Help with combining two data types into one

neochrome32 · Joined: 09 Jun 2013 Posts: 153

CCS C 4.130
dsPIC33 EP 512 GP 806

ok, I'm finding this a little frustrating, I use GCC to work on a routine, it normally works out very well on the pc. But when i come to port it to the chip. ccs.. it compiles but behaves differently!

the computer I'm just doing basic...

Ttelmah · Joined: 11 Mar 2010 Posts: 19546

This has been covered many times.

In C, the 'rule' is that maths type actually used, is the 'highest' of the two 'source' types in an expression. So if you add/multiply etc., an int8, by an int16, int16 maths will be used, even if the target is an int32.

However, on the PC, maths in general is done using the hardware maths unit, and this automatically 'extends' the type, if there is an overflow. Most C's will also do this, but CCS elected not to, to keep the maths code as small as possible. So on CCS, it is totally strict about sizes, and you need to cast to ensure that the type needed is used (only one value needs to be cast).

neochrome32 · Joined: 09 Jun 2013 Posts: 153

Thanks Ttelmah,

i did a search for this, but no result...
MPLAB appear to have elected it also then.

ok back to casting (type)value; it is.....

Man you know a lot!! i thought i knew C, C++ but I STILL fall into these traps!!!

thanks again Smile

also, thanks for the advice about the audio issue... i solved it, turns out im getting the noise while accessing the SDCARD so... looks like im rethinking the SDCARD dat lines... (it works, but not as fast as id like)