[sdiy] How automatic is the DSP on the dsPIC33f??

[Tom Wiltshire]

On 20 May 2012, at 03:59, Eric Brombaugh wrote:

> On 05/19/2012 07:37 PM, dan snazelle wrote:
>> Lets say I program something in the C30 compiler for Mplab using the Dspic33fj64gp802 as the device.
>> in order to take advantage of things like MAC, and the things contained in the DSP library, is it necessary to program in some special way?
>> 
>> or does the C30 compiler do a good job of figuring out which sections of C code could and should be converted to code the DSP section of the DSPIC can process?
>> 
>> otherwise, without knowing how to implement the DSP section, it seems the dsPIC33f series would operate no differently than a PIC24 with a DAC built in.
> 
> While the C30 compiler claims to support the accumulators and has some limited intrinsics, when using standard C coding practices it doesn't know diddly about the DSP features. In order to maximize the use of the MAC you'll have to code in assembly language, explicitly invoke intrinsics or use the routines in the MCHP DSP library.
> 
> I typically code in a mixture of C and assembly - C for all the setup and control flow, with custom assembly functions linked in that handle all my DSP. It's fairly straightforward, but you do have to get up close and personal with the dsPIC instruction set. There's really no way around that. As you noted, without taking some special measures you might as well be using a PIC24.


I second that. I either use straight assembly, or C with assembly for the calculation routines.

T.