Combining 4 nibble to 16bits

[isaac]

Hi All
I am looking to get some advise of how i can combine four nibble (4bits x 4)
to give me 16bits so that i can shiftout the 16bits at once.
The device i am reading can only end 4bits at a time so i would have to receive the data four times and store this into 4 variables Nibble1-Nibble2
i would be receiving the data on PortD.0-PortD.3
The tricky bit for me i that i want Nibble1 to corresponds to Msb posistion
of my 16bits so for example if my values are as below

nibble1=F
nibble2=E
nibble3=D
nibble4=C
TRISD=$FF

Assuming at this point those values are in the var would this be ok
ShiftOut DataP,Clk,MsbFirst,[nibble1\4,nibble2\4,nibble3\4,nibble4\4] 'Send 16bits out

[HenrikOlsson]

Hi,
Perhaps something like this:

Result var word

'Nibble 1 is the 4 most significant bits, Nibble4 the 4 least significant.
'Most signinficant bit in nibble 1 is most significant bit in result.
Result = (Nibble1 * 4096) + (Nibble2*256) + (Nibble3 * 16) + Nibble4

Nibble1----Nibble2---Nibble3--Nibble4
0 0 1 0 - 1 1 0 0 - 0 0 0 1 - 1 1 1 0 = 11294(dec)

(2*4096)+(12*256)+(1*16)+14 = 11294

/Henrik Olsson.

[sayzer]

Hi Isaac,

It would be more helpful if you could explain what you need in more detail.

As much as I understood, reading the port pins individually could work for you.

Nibbles are BITs, not bytes.

nibble1 = PORTD.0
nibble2 = PORTD.1
nibble3 = PORTD.2
nibble4 = PORTD.3

Then you can take these four bits and use as you like.


Or am I on the wrong track here?


--------------------

[SteveB]

From what you have explained, here is something that should work:

Full_Word var Word
Low_Byte  var Full_Word.lowbyte
High_Byte Var Full_Word.Highbyte

'First Nibble
High_Byte = (PortD & %00001111)
High_Byte = High_Byte << 4
'Second Nibble
High_Byte = High_Byte + (PortD & %00001111)
'Third Nibble
Low_Byte = (PortD & %00001111)
Low_Byte = Low_Byte << 4
'Forth Nibble
Low_Byte = Low_Byte + (PortD & %00001111)
'Full_Word now has the 16 bit result of 4 Nibbles

HTH,
Steve

[i]EDIT: just changed port, since I miss read original post and used B instead of D

[isaac]

Sorry sayzer

if i didn't give enough explaination so here it is

I have 4 variables of 4bits each
Nibble1,Nibble2,Nibble3 and Nibble4
Lets assume that they contain the following values

nibble1=F which is binary 1111
nibble2=E which is binary 1110
nibble3=D which is binary 1101
nibble4=C which is binary 1100

i want to combine them to form a 16bit word variable say result
to make result=FEDC or 1111111011011100

Then i can use the shiftout command to send the value of result
as

ShiftOut DataP,Clk,MsbFirst,[result\16]

instead of as below as i presently do it

ShiftOut DataP,Clk,MsbFirst,[nibble1\4,nibble2\4,nibble3\4,nibble4\4]

Those are read in on PORTD.0 - PORTD3 one at a time as the device
i am reading is only capable of send 4bits at a time.
i think SteveB method might work though


Hope this is clear
Isaac

[isaac]

Thanks Henrik

i would give it a go just used my calculator and it comes out perfect

Isaac

[paul borgmeier]

No improvement over Henrik's version except about half the code space

;Result = (Nibble1 * 4096) + (Nibble2*256) + (Nibble3 * 16) + Nibble4

Result.highbyte =(Nibble1<<4)+Nibble2
Result.LowByte =(Nibble3<<4)+Nibble4

[mister_e]

i'm not sure you need to send it that way. I'm pretty sure it will work anyway if you send the whole word variable... no?

Same thing for reading from... in one shot.

Well i think. You never told what device you're using so...