Adafruit USB + Serial RGB Backlight Character LCD Backpack VBScript API

System Requirements:

  • Adafruit USB Serial RGB Backlight Character LCD Backpack

The Problem:

I recently needed a fast, cheap and modular way to output small amounts of information from a headless Windows 7 appliance, something that didn’t require a large amount of electrical engineering work or assembly while at the same time working over USB.

I accidentally stumbled upon a product by Adafruit, who seem to be tightly aligned with the Raspberry Pi/Arduino, however USB is USB which means that making it cooperate with Win32 wouldn’t be particularly challenging.

Being the lazy person that I am, I never much care for the idea of having to repeatedly type out control commands through a command line parser to get what I want and quite frankly, getting a NT Command Prompt to reliably pass anything out to a Serial Port is more or less a futile exercise unless you are using Plink or replace the shell entirely with something more robust.

My solution was quite simple, create a O-O VBScript API for running it via CScript that can in turn be called from the NT command line where required.

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More Info

This API does what I require it to do. I have implemented all of the main command syntax from the Adafruit documentation (links below). It is classful and self contained. As long as you can create a FileSystemObject and can find the COM Port, you can make use of it.

[Update 25/04/2019] You can now obtain this code directly from Github.

View: AdafruitUsbSerial on GitHub

' AdafruitUsbSerial Application Programming Interface v1.0.4

' © C:Amie | 1996 - 2014

' Not for commercial reproduction without the express permission of the author

' No warranty is offered or implied as a result of downloading or using this APIClass AdafruitUsbSerialprivate m_ForReadingprivate m_SCREEN_OFF

private m_SCREEN_ON

private m_AUTO_SCROLL_ON


private m_CLEAR_SCREEN








private m_SET_BLINK_ON

private m_SET_BLINK_OFF

private m_SET_RGB

private m_SET_CONTRAST

private m_SET_BRIGHTNESSprivate m_iPortNumber

private m_byteCharacterLength

private m_bolDebug

private m_bolAutoScroll

private m_bolUnderlineCursor

private m_bolBlinkCursorprivate m_fso private

sub Class_Initialize
m_ForReading = 1
m_SCREEN_OFF = chr(254) & chr(70)
m_SCREEN_ON = chr(254) & chr(66)
m_AUTO_SCROLL_ON = chr(254) & chr(81)
m_AUTO_SCROLL_OFF = chr(254) & chr(82)
m_CLEAR_SCREEN = chr(254) & chr(88)
m_SET_STARTUP_SPLASH = chr(254) & chr(64)
m_SET_CURSOR_POSITION = chr(254) & chr(71)
m_SET_CURSOR_HOME = chr(254) & chr(72)
m_SET_CURSOR_BACK = chr(254) & chr(76)
m_SET_CURSOR_FORWARD = chr(254) & chr(77)
m_SET_UNDERLINE_ON = chr(254) & chr(74)
m_SET_UNDERLINE_OFF = chr(254) & chr(75)
m_SET_BLINK_ON = chr(254) & chr(83)
m_SET_BLINK_OFF = chr(254) & chr(84)
m_SET_RGB = chr(254) & chr(208)
m_SET_CONTRAST = chr(254) & chr(80)
m_SET_BRIGHTNESS = chr(254) & chr(153)

m_iPortNumber = 1
m_byteCharacterLength = 32
m_bolDebug = false
m_bolAutoScroll = true
m_bolUnderlineCursor = false
m_bolBlinkCursor = false

set m_fso = CreateObject("Scripting.FileSystemObject")
end sub

private sub Class_Terminate
set m_fso = nothing
end sub

public property get PortNumber
PortNumber = m_iPortNumber
end property

public property let PortNumber(ByRef iIn)
m_iPortNumber = iIn
end property

public property get CharacterLength
CharacterLength = m_byteCharacterLength
end property

public property let CharacterLength(ByRef byteIn)
m_byteCharacterLength = byteIn
end property

public property get Debug()
Debug = m_bolDebug
end property

public property let Debug(ByRef bolIn)
m_bolDebug = bolIn
end property

public property get AutoScroll()
AutoScroll = m_bolAutoScroll
end property

public property let AutoScroll(ByRef bolIn)
if (bolIn) then
end if
m_bolAutoScroll = bolIn
end property

public property get Underline()
Underline = m_bolUnderlineCursor
end property

public property let Underline(ByRef bolIn)
if (bolIn) then
end if
m_bolUnderlineCursor = bolIn
end property

public property get Blink()
Blink = m_bolBlinkCursor
end property

public property let Blink(ByRef bolIn)
if (bolIn) then
end if
m_bolBlinkCursor = bolIn
end property

public sub clearScreen()
end sub public sub screenOn()
end sub

public sub screenOff()
end sub

public sub changeSplashScreen(ByVal strIn)
strIn = Left(strIn, m_byteCharacters)
' Force it to be exactly 32 characters by padding
do while (Len(strIn) < m_byteCharacters)
strIn = (strIn & " ")
end sub

public sub backlight(ByRef byteR, ByRef byteG, ByRef byteB)
end sub

' Valid Range 0 - 255. Values between 180 and 220 are suggested
public sub contrast(ByRef byteIn)
end sub

' Valid Range 0 - 255.
public sub brightness(ByRef byteIn)
end sub

public sub setCursorPosition(ByRef iX, ByRef iY)
end sub

public sub home()
end sub

public sub back()
end sub

public sub goBack(ByRef iIn)
Dim i
for i = 1 to iIn
end sub

public sub forward()
end sub

public sub goForward(ByRef iIn)
Dim i
for i = 1 to iIn
end sub

public sub delete()
me.write(" ")
end sub

public sub write(ByRef strIn)
Dim serialWriter
if (me.Debug) then
wscript.echo strIn
end if
set serialWriter = m_fso.CreateTextFile("COM" & m_iPortNumber & ":",True)
set serialWriter = nothing
end sub

public sub teletype(ByRef strIn, ByRef iDelayMs)
Dim i
Dim iLen
iLen = Len(strIn)
for i = 1 to iLen
me.write(Mid(strIn, i, 1))
end sub

public function testComPort(ByRef byteNumber)
Dim serialWriter
if (me.Debug) then
wscript.echo "Attempting communications with COM" & byteNumber
end if
On Error Resume Next
set serialWriter = m_fso.CreateTextFile("COM" & byteNumber & ":",True)
set serialWriter = nothing
if (err.number = 0) then
testComPort = true
testComPort = false
end if
On Error Goto 0
end function

End Class

Copy it into your VBScript project file or into a dedicated class file and include it. Once it is in scope, the example below shows a general usage pattern for the main API.

It is recommended that all projects include and set the first 8 lines shown below, just so that you can ensure that you are tuning your project in the way that you want it. The remainder of the code shows examples of how to use the functions.

As a result of the USB driver allocating COM ports in a fairly dynamic way under Win32, you cannot expect to hard code your COM Port inside the project – particularly if the physical USB port that the backpack is connected to changes. Consequently, you can use testComPort() to attempt to locate the correct port as shown below. The function will terminate on the first port that it finds with an active serial output line available, if you have multiple active serial ports available on your project, the function may find the wrong port.

Finally, Adafruit recommends – at a minimum -adding a 10 millisecond delay between each command, which is not shown below. You should use WScript.Sleep(10) to achieve similar under VBScript. If you don’t, everything shown below with the exception of the executing of the Teletype macro will occur in well under a second.

Dim usbSerial

set usbSerial = new AdafruitUsbSerial

    usbSerial.PortNumber = 3              ' Set to COM3

    usbSerial.Debug = true                ' Inputs will be written back to WScript

    usbSerial.CharacterLength = 32        ' 32 is the default

    usbSerial.AutoScroll = true           ' Enable/Disable Auto Scroll

    usbSerial.Underline = true            ' Enable Cursor Underline

    usbSerial.Blink = true                ' Enable Cursor Blink' Find the first live COM Port if you don't know where it is

Dim iComPort

for iComPort = 1 to 30

    if (usbSerial.testComPort(iComPort)) then

        usbSerial.PortNumber = iComPort

        Exit For

    end if

next' Write Text

usbSerial.write("some text")' Write on both lines

usbSerial.write("line one" & vblf & "line two")' Clear the screen

usbSerial.clearScreen()' Screen Off


' Screen On

' Change the Backlight Colour
call usbSerial.backlight(255, 0, 255) ' Sets the RGB values (Fuchsia in this case)

' Set the screen brightness
usbSerial.brightness(180) ' 0 - 255

' Set the screen contrast
usbSerial.contrast(180) ' 0 - 255

' Set the Cursor Position
usbSerial.home()                  ' Moves to character 1, row 1
usbSerial.back()                  ' Moves the cursor back 1 character
usbSerial.forward()               ' Moves the cursor forward 1 character
usbSerial.goBack(5)               ' Steps the cursor back 5 characters
usbSerial.goForward(6)            ' Progresses the cursor forward 6 characters
usbSerial.setCursorPosition(5,1)  ' Sets the cursor to Character 5 on Row 1
usbSerial.delete()                ' Moves the cursor back 1 and clears the previous character

' Teletype (Macro)
call usbSerial.teletype("this will teletype out", 100) ' Write the text, with a 0.1 second character delay

' Change the Adafruit Splash Screen (Auto truncated/padded to usbSerial.CharacterLength)
usbSerial.changeSplashScreen("This is a splash screen message")

' Clean up and free resources
set usbSerial = nothing

Thanks to a structured API it is as easy as that!

View: Adafruit: Command Reference
View: Adafruit: Sending Text

See Also

View: Adafruit

Buy Adafruit USB Serial RGB Backlight Character LCD Backpack, and other Adafruit components from Amazon & help support this site: