A Bit manipulation brain teaser for you :)

[dw_picbasic]

Cool!..... Yes,
Then I could write a book and title it "Picing up the PC"

[mister_e]

But how do do it in a PIC where your greatest mathmatic result is limited to <= 65535?

Well, you place those limitation yourself. You could still use 2 Words... some basic maths around that. But will this worth if you could do most of the job on your PC side? It's up to you.

[HenrikOlsson]

Hi,
I don't want to pretend I know the answer but may have an idea....
What do you intend to with the value once (if) you have it?

/Henrik Olsson.

[Melanie]

I have 4 (8 bit) bytes being sent to me in a serial string.

Byte_1 is to be multiplied by 16777216
Byte_2 is to be multiplied by 65536
Byte_3 is to be multiplied by 256
Byte_4 is to be multiplied by 1

Not exactly a Brain Teaser - more a trick question.

Byte_1 is the MSB of a 32-bit variable, Byte_4 is the LSB of your 32-bit variable... no maths needed... so what you're really asking for is a routine to output a 32-bit (four byte) variable in human readable decimal...

[dw_picbasic]

Hi Melanie,
I thought I posted this the other day, but perhaps the system kicked me out for not posting fast enough.

The 4 bytes represent a value from 0 - 30,000.000
So fortunatly for me, the highest Byte will only be a 1 or 0.
The numbers represent radio frequency.
I have a radio that is sending me the 4 bytes to indicate what its current frequency is.
I have a number of frequency windows to play in.
I split each one of these windows up into 8 slices.
The frequency value then gets matched to one of these slices.
I use this info to control a remote antenna tuner box I made last winter.
I would bet you call this one simple.
But its over my head
Thanks
Duane

[sayzer]

...
The 4 bytes represent a value from 0 - 30,000.000

Can you split 30,000 from .000?

If you can, then you can put 30,000 into a word variable, and the remaining three zeros (.000) can get into another word variable (in theory).

If of course this is only for display purposes!


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

[mister_e]

how the data is sent? Did you tried to attach your radio directly to a PC? Maybe he just send you ASCII string or HEX value?

in fact it could make sense... let's assume it send you 4 Bytes...
30,000.000

[dw_picbasic]

Yes, the device is setup to talk to a PC.
The PC queries the device for its set frequency, and the device returns the 4 bytes.

I know I should push the 4 bytes into 2 seperate 16 bit words.
Then I need to figure out what the decimal part is for:

Millions
Thousands
Hundreds

This seem pretty straight forward for a 1 byte word, but no so easy for me to get my head around doing it for 2 bytes, due to the carry effect.