update readme.md

README.md

@@ -28,6 +28,26 @@ ESP32 is supported since 0.2.0 see https://github.com/RobTillaart/TM1637_RT/pull
 - https://docs.wokwi.com/parts/wokwi-tm1637-7segment#simulator-examples
 
 
+#### Hardware connection and performance
+
+From tests of SteveMicroCode (See #29) it became clear that the proposed hardware in the
+datasheet is very robust but slow. See page 8 datasheet.
+Leaving out the 100 pF capacitors on the CLK and DIO line, or dimension them smaller,
+allows for faster communication and thus more efficient CPU use. 
+
+Additional tests of wfdudley (See Keyboard Scanner section) shows that reducing
+the pull up resistor from 10 KΩ to 1000 Ω improves the signal quality.
+This too allows for faster communication and efficient CPU use.
+
+Datasheet page 3: _and the clock frequency should be less than 250K_ (KHz)   
+This implies that the **setBitDelay()** could be set much lower than the default 10 micro
+seconds of the library. On "slower" platforms it might even be 0.
+However it is always important to do your own tests if you want to tweak performance
+beyond the specifications of the datasheet. 
+Interference from other electronic components is often nearby, and if you need longer
+cables consider shielded ones.
+
+Note: Ω = ALT-234
 
 
 ## Interface
@@ -84,6 +104,10 @@ Applications include:
   - meters + centimetre MM:CC  (e.g distance sensor)
   - feet + inches FF:II
   - any pair of integers (-9 .. 99) side by side.
+
+
+#### Display functions III
+
 - **void displayCelsius(int temp, bool colon = false)** print temperature in **Celsius** format.
 The function allows a range from -9 .. 99 + °C.
 The colon is default false.
@@ -99,16 +123,19 @@ Colon can be used e.g. to indicate under- or overflow, or any other threshold.
 TM.displayCelsius(temperature, (temperature < -9) || (temperature > 99));
 ```
 
-##### Notes on temperature
+Note that the effective range of Celsius and Fahrenheit differs.
+When Fahrenheit goes from -9 to 99 Celsius goes from -26 to 37 (etc).
 
-Note that the effective range of C and F differs
-|   F   |   C   |   F   |   C   |
-|:-----:|:-----:|:-----:|:-----:|
-|  -9   | -26   |   16  |  -9   |
-|  99   |  37   |  210  |  99   |
+|   F   |   C   |      |   F   |   C   |
+|:-----:|:-----:|:----:|:-----:|:-----:|
+|  -9   | -26   |      |   16  |  -9   |
+|  99   |  37   |      |  210  |  99   |
 
-Need to think about a 3 digit temperature to extend the range -99 .. 999
-or to have one decimal.
+A three digit temperature, e.g. range -99 .. 999, would be possible but one has 
+to leave out either the ° character or the C/F.
+As the C/F is more informative, the choice is fairly easy.
+Question is how to API should change, new function of new behaviour?
+See future.
 
 
 #### Brightness
@@ -209,11 +236,11 @@ when the library is used with an ESP32. The function called there **nanoDelay(n)
 needs manual adjustment depending upon processor frequency and time needed for a digitalWrite.
 Feel free to file an issue to get your processor supported.
 
+----
 
 ## Keyboard Scanner usage and notes
 
 - Kudos to wfdudley for this section - See #11
-- 
 
 Calling **keyscan()** returns a uint8_t, whose value is 0xff if no keys are being pressed at the time.  
 The TM1637 can only see one key press at a time, and there is no "rollover".  
@@ -328,7 +355,7 @@ See examples
 
 - testing other platforms.
 - refactor readme.md
-- remove degree sign from **displayCelsius()** ?
+- remove degree sign from **displayCelsius()**
   - would allow one extra digit.
   - **displayFahrenheit()** idem.
   - could be optional when needed e.g. below -9 or above 99