Add support for Parasitic Power mode, including secondary GPIO control of external "strong pull-up" circuit.

README.md

@@ -6,11 +6,13 @@
 
 ## Introduction
 
-This is an example application for the Maxim Integrated DS18B20 Programmable Resolution 1-Wire Digital Thermometer device.
+This is an example application for the Maxim Integrated DS18B20 Programmable Resolution 1-Wire Digital Thermometer 
+device.
 
 It supports a single or multiple devices on the same 1-Wire bus.
 
-It is written and tested for v3.3 of the [ESP-IDF](https://github.com/espressif/esp-idf) environment, using the xtensa-esp32-elf toolchain (gcc version 5.2.0, crosstool-ng-1.22.0-80-g6c4433a).
+It is written and tested for v3.3 and v4.1-beta1 of the [ESP-IDF](https://github.com/espressif/esp-idf) environment,
+using the xtensa-esp32-elf toolchain (gcc version 5.2.0, crosstool-ng-1.22.0-80-g6c4433a).
 
 Ensure that submodules are cloned:
 
@@ -23,7 +25,8 @@ Build the application with:
     $ idf.py build
     $ idf.py -p (PORT) flash monitor
 
-The program should detect your connected devices and periodically obtain temperature readings from them, displaying them on the console.
+The program should detect your connected devices and periodically obtain temperature readings from them, displaying them
+on the console.
 
 ## Dependencies
 
@@ -34,17 +37,27 @@ This application makes use of the following components (included as submodules):
 
 ## Hardware
 
-To run this example, connect one or more DS18B20 devices to a single GPIO on the ESP32. Use the recommended pull-up resistor of 4.7 KOhms, connected to the 3.3V supply.
+To run this example, connect one or more DS18B20 devices to a single GPIO on the ESP32. Use the recommended pull-up 
+resistor of 4.7 KOhms, connected to the 3.3V supply.
 
 `idf.py menuconfig` can be used to set the 1-Wire GPIO.
 
-If you have several devices and see occasional CRC errors, consider using a 2.2 kOhm pull-up resistor instead. Also consider adding decoupling capacitors between the sensor supply voltage and ground, as close to each sensor as possible.
+If you have several devices and see occasional CRC errors, consider using a 2.2 kOhm pull-up resistor instead. Also 
+consider adding decoupling capacitors between the sensor supply voltage and ground, as close to each sensor as possible.
+
+If you wish to enable a second GPIO to control an external strong pull-up circuit for parasitic power mode, ensure 
+`CONFIG_ENABLE_STRONG_PULLUP=y` and `CONFIG_STRONG_PULLUP_GPIO` is set appropriately.
+ 
+See documentation for [esp32-ds18b20](https://www.github.com/DavidAntliff/esp32-ds18b20-example#parasitic-power-mode)
+for further information about parasitic power mode, including strong pull-up configuration.
+
 
 ## Features
 
 This example provides:
 
- * External power supply mode.
+ * External power supply detection.
+ * Parasitic power supply detection.
  * Static (stack-based) or dynamic (malloc-based) memory model examples.
  * No global variables.
  * Device search.

components/esp32-ds18b20

@@ -1 +1 @@
-Subproject commit ae81f86e0ee1cd65b6d6a2ad59deb7ba295ab3c4
+Subproject commit e763961d445263cdfc93d0fe516f917ba95a43e1

components/esp32-owb

@@ -1 +1 @@
-Subproject commit af25dd31dbb1e80364b99fad29815badfab0ceda
+Subproject commit c678bad2af657359ebdab90473df2f65ff5ac83d

main/Kconfig.projbuild

@@ -2,13 +2,45 @@ menu "esp32-ds18b20-example Configuration"
 
 config ONE_WIRE_GPIO
     int "OneWire GPIO number"
-	range 0 34
-	default 5
+	range 0 33
+	default 4
 	help
 		GPIO number (IOxx) to access One Wire Bus.
 
 		Some GPIOs are used for other purposes (flash connections, etc.) and cannot be used.
 
-		GPIOs 35-39 are input-only so cannot be used to drive the One Wire Bus.
+		GPIOs 34-39 are input-only so cannot be used to drive the One Wire Bus.
+
+config ENABLE_STRONG_PULLUP_GPIO
+    bool "Enable strong pull-up controlled by GPIO (MOSFET)"
+    default n
+    help
+        An external circuit can be used to provide a strong pull-up to the One Wire Bus.
+        This is useful when the bus has parasitic-powered devices and extra current is
+        required to power them, such as during temperature ADC conversions.
+
+        An example of such a circuit for the ESP32 is a P-channel MOSFET (such as the BS250)
+        connected Source-to-Drain between a current-limiting resistor (e.g. 270ohm for 12mA
+        max at 3.3V), itself connected to VCC, and the One Wire Bus data line. The Gate is
+        connected to the GPIO specified here.
+
+config STRONG_PULLUP_GPIO
+    int "Strong pull-up GPIO number"
+    range 0 33
+    default 5
+    help
+		GPIO number (IOxx) to control the strong pull-up on the One Wire Bus, perhaps
+		via a P-channel MOSFET between VCC and the One Wire Bus data line.
+
+		This GPIO will be set as an output and driven high during temperature conversion.
+		This would enable the MOSFET providing current to the devices.
+
+		At all other times it will be driven low, switching off the MOSFET and allowing
+		the One Wire Bus to operate normally.
+
+		Some GPIOs are used for other purposes (flash connections, etc.) and cannot be used.
+
+		GPIOs 34-39 are input-only so cannot be used to drive the One Wire Bus.
+    depends on ENABLE_STRONG_PULLUP_GPIO
 
 endmenu

main/app_main.c

@@ -40,7 +40,6 @@ _Noreturn void app_main()
 {
     // Override global log level
     esp_log_level_set("*", ESP_LOG_INFO);
-    esp_log_level_set("*", ESP_LOG_DEBUG);
 
     // To debug, use 'make menuconfig' to set default Log level to DEBUG, then uncomment:
     //esp_log_level_set("owb", ESP_LOG_DEBUG);
@@ -149,14 +148,23 @@ _Noreturn void app_main()
 //        vTaskDelay(1000 / portTICK_PERIOD_MS);
 //    }
 
-    // Check for parasitic-powered devices that require a strong-pullup
-    bool require_strong_pullup = false;
-    ds18b20_check_for_parasite_power(owb, &require_strong_pullup);
-    printf("Strong pullup (parasitic power) %srequired\n", require_strong_pullup ? "" : "not ");
-    if (require_strong_pullup)
-    {
+    // Check for parasitic-powered devices
+    bool parasitic_power = false;
+    ds18b20_check_for_parasite_power(owb, &parasitic_power);
+    if (parasitic_power) {
+        printf("Parasitic-powered devices detected");
     }
 
+    // In parasitic-power mode, devices cannot indicate when conversions are complete,
+    // so waiting for a temperature conversion must be done by waiting a prescribed duration
+    owb_use_parasitic_power(owb, parasitic_power);
+
+#ifdef CONFIG_ENABLE_STRONG_PULLUP_GPIO
+    // An external pull-up circuit is used to supply extra current to OneWireBus devices
+    // during temperature conversions.
+    owb_use_strong_pullup_gpio(owb, CONFIG_STRONG_PULLUP_GPIO);
+#endif
+
     // Read temperatures more efficiently by starting conversions on all devices at the same time
     int errors_count[MAX_DEVICES] = {0};
     int sample_count = 0;
@@ -164,21 +172,15 @@ _Noreturn void app_main()
     {
         TickType_t last_wake_time = xTaskGetTickCount();
 
-        while (1) {
+        while (1)
+        {
             last_wake_time = xTaskGetTickCount();
 
             ds18b20_convert_all(owb);
 
             // In this application all devices use the same resolution,
             // so use the first device to determine the delay
-            if (require_strong_pullup) {
-                ets_delay_us(750000);
-                gpio_set_level(5, 0);
-            }
-            else
-            {
             ds18b20_wait_for_conversion(devices[0]);
-            }
 
             // Read the results immediately after conversion otherwise it may fail
             // (using printf before reading may take too long)

sdkconfig.defaults

@@ -0,0 +1,4 @@
+#
+# Log output
+#
+CONFIG_LOG_DEFAULT_LEVEL=4