(void)
{
uint32_t id, fmi;
bool ext, rtr;
uint8_t length, data[8];
can_receive(CAN1,
0, /* FIFO: 0 */
false, /* Release */
&id,
&ext,
&rtr,
&fmi,
&length,
data);
_can_run_rx_callback(id, data, length);
can_fifo_release(CAN1, 0);
}