esphome/esphome/components/dallas/esp_one_wire.cpp

253 lines
6.5 KiB
C++

#include "esp_one_wire.h"
#include "esphome/core/log.h"
#include "esphome/core/helpers.h"
namespace esphome {
namespace dallas {
static const char *const TAG = "dallas.one_wire";
const uint8_t ONE_WIRE_ROM_SELECT = 0x55;
const int ONE_WIRE_ROM_SEARCH = 0xF0;
ESPOneWire::ESPOneWire(InternalGPIOPin *pin) { pin_ = pin->to_isr(); }
bool HOT IRAM_ATTR ESPOneWire::reset() {
// See reset here:
// https://www.maximintegrated.com/en/design/technical-documents/app-notes/1/126.html
// Wait for communication to clear (delay G)
pin_.pin_mode(gpio::FLAG_INPUT | gpio::FLAG_PULLUP);
uint8_t retries = 125;
do {
if (--retries == 0)
return false;
delayMicroseconds(2);
} while (!pin_.digital_read());
// Send 480µs LOW TX reset pulse (drive bus low, delay H)
pin_.pin_mode(gpio::FLAG_OUTPUT);
pin_.digital_write(false);
delayMicroseconds(480);
// Release the bus, delay I
pin_.pin_mode(gpio::FLAG_INPUT | gpio::FLAG_PULLUP);
delayMicroseconds(70);
// sample bus, 0=device(s) present, 1=no device present
bool r = !pin_.digital_read();
// delay J
delayMicroseconds(410);
return r;
}
void HOT IRAM_ATTR ESPOneWire::write_bit(bool bit) {
// drive bus low
pin_.pin_mode(gpio::FLAG_OUTPUT);
pin_.digital_write(false);
// from datasheet:
// write 0 low time: t_low0: min=60µs, max=120µs
// write 1 low time: t_low1: min=1µs, max=15µs
// time slot: t_slot: min=60µs, max=120µs
// recovery time: t_rec: min=1µs
// ds18b20 appears to read the bus after roughly 14µs
uint32_t delay0 = bit ? 6 : 60;
uint32_t delay1 = bit ? 54 : 5;
// delay A/C
delayMicroseconds(delay0);
// release bus
pin_.digital_write(true);
// delay B/D
delayMicroseconds(delay1);
}
bool HOT IRAM_ATTR ESPOneWire::read_bit() {
// drive bus low
pin_.pin_mode(gpio::FLAG_OUTPUT);
pin_.digital_write(false);
// note: for reading we'll need very accurate timing, as the
// timing for the digital_read() is tight; according to the datasheet,
// we should read at the end of 16µs starting from the bus low
// typically, the ds18b20 pulls the line high after 11µs for a logical 1
// and 29µs for a logical 0
uint32_t start = micros();
// datasheet says >1µs
delayMicroseconds(3);
// release bus, delay E
pin_.pin_mode(gpio::FLAG_INPUT | gpio::FLAG_PULLUP);
// Unfortunately some frameworks have different characteristics than others
// esp32 arduino appears to pull the bus low only after the digital_write(false),
// whereas on esp-idf it already happens during the pin_mode(OUTPUT)
// manually correct for this with these constants.
#ifdef USE_ESP32
uint32_t timing_constant = 12;
#else
uint32_t timing_constant = 14;
#endif
// measure from start value directly, to get best accurate timing no matter
// how long pin_mode/delayMicroseconds took
while (micros() - start < timing_constant)
;
// sample bus to read bit from peer
bool r = pin_.digital_read();
// read slot is at least 60µs; get as close to 60µs to spend less time with interrupts locked
uint32_t now = micros();
if (now - start < 60)
delayMicroseconds(60 - (now - start));
return r;
}
void IRAM_ATTR ESPOneWire::write8(uint8_t val) {
for (uint8_t i = 0; i < 8; i++) {
this->write_bit(bool((1u << i) & val));
}
}
void IRAM_ATTR ESPOneWire::write64(uint64_t val) {
for (uint8_t i = 0; i < 64; i++) {
this->write_bit(bool((1ULL << i) & val));
}
}
uint8_t IRAM_ATTR ESPOneWire::read8() {
uint8_t ret = 0;
for (uint8_t i = 0; i < 8; i++) {
ret |= (uint8_t(this->read_bit()) << i);
}
return ret;
}
uint64_t IRAM_ATTR ESPOneWire::read64() {
uint64_t ret = 0;
for (uint8_t i = 0; i < 8; i++) {
ret |= (uint64_t(this->read_bit()) << i);
}
return ret;
}
void IRAM_ATTR ESPOneWire::select(uint64_t address) {
this->write8(ONE_WIRE_ROM_SELECT);
this->write64(address);
}
void IRAM_ATTR ESPOneWire::reset_search() {
this->last_discrepancy_ = 0;
this->last_device_flag_ = false;
this->rom_number_ = 0;
}
uint64_t IRAM_ATTR ESPOneWire::search() {
if (this->last_device_flag_) {
return 0u;
}
{
InterruptLock lock;
if (!this->reset()) {
// Reset failed or no devices present
this->reset_search();
return 0u;
}
}
uint8_t id_bit_number = 1;
uint8_t last_zero = 0;
uint8_t rom_byte_number = 0;
bool search_result = false;
uint8_t rom_byte_mask = 1;
{
InterruptLock lock;
// Initiate search
this->write8(ONE_WIRE_ROM_SEARCH);
do {
// read bit
bool id_bit = this->read_bit();
// read its complement
bool cmp_id_bit = this->read_bit();
if (id_bit && cmp_id_bit) {
// No devices participating in search
break;
}
bool branch;
if (id_bit != cmp_id_bit) {
// only chose one branch, the other one doesn't have any devices.
branch = id_bit;
} else {
// there are devices with both 0s and 1s at this bit
if (id_bit_number < this->last_discrepancy_) {
branch = (this->rom_number8_()[rom_byte_number] & rom_byte_mask) > 0;
} else {
branch = id_bit_number == this->last_discrepancy_;
}
if (!branch) {
last_zero = id_bit_number;
}
}
if (branch) {
// set bit
this->rom_number8_()[rom_byte_number] |= rom_byte_mask;
} else {
// clear bit
this->rom_number8_()[rom_byte_number] &= ~rom_byte_mask;
}
// choose/announce branch
this->write_bit(branch);
id_bit_number++;
rom_byte_mask <<= 1;
if (rom_byte_mask == 0u) {
// go to next byte
rom_byte_number++;
rom_byte_mask = 1;
}
} while (rom_byte_number < 8); // loop through all bytes
}
if (id_bit_number >= 65) {
this->last_discrepancy_ = last_zero;
if (this->last_discrepancy_ == 0) {
// we're at root and have no choices left, so this was the last one.
this->last_device_flag_ = true;
}
search_result = true;
}
search_result = search_result && (this->rom_number8_()[0] != 0);
if (!search_result) {
this->reset_search();
return 0u;
}
return this->rom_number_;
}
std::vector<uint64_t> ESPOneWire::search_vec() {
std::vector<uint64_t> res;
this->reset_search();
uint64_t address;
while ((address = this->search()) != 0u)
res.push_back(address);
return res;
}
void IRAM_ATTR ESPOneWire::skip() {
this->write8(0xCC); // skip ROM
}
uint8_t IRAM_ATTR *ESPOneWire::rom_number8_() { return reinterpret_cast<uint8_t *>(&this->rom_number_); }
} // namespace dallas
} // namespace esphome