documented how to use SSL encryption for MQTT

homieiot · Mar 24, 2019 · ebac43a · ebac43a
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diff --git a/docs/advanced-usage/compiler-flags.md b/docs/advanced-usage/compiler-flags.md
@@ -1,4 +1,8 @@
-Compiler flags can be used to remove certain functionality from homie-esp8266. This can become useful if your firmware gets too large in size and is not upgradable any more over OTA. On the other hand these compiler flags allow to remove features from homie-esp8266, that you do not require or do not use.
+Compiler flags can be used to add or remove certain functionality from homie-esp8266.
+
+Removing functionality can become useful if your firmware gets too large in size and is not upgradable any more over OTA. On the other hand these compiler flags allow to remove features from homie-esp8266, that you do not require or do not use.
+
+Adding functionality or features is useful to enable only partly implemented features or unstable or experimental features.
 
 **HOMIE_CONFIG**
 
@@ -20,4 +24,14 @@ build_flags = -D HOMIE_MDNS=0
 
 This reduces the firmware size by about 6400 bytes.
 
+**ASYNC_TCP_SSL_ENABLED**
+
+This compiler flag allows to use SSL encryption for MQTT connections. All other network connections still can not be encrypted like HTTP or OTA.
+
+```
+build_flags =
+  -D ASYNC_TCP_SSL_ENABLED=1
+  -D PIO_FRAMEWORK_ARDUINO_LWIP2_HIGHER_BANDWIDTH
+```
 
+The additional flag `PIO_FRAMEWORK_ARDUINO_LWIP2_HIGHER_BANDWITH` is necessary for SSL encryptions to work properly.
diff --git a/docs/others/limitations-and-known-issues.md b/docs/others/limitations-and-known-issues.md
@@ -1,6 +1,6 @@
 # SSL support
 
-In Homie for ESP8266 v1.x, SSL was possible but it was not reliable. Due to the asynchronous nature of the v2.x, SSL is not available anymore.
+In Homie for ESP8266 v1.x, SSL was possible but it was not reliable. Due to the asynchronous nature of the v2.x, SSL is not completely available anymore. Only MQTT connections can be encrypted with SSL.
 
 # ADC readings