How to combine two 8 bit numbers to make a 16 bit number??

[jaybee]

Hi

My electronics ADC ouputs the result of the conversion over two bytes because it is a 10 bit number. This is then fed into Labview via the serial port. I have the two bytes stored in the various elements of an unbundle block diagram.

My current vi has the two bytes stored seperately. HOw may I combine the two together??

So far I have

1st byte sent : (MSB)bit7/bit6/bit5/bit4/bit3/bit2/bit1/bit0(LSB)
2nd byte sent : (MSB)X/X/X/X/X/X/bit1/bit0(LSB)

I can send the two bytes from my electronics in either order, whichever suits labview the best.

At the present time, byte 1 max value is 255 and byte to is 3

I would like to combine these two arrays to form the following:

(MSB)X/X/X/X/X/X/bit9/bit8/bit7/bit6/bit5/bit4/bit3/bit2/bit1/bit0(LSB)

This way, the combined two bytes has a range up to 1048, a true representation of the ADC value. This value can then be converted and displayed on a dial.

If anybody has any ideas or help it would be appreciated. I can attach a vi to explain what I am doing if that helps/or my details above are unclear.

Thanks

[becktho]

Hi

There's a function called "Join Numbers" in the Advanced>>Data Manipulation palette.

This function joins two numbers.

Just have a try.

Hope this helps.

Thomas

[Donald]

Try the 'Join Numbers' function in Functions>Advanced>Data Manipulation palette.

[jaybee]

Brilliant. Thanks

Will try that and see if I can get it to work.

[waldemar.hersacher]

"Join Numbers" will not work if bit1 of byte 2 is a sign bit. "Join Numbers" does not know that you have a 10 bit signed integer. In this case you need to make sign expansion on your own.

Use "join Numbers" to get the 16 bit representation. Then mask (0x0400) out bit 9 with an And. If the bit is set then set bit 10 to 15 by Oring with the right mask (0xFC00).

[stefan!]

Hello Waldemar,

can you send me your example code?

Regards, Stefan

[altenbach]

Since the resulting 10bit number has a range of 0 to 1023 (and that is what you want), you don't need to worry about sign bits. "Join numbers" will work just fine straight off the shelf. 🙂

[waldemar.hersacher]

Sign extention of a 10 bit integer. Input two bytes, Output signextended 10 Bit. The output value will be in the range from -512 to 511. No check if Highbyte is greater than 3!
Code in LV 6.0.2

[stefan!]

Hi Waldemar,

I like your code very much!!!
I changed it a bit and made some comments.

Regards, Stefan

[stefan!]

and the code ...