Re: [avr-gcc-list] General programming question/GPS parsing

[Bernard Fouché]

Matthew MacClary a écrit :

>   I have a general question, right now we parse the GPS sentence
>
> inside the USART interrupt.  I would like to have the interrupt only
> receive the data and write it to a buffer, how would I then tell
> another function to parse the buffer with interrupts enabled?  Can I
> just do a sei() inside of SIGNAL to turn interrupts on and then call
> the parsing function?
>
>  Thanks!
>
> -Matt
Hi Matt.

I think it's better to keep interrupts the shortest possible. What I'm 
doing on our current project:

- A character is received under interruption from the USART and stored 
in a circular buffer with a read and a write pointer.
- The main program loop polls the buffer to see if a character is 
available or not. If a character is available, it is retreived and 
parsing is done.
- If parsing is completed for a sentence, actions are done.

So that's the typical sheme, with a main central loop and buffers 
managed by interrupt driven routines that only get/put characters in 
circulars buffers. All 'intelligent' processing is done in the central 
loop if there is enough data, code is kept minimal inside routines 
called by interrupts.

Of course interrupt management is important since you don't want to 
process an incomming character (and/or an outgoing character if you are 
transmitting also under interrupt)  while the main central loop 
manipulates the read/write pointer values of the circular buffer. (for 
instance)

Don't forget to use the 'volatile' keyword on variables that can be 
changed in the main program loop and in a routine activated by an 
interruption. (again the read/write pointer values and eventually the 
count of available characters in the buffer or anything else involved in 
a similar way)

 Bernard