From 3280c7d177f07282ecd72b9aa881325136b55569 Mon Sep 17 00:00:00 2001
From: "Christian W. Zuckschwerdt" <christian@zuckschwerdt.org>
Date: Mon, 1 Oct 2018 14:28:21 +0000
Subject: [PATCH] Add W1_PARASITE_POWER optimization for DS18X20

---
 sonoff/user_config.h       |  1 +
 sonoff/xsns_05_ds18x20.ino | 27 ++++++++++++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/sonoff/user_config.h b/sonoff/user_config.h
index 72aa97d53..ee77854bc 100644
--- a/sonoff/user_config.h
+++ b/sonoff/user_config.h
@@ -271,6 +271,7 @@
 // -- One wire sensors ----------------------------
                                                  // WARNING: Select none for default one DS18B20 sensor or enable one of the following two options for multiple sensors
 #define USE_DS18x20                              // Optional for more than one DS18x20 sensors with id sort, single scan and read retry (+1k3 code)
+//#define W1_PARASITE_POWER                        // If using USE_DS18x20 then optimize for parasite powered sensors
 //#define USE_DS18x20_LEGACY                       // Optional for more than one DS18x20 sensors with dynamic scan using library OneWire (+1k5 code)
 
 // -- I2C sensors ---------------------------------
diff --git a/sonoff/xsns_05_ds18x20.ino b/sonoff/xsns_05_ds18x20.ino
index 869deac8e..474f26e2e 100644
--- a/sonoff/xsns_05_ds18x20.ino
+++ b/sonoff/xsns_05_ds18x20.ino
@@ -49,6 +49,10 @@ struct DS18X20STRUCT {
 uint8_t ds18x20_sensors = 0;
 uint8_t ds18x20_pin = 0;
 char ds18x20_types[12];
+#ifdef W1_PARASITE_POWER
+uint8_t ds18x20_sensor_curr = 0;
+unsigned long w1_power_until = 0;
+#endif
 
 /*********************************************************************************************\
  * Embedded tuned OneWire library
@@ -285,7 +289,14 @@ void Ds18x20Init()
 void Ds18x20Convert()
 {
   OneWireReset();
+#ifdef W1_PARASITE_POWER
+  // With parasite power address one sensor at a time
+  if (++ds18x20_sensor_curr >= ds18x20_sensors)
+    ds18x20_sensor_curr = 0;
+  OneWireSelect(ds18x20_sensor[ds18x20_sensor_curr].address);
+#else
   OneWireWrite(W1_SKIP_ROM);           // Address all Sensors on Bus
+#endif
   OneWireWrite(W1_CONVERT_TEMP);       // start conversion, no parasite power on at the end
 //  delay(750);                          // 750ms should be enough for 12bit conv
 }
@@ -334,6 +345,9 @@ bool Ds18x20Read(uint8_t sensor)
           OneWireWrite(data[4]);          // Configuration Register
           OneWireSelect(ds18x20_sensor[index].address);
           OneWireWrite(W1_WRITE_EEPROM);  // Save scratchpad to EEPROM
+#ifdef W1_PARASITE_POWER
+          w1_power_until = millis() + 10; // 10ms specified duration for EEPROM write
+#endif
         }
         temp12 = (data[1] << 8) + data[0];
         if (temp12 > 2047) {
@@ -374,7 +388,18 @@ void Ds18x20Name(uint8_t sensor)
 
 void Ds18x20EverySecond()
 {
-  if (uptime &1) {
+#ifdef W1_PARASITE_POWER
+  // skip access if there is still an eeprom write ongoing
+  unsigned long now = millis();
+  if (now < w1_power_until)
+    return;
+#endif
+  if (uptime & 1
+#ifdef W1_PARASITE_POWER
+      // if more than 1 sensor and only parasite power: convert every cycle
+      || ds18x20_sensors >= 2
+#endif
+  ) {
     // 2mS
     Ds18x20Convert();          // Start conversion, takes up to one second
   } else {