B4R Tutorial Controlling an RGB Led from the PC

This example is based on the connection diagram described here: https://www.b4x.com/android/forum/threads/rgb-leds.65998/

In this case we will control the led color with a B4J program.

The B4J program is based on serial connector: https://www.b4x.com/android/forum/threads/tool-external-serial-connector.65724/

When you use the serial connector you need to run the program from the IDE and the click on the Disconnect button in the logs tab to release the serial port. You can then connect to the serial port from the serial connector.
When you want to make an update to the program you need to disconnect the serial connector (close button).


The B4J program will send the color value to the Arduino which will then update the led.

B4R code:
Sub Process_Globals
   Public Serial1 As Serial
   Private rpin, gpin, bpin As Pin
   Private const COMMON_ANODE As Boolean = False
   Private astream As AsyncStreams
   Private bc As ByteConverter
End Sub

Private Sub AppStart
   astream.Initialize(Serial1.Stream, "astream_NewData", "astream_Error")
   astream.WaitForMoreDataDelay = 5
   rpin.Initialize(3, rpin.MODE_OUTPUT)
   gpin.Initialize(5, rpin.MODE_OUTPUT)
   bpin.Initialize(6, rpin.MODE_OUTPUT)
End Sub

Sub Astream_NewData (buffer() As Byte)
   Log("Received: ", bc.HexFromBytes(buffer), ", len: ", buffer.Length)
   For i = 0 To buffer.Length - 4 Step 4
       'common is +
       rpin.AnalogWrite(255 - buffer(i + 1))
       gpin.AnalogWrite(255 - buffer(i + 2))
       bpin.AnalogWrite(255 - buffer(i + 3))
       rpin.AnalogWrite(buffer(i + 1))
       gpin.AnalogWrite(buffer(i + 2))
       bpin.AnalogWrite(buffer(i + 3))
     End If
End Sub

Sub Astream_Error
End Sub

This line is very important:
For i = 0 To buffer.Length - 4 Step 4
Messages can arrive together. This will happen when you quickly change the color in the custom colors dialog.

This 'for loop' will:
1. Handle all the arrived messages.
2. Ignore partial messages.

Setting the saturation and brightness to 100% yields good results. The led color matches the selected color.

Note: There is a bug in B4R 1.00 beta #6. It will cause additional random bytes to be added to the messages. It is fixed for the next beta.


  • B4J_ColorPicker.zip
    4 KB · Views: 469


Licensed User
I am trying to implement its' bluetooth controlled by phone version but couldnt even set up the hm10 since you are using a shield mine is different. ( I know they are based on same hm10 but cant make the connections right i think ) . Would be nice to see a bluetooth example =)