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Add more documentation for onewire.h

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This commit is contained in:
Alex Stewart 2016-03-17 19:24:29 -07:00
parent 9b49b426f6
commit 9c37da6834
2 changed files with 217 additions and 110 deletions
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53
extras/onewire/onewire.c
View file

@ -3,6 +3,10 @@
#include "task.h"
#include "esp/gpio.h"
#define ONEWIRE_SELECT_ROM 0x55
#define ONEWIRE_SKIP_ROM 0xcc
#define ONEWIRE_SEARCH 0xf0
// Waits up to `max_wait` microseconds for the specified pin to go high.
// Returns true if successful, false if the bus never comes high (likely
// shorted).
@ -48,9 +52,9 @@ bool onewire_reset(int pin) {
return r;
}
static bool _onewire_write_bit(int pin, uint8_t v) {
static bool _onewire_write_bit(int pin, bool v) {
if (!_onewire_wait_for_bus(pin, 10)) return false;
if (v & 1) {
if (v) {
taskENTER_CRITICAL();
gpio_write(pin, 0); // drive output low
sdk_os_delay_us(10);
@ -94,7 +98,7 @@ bool onewire_write(int pin, uint8_t v) {
uint8_t bitMask;
for (bitMask = 0x01; bitMask; bitMask <<= 1) {
if (!_onewire_write_bit(pin, (bitMask & v)?1:0)) {
if (!_onewire_write_bit(pin, (bitMask & v))) {
return false;
}
}
@ -142,28 +146,36 @@ bool onewire_read_bytes(int pin, uint8_t *buf, size_t count) {
return true;
}
// Do a ROM select
//
void onewire_select(int pin, onewire_addr_t rom) {
bool onewire_select(int pin, onewire_addr_t addr) {
uint8_t i;
onewire_write(pin, 0x55); // Choose ROM
if (!onewire_write(pin, ONEWIRE_SELECT_ROM)) {
return false;
}
for (i = 0; i < 8; i++) {
onewire_write(pin, rom & 0xff);
rom >>= 8;
if (!onewire_write(pin, addr & 0xff)) {
return false;
}
addr >>= 8;
}
return true;
}
// Do a ROM skip
//
void onewire_skip_rom(int pin) {
onewire_write(pin, 0xCC); // Skip ROM
bool onewire_skip_rom(int pin) {
return onewire_write(pin, ONEWIRE_SKIP_ROM);
}
void onewire_power(int pin) {
bool onewire_power(int pin) {
// Make sure the bus is not being held low before driving it high, or we
// may end up shorting ourselves out.
if (!_onewire_wait_for_bus(pin, 10)) return false;
gpio_enable(pin, GPIO_OUTPUT);
gpio_write(pin, 1);
return true;
}
void onewire_depower(int pin) {
@ -175,9 +187,6 @@ void onewire_search_start(onewire_search_t *search) {
memset(search, 0, sizeof(*search));
}
// Setup the search to find the device type 'family_code' on the next call
// to search(*newAddr) if it is present.
//
void onewire_search_prefix(onewire_search_t *search, uint8_t family_code) {
uint8_t i;
@ -209,8 +218,8 @@ onewire_addr_t onewire_search_next(onewire_search_t *search, int pin) {
int rom_byte_number;
uint8_t id_bit, cmp_id_bit;
onewire_addr_t addr;
unsigned char rom_byte_mask, search_direction;
unsigned char rom_byte_mask;
bool search_direction;
// initialize for search
id_bit_number = 1;
@ -230,7 +239,7 @@ onewire_addr_t onewire_search_next(onewire_search_t *search, int pin) {
}
// issue the search command
onewire_write(pin, 0xF0);
onewire_write(pin, ONEWIRE_SEARCH);
// loop to do the search
do {
@ -259,14 +268,14 @@ onewire_addr_t onewire_search_next(onewire_search_t *search, int pin) {
}
// if 0 was picked then record its position in LastZero
if (search_direction == 0) {
if (!search_direction) {
last_zero = id_bit_number;
}
}
// set or clear the bit in the ROM byte rom_byte_number
// with mask rom_byte_mask
if (search_direction == 1) {
if (search_direction) {
search->rom_no[rom_byte_number] |= rom_byte_mask;
} else {
search->rom_no[rom_byte_number] &= ~rom_byte_mask;