From 580600aa538fe391d7f7d9be683bc7d82234d47b Mon Sep 17 00:00:00 2001
From: David Antliff <david@pitchblende.co.nz>
Date: Tue, 5 Sep 2017 11:31:39 +1200
Subject: [PATCH] Updated README.

---
 README.md            |  2 ++
 components/esp32-owb |  2 +-
 main/app_main.c      | 11 ++++++++++-
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 0061da9..b136eac 100644
--- a/README.md
+++ b/README.md
@@ -33,6 +33,8 @@ To run this example, connect one or more DS18B20 devices to a single GPIO on the
 
 `make 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.
+
 ## Features
 
 This example provides:
diff --git a/components/esp32-owb b/components/esp32-owb
index 57bcaf0..c62cd2e 160000
--- a/components/esp32-owb
+++ b/components/esp32-owb
@@ -1 +1 @@
-Subproject commit 57bcaf06f500953e3acb97d23c6a6a98712824ab
+Subproject commit c62cd2e7fe0850b29e2563d1fde49ff452676b57
diff --git a/main/app_main.c b/main/app_main.c
index 95224bc..d9a875c 100644
--- a/main/app_main.c
+++ b/main/app_main.c
@@ -44,6 +44,9 @@ void app_main()
 {
     esp_log_level_set("*", ESP_LOG_INFO);
 
+    /// stable readings require a brief period before communication
+    vTaskDelay(1000.0 / portTICK_PERIOD_MS);
+
     // Create a 1-Wire bus
 #ifdef USE_STATIC
     OneWireBus owb_static;        // static allocation
@@ -132,6 +135,7 @@ void app_main()
 //    }
 
     // read temperatures more efficiently by starting conversions on all devices at the same time
+    int crc_errors[MAX_DEVICES] = {0};
     if (num_devices > 0)
     {
         while (1)
@@ -156,7 +160,12 @@ void app_main()
             printf("\nTemperature readings (degrees C):\n");
             for (int i = 0; i < num_devices; ++i)
             {
-                printf("  %d: %.1f\n", i, temps[i]);
+                if (temps[i] == DS18B20_INVALID_READING)
+                {
+                    ++crc_errors[i];
+                }
+
+                printf("  %d: %.1f    %d errors\n", i, temps[i], crc_errors[i]);
             }
 
             // make up delay to approximately 1 second per measurement