B4J Question Negative value from HEX

[Declan]

I am working with a GPS device that sends both Lat and Lon in HEX format.
I must "extract" the negative value from the received HEX strings.
Example:

Latitude = 10D27FBC (HEX)
= 282230716
Actual Latitude is 28.2230716
This is correct as it is a positive value.

Longitude = F0B00A5E (HEX)
= 4038068830
This should be -25.6898466

How do I determine whether the HEX value is negative - then convert the decimal value?

 

[teddybear]

The first bit is the sign bit, that is, the first hex number is 8-F, the value is a negative, the number = number - 2^32.
it should be 4038068830-4294967296=-256898466‬

 

[Declan]

The first bit is the sign bit, that is, the first hex number is 8-F, the value is a negative, the number = number - 2^32.
it should be 4038068830-4294967296=-256898466‬

Yes, many thanks.
How would I calculate this in B4J?

 

[teddybear]

Yes, many thanks.
How would I calculate this in B4J?

In B4J it just is a sign int

    Dim Latitude As Int = 0x10D27FBC
    Dim Longitude As Int = 0xF0B00A5E
    Log(Latitude)  '282230716
    Log(Longitude) '-256898466

 

[Declan]

In B4J it just is a sign int

    Dim Latitude As Int = 0x10D27FBC
    Dim Longitude As Int = 0xF0B00A5E
    Log(Latitude)  '282230716
    Log(Longitude) '-256898466

Great, it works
But I get this error:

(NumberFormatException) java.lang.NumberFormatException: For input string: "10D2831F"

I must have the 0x before the 10D2831F (0x10D2831F)

 

[teddybear]

Great, it works
But I get this error:

(NumberFormatException) java.lang.NumberFormatException: For input string: "10D2831F"

I must have the 0x before the 10D2831F (0x10D2831F)

If you want to use a hexstring as input, you should convert the hexstring to int

    Dim bc As ByteConverter
    Dim b() As Byte=bc.HexToBytes("F0B00A5E")
    Dim Longitude() As Int=bc.IntsFromBytes(b)
    Log(Longitude(0))

 

[Declan]

If you want to use a hexstring as input, you should convert the hexstring to int

    Dim bc As ByteConverter
    Dim b() As Byte=bc.HexToBytes("F0B00A5E")
    Dim Longitude() As Int=bc.IntsFromBytes(b)
    Log(Longitude(0))

I have the following:

                Dim myLon As String
                myLon = raw.SubString2(66,74)
                
                Dim bc As ByteConverter
                Dim b() As Byte=bc.HexToBytes(myLon)
                Dim Longitude() As Int=bc.IntsFromBytes(b)
                Log(Longitude(0))

I get the following error on compile:

B4J Version: 9.80
Parsing code.    (0.01s)
    Java Version: 14
Building folders structure.    (0.02s)
Compiling code.    Error
Error compiling program.
Error description: Current declaration does not match previous one.
Previous: {Type=Int,Rank=0, RemoteObject=True}
Current: {Type=Int,Rank=1, RemoteObject=True}
Error occurred on line: 212
Dim Longitude() As Int=bc.IntsFromBytes(b)

 

[Daestrum]

Did you already have a variable named Longitude ?

 

[emexes]

Try:

Dim raw As String = "0123456789012345678901234567890123456789012345678901234567890.....F0B00A5E....."    'test sample

Dim myLon As String
myLon = raw.SubString2(66, 74)

Log(myLon)
 
'Dim bc As ByteConverter
'Dim b() As Byte=bc.HexToBytes(myLon)
'Dim Longitude() As Int=bc.IntsFromBytes(b)
'Log(Longitude(0))

Dim Longitude As Int = Bit.ParseLong(myLon, 16)    'there should be a law against this but, hey, if it works, it works
Log(Longitude)

Waiting for debugger to connect...
Program started.
F0B00A5E
-256898466

 

[Declan]

I have the following:

                Dim myLon As String
                myLon = raw.SubString2(66,74)
               
                Dim bc As ByteConverter
                Dim b() As Byte=bc.HexToBytes(myLon)
                Dim Longitude() As Int=bc.IntsFromBytes(b)
                Log(Longitude(0))

I get the following error on compile:

B4J Version: 9.80
Parsing code.    (0.01s)
    Java Version: 14
Building folders structure.    (0.02s)
Compiling code.    Error
Error compiling program.
Error description: Current declaration does not match previous one.
Previous: {Type=Int,Rank=0, RemoteObject=True}
Current: {Type=Int,Rank=1, RemoteObject=True}
Error occurred on line: 212
Dim Longitude() As Int=bc.IntsFromBytes(b)

Many thanks for all you assistance.
This works:

                Dim myLat As String
                Dim myLon As String
                myLat = raw.SubString2(58,66)
                myLon = raw.SubString2(66,74)
                    
                Dim b() As Byte=bc.HexToBytes(myLat)
                Dim Latitude() As Int=bc.IntsFromBytes(b)
                Log(Latitude(0))

                Dim b() As Byte=bc.HexToBytes(myLon)
                Dim Longitude() As Int=bc.IntsFromBytes(b)
                Log(Longitude(0))

                Log("Latitude: " & Latitude(0))
                Log("Longitude: " & Longitude(0))