BCD to Decimal conversion and vice versa

[Alhashemi]

Hi everyone,

I need some help in converting BCD to Decimal using Visual Basic 6. I searched the internet for weeks now and couldn't find a code which would convert BCD to Decimal and vice versa. I need it because I need to convert the values of the frequencies after being read by FSUIPC (They are read in BCD) to decimal and then add or subtract according to a specific reading from the parallel port. Anyhow, Visual Basic 6 gives me the decimal representation of the BCD value and I found this article: http://electronicdesign.com/Article/Artfeed=Top20

where it states that the following equation or formula : dbcd = (m*9256 + I*516 + b*26 + cc)*6 + x

can be used to convert decimal to BCD. It gives the right answer up to 45. After 46, things start going wrong so in small words. It is not reliable enough.

Long story short, I wrote a pretty long code to do the conversion and it works nicely yet it is complicated and difficult to amend. So could any one help me?? is there a VB code such as the dec2bcd code in C++? or is there any equation that would perfectly work?

I appreciate your kind help and looking forward to hearing from you...anyone..

Thanks and buy

N.B: The long code is as follows, if anyone is interested

Option Explicit

'This program is for controlling COM1 Radio with two keys in the keyboard (Alt & Ctrl)

Private Sub Form_Load()

Dim dwResult As Long

Dim Comm1_Radio As Long

'Set COM1 Radio to 118.00Mhz using BCD of 1800 which is 6144 to set the Radio

'frequency as the last digit (1) is considered to be there already

Comm1_Radio = 6144

'Send frequency to Radio @ MSFS

Call FSUIPC_Write(&H311A, 2, VarPtr(Comm1_Radio), dwResult)

Call FSUIPC_Process(dwResult)

End Sub

Private Sub butOK_Click()

Unload frmMain

End Sub

Private Sub Form_Unload(Cancel As Integer)

FSUIPC_Close

End Sub

Private Sub Timer1_Timer()

Dim dwResult As Long

Dim Comm1_Radio As Long

Dim Modified_Radio As Long

'The 4 Values required at conversion

Dim val() As Long

ReDim val(4)

'Titles of the 4 Values, val(1), val(2), val(3) and val(4)

Dim i As Long

'Required integer (n) for the conversion in sequence

Dim n As Long

'Read the frequency and recorded as Comm1_Radio (BCD). To control it, we need to change it to Bin -> Dec (Each 4 bits)

'-> Change it -> Binary (Each digit) -> BCD again -> Send it to MSFS

If FSUIPC_Read(&H311A, 2, VarPtr(Comm1_Radio), dwResult) Then

If FSUIPC_Process(dwResult) Then

'Present Comm1_Radio in the following format

lblComm1_Radio.Caption = Format(Comm1_Radio, "0")

Else 'No reading

lblComm1_Radio.Caption = "Processing: " & ResultText(dwResult)

End If

Else 'No reading

lblComm1_Radio.Caption = "Reading: " & ResultText(dwResult)

End If

'Convert the value Comm1_Radio to Binary

lblbinary.Caption = DecimalToBinary(Comm1_Radio)

'Add either 2 or 3 0's to make the total 16 bit

If Len(lblbinary.Caption) = 13 Then

lblbinary.Caption = "000" & lblbinary.Caption

ElseIf Len(lblbinary.Caption) = 14 Then

lblbinary.Caption = "00" & lblbinary.Caption

End If

'Bits: 1, 5, 9 and 13

For n = 1 To 16 Step 4

'Take the following 3 bits after each of the bits mentioned above

lbldecimal.Caption = Mid(lblbinary.Caption, n, 4)

i = i + 1

'Change each of the values to Decimal

val(i) = BinaryToDecimal(lbldecimal.Caption)

Next n

'Put the 4 values togather as a number = the frequency in Decimal

lbldecimal1.Caption = val(1) & val(2) & val(3) & val(4)

'Check the input

Label8.Caption = Inp(&H60)

'Speed the change if the user keeps the same input

'Case 1 input(Increase COMM1 Standby Frequency)*******************************************************************

If Label8.Caption = 29 Then

Timer1.Interval = Timer1.Interval - 1

If Timer1.Interval < 1 Then

Timer1.Interval = 1

End If

'Icrease the lately converted value of COMM1 frequency by 2.5 kHz (Decimal)

lblModified_Radio.Caption = lblModified_Radio.Caption + 2.5

ElseIf Label8.Caption = 56 Then

Timer1.Interval = Timer1.Interval - 1

If Timer1.Interval < 1 Then

Timer1.Interval = 1

End If

lblModified_Radio.Caption = lblModified_Radio.Caption - 2.5

Else

Timer1.Interval = 50

End If

'Get red of the decimal point without rounding

Label9.Caption = CSng(lblModified_Radio.Caption)

'Convert each digit in the latest value to binary

For n = 1 To 4

Label11.Caption = Mid(Label9.Caption, n, 1)

If Label11.Caption = 0 Then

Label12(n - 1) = "0000"

Else

val(n) = DecimalToBinary(Label11.Caption)

Label12(n - 1).Caption = val(n)

If Len(Label12(n - 1).Caption) = 1 Then

Label12(n - 1).Caption = "000" & val(n)

ElseIf Len(Label12(n - 1).Caption) = 2 Then

Label12(n - 1).Caption = "00" & val(n)

ElseIf Len(Label12(n - 1).Caption) = 3 Then

Label12(n - 1).Caption = "0" & val(n)

End If

End If

Next n

'Record the Finally coverted value as one large binary value

Label10.Caption = Label12(0).Caption & Label12(1).Caption & Label12(2).Caption & Label12(3).Caption

'Convert that value to decimal to derive the BCD of the new frequency

Label14.Caption = BinaryToDecimal(Label10.Caption)

Comm1_Radio = Label14.Caption

'Send the new frequency to MSFS

Call FSUIPC_Write(&H311A, 2, VarPtr(Comm1_Radio), dwResult)

Call FSUIPC_Process(dwResult)

End Sub

'Converting Decimal to Binary

Public Function DecimalToBinary(ByVal pValue As Long) As String

Dim C As Byte

Dim SubValue As Long

Dim Value As String

On Error GoTo ErrorHandler

SubValue = (2 ^ 31) - 1

While SubValue > 0

If pValue - SubValue >= 0 Then

pValue = pValue - SubValue

Value = Value & "1"

Else

If val(Value) > 0 Then Value = Value & "0"

End If

SubValue = SubValue / 2

Wend

DecimalToBinary = Value

Exit Function

ErrorHandler:

DecimalToBinary = "0"

End Function

'Converting Binary to Decimal

Public Function BinaryToDecimal(ByVal pValue As String) As Long

Dim C As Integer

Dim PosValue As Long

Dim Value As Long

On Error GoTo ErrorHandler

PosValue = 1

For C = Len(pValue) To 1 Step -1

If Mid(pValue, C, 1) = "1" Then Value = Value + PosValue

PosValue = PosValue * 2

Next

BinaryToDecimal = Value

Exit Function

ErrorHandler:

BinaryToDecimal = 0

End Function

[Pete Dowson]

I need some help in converting BCD to Decimal using Visual Basic 6.

BCD is merely the use a a few bits in binary for each digit, so all you have to do is separate the bits.

For example, the frequency 123.45 is represented in BCD as hexadecimal 0x2345, probably $2345 in Basic. Right? Of those 4 digits, the lowest, the 5, is in the lowest 4 bits. the next is in the next 4 bits and so on. It is almost ALREADY in character format, you just need to split the bits up. There's no clever computation ever needed!

All you need are SHIFTS, logical AND, and OR.

I don't know VB so I'll show it in ordinary 'English':

Take $2345

First store the character '1', as this is assumed first. Result so far = "1".

Take the $2345, SHIFT it right by 12 bits. Result is 2.

OR the character '0' with it. This gives character '2'. Store it in the reslut which is now "12".

Take the $2345 again, SHIFT it right by 8 bits, then AND it with 15 ($000F). Result is 3.

OR the character '0' with it. This gives character '3'. Store it in the reslut which is now "123".

Add the decimal '.' here to give "123."

Take the $2345 again, SHIFT it right by 4 bits, then AND it with 15 ($000F). Result is 4.

OR the character '0' with it. This gives character '4'. Store it in the reslut which is now "123.4"

Take the $2345 again, AND it with 15 ($000F). Result is 5.

OR the character '0' with it. This gives character '5'. Store it in the reslut which is now "123.45"

Okay?

Another way is to simply print it in hexadecimal, if your VB library "print" functions support this. You'll immediately get the string "2345" which you can massage into "123.45" quite easily.

Pete

[Graham Pollitt]

To convert the value read from FS to a decimal format I use this in VB2005 and VB2008

First set up offset holder and process the read request

Dim RNav2Freq As Offset(Of Short) = New FSUIPC.Offset(Of Short)("aircraft radios", &H352)

Dim Nav2Freq As Decimal

FSUIPCConnection.Process("aircraft radios")

Nav2Freq = RNav2Freq.Value 'freq tuned into nav2 offset

'get the BCD of the value read and add 10000 to get the 1 ie 1025 * 10000 = 11025

Nav2Freq = Val(Str(Hex(nav2freq))) + 10000

Not sure of re-converting as I have never used it.

Graham

[HarryL]

Dear Alhashemi

another simple way to convert BCD into a Decimal is the following (I did it in c#, but should be similar in VB):

1: write the BCD value into a string with the format option "X4"

2: by string operations add a "1" in front of this string

3: take the value of this string and devide it by 100

private double bcd2dbl(int bcd)

{

string bcdstr = "1" + (bcd).ToString("X4");

int bcdint = Convert.ToInt32(bcdstr);

double freq = (double)bcdint / 100;

return freq;

}

Harald