kingkevin
/
stm32f1
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity
stm32f1/lib/onewire_slave.c

410 lines
21 KiB
C
Raw Blame History

/* This program 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 3 of the License, or
* (at your option) any later version.
*
* This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
/** library for 1-wire protocol as master (code)
* @file onewire_slave.c
* @author King Kévin <kingkevin@cuvoodoo.info>
* @date 2017
* @note peripherals used: GPIO and timer @ref onewire_slave_timer, GPIO @ref onewire_slave_gpio
* @note overdrive mode is not supported
* @implements 1-Wire protocol description from Book of iButton Standards
*/
/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdbool.h> // boolean type
#include <stddef.h> // NULL definition
/* STM32 (including CM3) libraries */
#include <libopencmsis/core_cm3.h> // Cortex M3 utilities
#include <libopencm3/cm3/nvic.h> // interrupt handler
#include <libopencm3/stm32/rcc.h> // real-time control clock library
#include <libopencm3/stm32/gpio.h> // general purpose input output library
#include <libopencm3/stm32/timer.h> // timer library
#include <libopencm3/stm32/exti.h> // external interrupt library
/* own libraries */
#include "global.h" // help macros
#include "onewire_slave.h" // own definitions
/** @defgroup onewire_slave_timer timer used to measure 1-wire signal timing
* @{
*/
#define ONEWIRE_SLAVE_TIMER 2 /**< timer ID */
/** @} */
/** @defgroup onewire_slave_gpio GPIO used for 1-wire signal
* @warning ensure no same pin number on other parts are used for external interrupts
* @note external pull-up resistor on pin is required (< 5 kOhm), generally provided by the master
* @{
*/
#define ONEWIRE_SLAVE_PORT A /**< GPIO port */
#define ONEWIRE_SLAVE_PIN 4 /**< GPIO pin */
/** @} */
/** state of 1-Wire communication */
static volatile enum {
ONEWIRE_STATE_IDLE, /**< no current communication */
ONEWIRE_STATE_RESET, /**< reset pulse has been detected */
ONEWIRE_STATE_WAIT_PRESENCE, /**< waiting before sending the presence pulse */
ONEWIRE_STATE_PULSE_PRESENCE, /**< sending the presence pulse */
ONEWIRE_STATE_ROM_COMMAND, /**< slave is reading ROM command bits */
ONEWIRE_STATE_ROM_READ, /**< slave is sending ROM code in response to ROM command READ ROM */
ONEWIRE_STATE_ROM_MATCH, /**< master is sending ROM code to select slave */
ONEWIRE_STATE_ROM_SEARCH_TRUE, /**< master is searching ROM code, slave will send first bit (not negated) */
ONEWIRE_STATE_ROM_SEARCH_FALSE, /**< master is searching ROM code, slave will send first bit (not negated) */
ONEWIRE_STATE_ROM_SEARCH_SELECT, /**< master is searching ROM code, slave will read selected bit */
ONEWIRE_STATE_FUNCTION_COMMAND, /**< slave is reading function command bits */
ONEWIRE_STATE_FUNCTION_DATA, /**< waiting for user to provide data to transfer */
ONEWIRE_STATE_FUNCTION_READ, /**< slave is reading bits */
ONEWIRE_STATE_FUNCTION_WRITE, /**< slave is writing bits */
ONEWIRE_MAX /** to count the number of possible states */
} onewire_slave_state = ONEWIRE_STATE_IDLE;
static uint8_t onewire_slave_rom_code[8] = {0}; /**< slave ROM code */
volatile bool onewire_slave_function_code_received = false;
volatile uint8_t onewire_slave_function_code = 0;
volatile bool onewire_slave_transfer_complete = false;
static volatile uint8_t bits_buffer = 0; /**< buffer for the incoming bits (up to one byte) */
static volatile uint32_t bits_bit = 0; /**< number of incoming bits */
static volatile uint8_t* onewire_slave_transfer_data = NULL; /**< data to transfer (read or write) */
static volatile uint32_t onewire_slave_transfer_bits = 0; /**< number of bits to transfer */
/** compute CRC for 1-Wire
* @note this CRC-8 uses normal polynomial 0x31, reverse polynomial 0x8C, start value 0x00
* @param[in] data bytes on which to calculate CRC checksum on
* @param[in] length number of bytes in data
* @return computed CRC checksum
*/
static uint8_t onewire_slave_crc(uint8_t* data, uint32_t length)
{
if (NULL==data || 0==length) { // check input
return 0; // wrong input
}
uint8_t crc = 0x00; // initial value
for (uint8_t i=0; i<length; i++) { // go through every byte
crc ^= data[i]; // XOR byte
for (uint8_t b=0; b<8; b++) { // go through every bit
if (crc&0x01) { // least significant bit is set (we are using the reverse way)
crc = (crc>>1)^0x8C; // // shift to the right (for the next bit) and XOR with (reverse) polynomial
} else {
crc >>= 1; // just shift right (for the next bit)
}
}
}
return crc;
}
void onewire_slave_setup(uint8_t family, uint64_t serial)
{
// save ROM code (LSB first)
onewire_slave_rom_code[0] = family;
onewire_slave_rom_code[1] = serial >> 40;
onewire_slave_rom_code[2] = serial >> 32;
onewire_slave_rom_code[3] = serial >> 24;
onewire_slave_rom_code[4] = serial >> 16;
onewire_slave_rom_code[5] = serial >> 8;
onewire_slave_rom_code[6] = serial >> 0;
onewire_slave_rom_code[7] = onewire_slave_crc(onewire_slave_rom_code, 7); // calculate CRC
// setup timer to generate/measure signal timing
rcc_periph_clock_enable(RCC_TIM(ONEWIRE_SLAVE_TIMER)); // enable clock for timer peripheral
timer_reset(TIM(ONEWIRE_SLAVE_TIMER)); // reset timer state
timer_set_mode(TIM(ONEWIRE_SLAVE_TIMER), TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); // set timer mode, use undivided timer clock, edge alignment (simple count), and count up
timer_set_prescaler(TIM(ONEWIRE_SLAVE_TIMER), 1-1); // don't use prescale since this 16 bits timer allows to wait > 480 us used for the reset pulse ( 1/(72E6/1/(2**16))=910us )
// use comparator to time signal (without using the output), starting at slot start
timer_set_period(TIM(ONEWIRE_SLAVE_TIMER), 480*(rcc_ahb_frequency/1000000)-1-1300); // minimum time needed for a reset pulse (480 < Trst), plus hand tuning
timer_set_oc_mode(TIM(ONEWIRE_SLAVE_TIMER), TIM_OC1, TIM_OCM_FROZEN);
timer_set_oc_value(TIM(ONEWIRE_SLAVE_TIMER), TIM_OC1, 16*(rcc_ahb_frequency/1000000)-1); // time to wait before sending the presence pulse, after the rising edge of the reset pulse (15 < Tpdh < 60)
timer_set_oc_mode(TIM(ONEWIRE_SLAVE_TIMER), TIM_OC2, TIM_OCM_FROZEN);
timer_set_oc_value(TIM(ONEWIRE_SLAVE_TIMER), TIM_OC2, 45*(rcc_ahb_frequency/1000000)-1-350); // time to sample the bit after being set (1 < Tlow1 < 15, 60 < Tslot < 120), or stop sending the bit use compare function to detect slave presence (15 = Trdv + 0 < Trelease < 45), plus hand tuning
timer_set_oc_value(TIM(ONEWIRE_SLAVE_TIMER), TIM_OC3, 90*(rcc_ahb_frequency/1000000)-1); // time to stop the presence pulse (60 < Tpdl < 120)
timer_clear_flag(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_UIF | TIM_SR_CC1IF | TIM_SR_CC2IF | TIM_SR_CC3IF); // clear all interrupt flags
timer_update_on_overflow(TIM(ONEWIRE_SLAVE_TIMER)); // only use counter overflow as UEV source (use overflow as start time or timeout)
timer_enable_irq(TIM(ONEWIRE_SLAVE_TIMER), TIM_DIER_UIE); // enable update interrupt for overflow
nvic_enable_irq(NVIC_TIM_IRQ(ONEWIRE_SLAVE_TIMER)); // catch interrupt in service routine
onewire_slave_function_code_received = false; // reset state
onewire_slave_state = ONEWIRE_STATE_IDLE; // reset state
onewire_slave_transfer_complete = false; // reset state
// setup GPIO with external interrupt
rcc_periph_clock_enable(RCC_GPIO(ONEWIRE_SLAVE_PORT)); // enable clock for GPIO peripheral
gpio_set(GPIO(ONEWIRE_SLAVE_PORT), GPIO(ONEWIRE_SLAVE_PIN)); // idle is high (using pull-up resistor)
gpio_set_mode(GPIO(ONEWIRE_SLAVE_PORT), GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_OPENDRAIN, GPIO(ONEWIRE_SLAVE_PIN)); // control output using open drain (this mode also allows to read the input signal)
rcc_periph_clock_enable(RCC_AFIO); // enable alternate function clock for external interrupt
exti_select_source(EXTI(ONEWIRE_SLAVE_PIN), GPIO(ONEWIRE_SLAVE_PORT)); // mask external interrupt of this pin only for this port
exti_set_trigger(EXTI(ONEWIRE_SLAVE_PIN), EXTI_TRIGGER_BOTH); // trigger on signal change
exti_enable_request(EXTI(ONEWIRE_SLAVE_PIN)); // enable external interrupt
nvic_enable_irq(NVIC_EXTI_IRQ(ONEWIRE_SLAVE_PIN)); // enable interrupt
}
bool onewire_slave_function_read(uint8_t* data, size_t size)
{
if (NULL==data || 0==size) { // verify input
return false;
}
if (UINT32_MAX/8<size) { // too many bits to transfer
return false;
}
if (onewire_slave_state!=ONEWIRE_STATE_FUNCTION_DATA) { // not in the right state to transfer data
return false;
}
onewire_slave_transfer_data = data; // save buffer to write to
onewire_slave_transfer_bits = size*8; // number of bits to read
onewire_slave_transfer_complete = false; // reset state
bits_bit = 0; // reset number of bits read
onewire_slave_state = ONEWIRE_STATE_FUNCTION_READ; // read data
return true;
}
bool onewire_slave_function_write(const uint8_t* data, size_t size)
{
if (NULL==data || 0==size) { // verify input
return false;
}
if (onewire_slave_state!=ONEWIRE_STATE_FUNCTION_DATA) { // not in the right state to transfer data
return false;
}
if (UINT32_MAX/8<size) { // too many bits to transfer
return false;
}
onewire_slave_transfer_data = (uint8_t*)data; // save buffer to read from
onewire_slave_transfer_bits = size*8; // number of bits to write
onewire_slave_transfer_complete = false; // reset state
bits_bit = 0; // reset number of bits written
bits_buffer = onewire_slave_transfer_data[0]; // prepare byte to write
onewire_slave_state = ONEWIRE_STATE_FUNCTION_WRITE; // write data
return true;
}
/** interrupt service routine called when 1-Wire signal changes */
void EXTI_ISR(ONEWIRE_SLAVE_PIN)(void)
{
exti_reset_request(EXTI(ONEWIRE_SLAVE_PIN)); // reset interrupt
if (gpio_get(GPIO(ONEWIRE_SLAVE_PORT), GPIO(ONEWIRE_SLAVE_PIN))) { // it's a rising edge
switch (onewire_slave_state) {
case ONEWIRE_STATE_RESET: // reset pulse has ended
timer_disable_counter(TIM(ONEWIRE_SLAVE_TIMER)); // stop timer for reconfiguration
timer_set_counter(TIM(ONEWIRE_SLAVE_TIMER), 0); // reset timer counter
timer_clear_flag(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_CC1IF); // clear flag
timer_enable_irq(TIM(ONEWIRE_SLAVE_TIMER), TIM_DIER_CC1IE); // enable compare interrupt for presence pulse
timer_enable_counter(TIM(ONEWIRE_SLAVE_TIMER)); // start timer to generate timing
onewire_slave_state = ONEWIRE_STATE_WAIT_PRESENCE; // set new stated
break;
case ONEWIRE_STATE_PULSE_PRESENCE: // we stopped sending the presence pulse
onewire_slave_state = ONEWIRE_STATE_ROM_COMMAND; // we now expect a ROM command
bits_bit = 0; // reset buffer bit count
break; // no need to stop the time, the reset will be checked correctly
default: // rising edge is not important is the other cases
break; // nothing to do
}
} else { // it's a falling edge, the beginning of a new signal
timer_disable_counter(TIM(ONEWIRE_SLAVE_TIMER)); // stop timer for reconfiguration
timer_set_counter(TIM(ONEWIRE_SLAVE_TIMER), 0); // reset timer counter
timer_disable_irq(TIM(ONEWIRE_SLAVE_TIMER), TIM_DIER_CC1IE | TIM_DIER_CC2IE | TIM_DIER_CC3IE); // disable all timers
switch (onewire_slave_state) {
case ONEWIRE_STATE_PULSE_PRESENCE: // we started sending the presence pulse
timer_enable_irq(TIM(ONEWIRE_SLAVE_TIMER), TIM_DIER_CC3IE); // enable timer for end of pulse
break;
case ONEWIRE_STATE_ROM_COMMAND: // read ROM command bits
case ONEWIRE_STATE_ROM_MATCH: // read ROM code bits
case ONEWIRE_STATE_FUNCTION_COMMAND: // read function command bits
case ONEWIRE_STATE_ROM_SEARCH_SELECT: // read selected ROM code bit
case ONEWIRE_STATE_FUNCTION_READ: // read function data bit
timer_enable_irq(TIM(ONEWIRE_SLAVE_TIMER), TIM_DIER_CC2IE); // enable timer for reading bit
break;
case ONEWIRE_STATE_ROM_READ: // send ROM code bit
case ONEWIRE_STATE_ROM_SEARCH_TRUE: // send ROM code bit while searching ROM, not negated
case ONEWIRE_STATE_ROM_SEARCH_FALSE: // send ROM code bit while searching ROM, already negated
case ONEWIRE_STATE_FUNCTION_WRITE: // write function data bit
timer_enable_irq(TIM(ONEWIRE_SLAVE_TIMER), TIM_DIER_CC2IE); // enable timer for reading bit
if (0==(bits_buffer&(1<<(bits_bit%8)))) { // need to send a 0 bit
gpio_clear(GPIO(ONEWIRE_SLAVE_PORT), GPIO(ONEWIRE_SLAVE_PIN)); // hold low to send 0 bit
}
break;
case ONEWIRE_STATE_IDLE: // we only expect a reset
default: // we don't expect any falling edge in other states
onewire_slave_state = ONEWIRE_STATE_IDLE; // unexpected signal, reset to idle state
break; // the timer overflow will confirm detect reset pulses
}
timer_clear_flag(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_UIF | TIM_SR_CC1IF | TIM_SR_CC2IF | TIM_SR_CC3IF); // clear all flags
timer_enable_counter(TIM(ONEWIRE_SLAVE_TIMER)); // start timer to measure the configured timeouts
}
}
/** interrupt service routine called for timer */
void TIM_ISR(ONEWIRE_SLAVE_TIMER)(void)
{
if (timer_interrupt_source(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_UIF)) { // reset timer triggered, verify if it's a reset
if (0==gpio_get(GPIO(ONEWIRE_SLAVE_PORT), GPIO(ONEWIRE_SLAVE_PIN))) { // signal it still low, thus it must be a reset
onewire_slave_state = ONEWIRE_STATE_RESET; // update state
}
timer_disable_counter(TIM(ONEWIRE_SLAVE_TIMER)); // stop timer since there is nothing more to measure
timer_disable_irq(TIM(ONEWIRE_SLAVE_TIMER), TIM_DIER_CC1IE | TIM_DIER_CC2IE | TIM_DIER_CC3IE); // disable all timers
timer_clear_flag(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_UIF | TIM_SR_CC1IF | TIM_SR_CC2IF | TIM_SR_CC3IF); // clear all flag (I have no idea why the others are get too, even when the interrupt is not enabled)
}
if (timer_interrupt_source(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_CC1IF)) { // wait for presence pulse timer triggered
timer_clear_flag(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_CC1IF); // clear flag
if (ONEWIRE_STATE_WAIT_PRESENCE==onewire_slave_state) { // we can now send the pulse
onewire_slave_state = ONEWIRE_STATE_PULSE_PRESENCE; // save new state
gpio_clear(GPIO(ONEWIRE_SLAVE_PORT), GPIO(ONEWIRE_SLAVE_PIN)); // send presence pulse (will also trigger the timer start)
}
}
if (timer_interrupt_source(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_CC2IF)) { // time to read the bit, or stop writing it
// read/write bit depending on bit
switch (onewire_slave_state) {
case ONEWIRE_STATE_ROM_COMMAND: // read ROM command code bit
case ONEWIRE_STATE_ROM_MATCH: // read ROM code
case ONEWIRE_STATE_FUNCTION_COMMAND: // read function command code bit
case ONEWIRE_STATE_ROM_SEARCH_SELECT: // read selected ROM code bit
case ONEWIRE_STATE_FUNCTION_READ: // read function data bit
if (gpio_get(GPIO(ONEWIRE_SLAVE_PORT), GPIO(ONEWIRE_SLAVE_PIN))) { // bit is set to 1
bits_buffer |= (1<<(bits_bit%8)); // set bit
} else { // bit is set to 0
bits_buffer &= ~(1<<(bits_bit%8)); // clear bit
}
bits_bit++; // go to next bit
break;
case ONEWIRE_STATE_ROM_READ: // write ROM code
case ONEWIRE_STATE_FUNCTION_WRITE: // write function data bit
gpio_set(GPIO(ONEWIRE_SLAVE_PORT), GPIO(ONEWIRE_SLAVE_PIN)); // stop sending bit
bits_bit++; // go to next bit
break;
case ONEWIRE_STATE_ROM_SEARCH_TRUE: // ROM code bit is sent
case ONEWIRE_STATE_ROM_SEARCH_FALSE: // ROM code bit is sent
gpio_set(GPIO(ONEWIRE_SLAVE_PORT), GPIO(ONEWIRE_SLAVE_PIN)); // stop sending bit
break;
default: // these states don't need read/write
break;
}
static uint8_t rom_code_byte; // which byte of the ROM code is processed
// act on bit count
switch (onewire_slave_state) {
case ONEWIRE_STATE_ROM_COMMAND: // read ROM command
if (bits_bit>7) { // complete ROM command code received
bits_bit = 0; // reset buffer
rom_code_byte = 0; // reset ROM code byte index
switch (bits_buffer) { // act depending on ROM command code
case 0x33: // READ ROM
bits_buffer = onewire_slave_rom_code[rom_code_byte]; // prepare to send the first byte
onewire_slave_state = ONEWIRE_STATE_ROM_READ; // write ROM code
break;
case 0xcc: // SKIP ROM
onewire_slave_state = ONEWIRE_STATE_FUNCTION_COMMAND; // now read function command code
break;
case 0x55: // MATCH ROM
onewire_slave_state = ONEWIRE_STATE_ROM_MATCH; // read ROM code
break;
case 0xf0: // SEARCH ROM
bits_buffer = onewire_slave_rom_code[rom_code_byte]; // prepare to search code
onewire_slave_state = ONEWIRE_STATE_ROM_SEARCH_TRUE; // prepare to start sending first new bit
break;
default: // unknown ROM code
onewire_slave_state = ONEWIRE_STATE_IDLE; // go back to default idle state
break;
}
}
break;
case ONEWIRE_STATE_ROM_READ: // send ROM code
if (bits_bit>7) { // complete byte transmitted
rom_code_byte++; // go to next ROM code byte
if (rom_code_byte>LENGTH(onewire_slave_rom_code)) { // complete ROM code send
onewire_slave_state = ONEWIRE_STATE_IDLE; // go back to default idle state
} else {
bits_bit = 0; // reset buffer
bits_buffer = onewire_slave_rom_code[rom_code_byte]; // send next ROM code byte
}
}
break;
case ONEWIRE_STATE_ROM_MATCH: // compare ROM code
if (bits_bit>7) { // complete byte received
if (bits_buffer==onewire_slave_rom_code[rom_code_byte]) { // ROM code byte matches
bits_bit = 0; // reset buffer
rom_code_byte++; // go to next ROM code byte
if (rom_code_byte>=LENGTH(onewire_slave_rom_code)) { // complete ROM code matches
onewire_slave_state = ONEWIRE_STATE_FUNCTION_COMMAND; // now read function command code
}
} else { // ROM code does not match
onewire_slave_state = ONEWIRE_STATE_IDLE; // stop comparing and go back to idle
}
}
break;
case ONEWIRE_STATE_ROM_SEARCH_TRUE: // ROM code bit is send, prepare to send negated version
bits_buffer ^= (1<<bits_bit); // negate bit
onewire_slave_state = ONEWIRE_STATE_ROM_SEARCH_FALSE; // send negated version
break;
case ONEWIRE_STATE_ROM_SEARCH_FALSE: // negated ROM code bit is send, prepare to read selected bit
onewire_slave_state = ONEWIRE_STATE_ROM_SEARCH_SELECT; // read selected
break;
case ONEWIRE_STATE_ROM_SEARCH_SELECT: // check if we are selected
if ((bits_buffer&(1<<(bits_bit-1)))==(onewire_slave_rom_code[rom_code_byte]&(1<<(bits_bit-1)))) { // we have been selected
onewire_slave_state = ONEWIRE_STATE_ROM_SEARCH_TRUE; // prepare to compare next bit
} else { // we are no selected
onewire_slave_state = ONEWIRE_STATE_IDLE; // go back to idle
}
if (bits_bit>7) { // complete byte searched
bits_bit = 0; // reset buffer
rom_code_byte++; // go to next ROM code byte
if (rom_code_byte>=LENGTH(onewire_slave_rom_code)) { // complete ROM code search
onewire_slave_state = ONEWIRE_STATE_FUNCTION_COMMAND; // now read function command code
} else {
bits_buffer = onewire_slave_rom_code[rom_code_byte]; // prepare next ROM code byte
}
}
break;
case ONEWIRE_STATE_FUNCTION_COMMAND: // read function command
if (bits_bit>7) { // complete function command code received
onewire_slave_function_code = bits_buffer; // save function command code to user buffer
onewire_slave_state = ONEWIRE_STATE_FUNCTION_DATA; // let the user transfer data
onewire_slave_function_code_received = true; // notify user
}
break;
case ONEWIRE_STATE_FUNCTION_READ: // save function data bit
if (0==bits_bit%8) { // complete byte received
onewire_slave_transfer_data[(bits_bit-1)/8] = bits_buffer; // save received bytes
}
if (bits_bit>=onewire_slave_transfer_bits) { // read transfer complete
onewire_slave_transfer_data[(bits_bit-1)/8] = bits_buffer; // save last bits
onewire_slave_state = ONEWIRE_STATE_FUNCTION_DATA; // let the user transfer more data
onewire_slave_transfer_complete = true; // notify user
}
break;
case ONEWIRE_STATE_FUNCTION_WRITE: // update function data bit to write
if (0==bits_bit%8) { // complete byte transfer
bits_buffer = onewire_slave_transfer_data[bits_bit/8]; // prepare next byte to write
}
if (bits_bit>=onewire_slave_transfer_bits) { // write transfer complete
onewire_slave_state = ONEWIRE_STATE_FUNCTION_DATA; // let the user transfer more data
onewire_slave_transfer_complete = true; // notify user
}
break;
default: // no action needed
break;
}
timer_clear_flag(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_CC2IF); // clear flag
}
if (timer_interrupt_source(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_CC3IF)) { // end of presence pulse timer triggered
timer_clear_flag(TIM(ONEWIRE_SLAVE_TIMER), TIM_SR_CC3IF); // clear flag
if (ONEWIRE_STATE_PULSE_PRESENCE==onewire_slave_state) {
gpio_set(GPIO(ONEWIRE_SLAVE_PORT), GPIO(ONEWIRE_SLAVE_PIN)); // stop sending presence pulse
// if the pin stays low the reset timer will catch it
}
}
}
Reference in New Issue View Git Blame Copy Permalink