Use send_now to ensure faster communication via Serial (#13)

* Use send_now to trigger faster communication through serial.

* Use python 3.9 in anticipation

.travis.yml

@@ -1,6 +1,6 @@
 language: python
 python:
-- '3.7'
+- '3.9'
 sudo: false
 cache:
   directories:

CHANGELOG.md

@@ -1,3 +1,7 @@
+### 0.0.18
+
+* Use send_now to trigger a communication event once a command has been processed.
+
 ### 0.0.17
 
 * Add the ability to do SPI byte reads

src/commandrouting.cpp

@@ -274,5 +274,12 @@ int CommandRouter::processSerialStream() {
     Serial.print(buffer);
   }
   Serial.print("\n");
+
+  // Call send_now on success to ensure that the response is immediate
+  // Otherwise, the serial buffer will wait for up to 5 ms
+  // for the buffer to get full (it never will) before sending any data
+  // https://www.pjrc.com/teensy/td_serial.html
+  Serial.send_now();
+
   return result;
 }