Software SPI

Hi,

Could anyone give me AVR source code to implement SPI by software? I
need it because I want to have SPI and also external interrupt on
ATTiny22. But the pins are overlapped if the two functions are used.

Thanks!

"terry" <leonlai2k@yahoo.com> wrote in message 
news:9904d48.0411150142.1e635596@posting.google.com...
> Hi,
>
> Could anyone give me AVR source code to implement SPI by software? I
> need it because I want to have SPI and also external interrupt on
> ATTiny22. But the pins are overlapped if the two functions are used.


Atmel has an app. note with software SPI receive. I modified it for transmit 
using a '2313, and it worked fine, communicating with a PIC with hardware 
SPI.

Leon
-- 
Leon Heller, G1HSM
http://www.geocities.com/leon_heller 

"Leon Heller" <leon_heller@hotmail.com> wrote in message 
news:41988911$0$15428$cc9e4d1f@news-text.dial.pipex.com...
> "terry" <leonlai2k@yahoo.com> wrote in message 
> news:9904d48.0411150142.1e635596@posting.google.com...
>> Hi,
>>
>> Could anyone give me AVR source code to implement SPI by software? I
>> need it because I want to have SPI and also external interrupt on
>> ATTiny22. But the pins are overlapped if the two functions are used.
>
>
> Atmel has an app. note with software SPI receive. I modified it for 
> transmit using a '2313, and it worked fine, communicating with a PIC with 
> hardware SPI.

Sorry, that should read SPI master instead of  SPI receive. I actually 
modified it for slave operation, with a PIC SPI master.

Leon 

Leon Heller wrote:
> "Leon Heller" <leon_heller@hotmail.com> wrote in message 
> news:41988911$0$15428$cc9e4d1f@news-text.dial.pipex.com...
> 
>>"terry" <leonlai2k@yahoo.com> wrote in message 
>>news:9904d48.0411150142.1e635596@posting.google.com...
>>
>>>Hi,
>>>
>>>Could anyone give me AVR source code to implement SPI by software? I
>>>need it because I want to have SPI and also external interrupt on
>>>ATTiny22. But the pins are overlapped if the two functions are used.
>>
>>
>>Atmel has an app. note with software SPI receive. I modified it for 
>>transmit using a '2313, and it worked fine, communicating with a PIC with 
>>hardware SPI.
> 
> 
> Sorry, that should read SPI master instead of  SPI receive. I actually 
> modified it for slave operation, with a PIC SPI master.
> 
> Leon 


Please note that a software SPI slave is in a very difficult
timing position: all transfers are timed solely by the master
and the slave must be fast enough to keep up, This will usually
mean thet the slave has to use most of the processing time
polling the SPI clock.

-- 

Tauno Voipio
tauno voipio (at) iki fi

> Please note that a software SPI slave is in a very difficult
> timing position: all transfers are timed solely by the master
> and the slave must be fast enough to keep up, This will usually
> mean thet the slave has to use most of the processing time
> polling the SPI clock.

Polling? Why not interrupt-on-change?

Tauno Voipio <tauno.voipio@iki.fi.NOSPAM.invalid> wrote in message news:<Hgimd.31$y75.0@read3.inet.fi>...
> Leon Heller wrote:
> > "Leon Heller" <leon_heller@hotmail.com> wrote in message 
> > news:41988911$0$15428$cc9e4d1f@news-text.dial.pipex.com...
> > 
> >>"terry" <leonlai2k@yahoo.com> wrote in message 
> >>news:9904d48.0411150142.1e635596@posting.google.com...
> >>
> >>>Hi,
> >>>
> >>>Could anyone give me AVR source code to implement SPI by software? I
> >>>need it because I want to have SPI and also external interrupt on
> >>>ATTiny22. But the pins are overlapped if the two functions are used.
> >>
> >>
> >>Atmel has an app. note with software SPI receive. I modified it for 
> >>transmit using a '2313, and it worked fine, communicating with a PIC with 
> >>hardware SPI.
> > 
> > 
> > Sorry, that should read SPI master instead of  SPI receive. I actually 
> > modified it for slave operation, with a PIC SPI master.
> > 
> > Leon 
> 
> 
> Please note that a software SPI slave is in a very difficult
> timing position: all transfers are timed solely by the master
> and the slave must be fast enough to keep up, This will usually
> mean thet the slave has to use most of the processing time
> polling the SPI clock.


Thanks!

"Lewin A.R.W. Edwards" <larwe@larwe.com> wrote in message 
news:608b6569.0411160429.54257c12@posting.google.com...
>> Please note that a software SPI slave is in a very difficult
>> timing position: all transfers are timed solely by the master
>> and the slave must be fast enough to keep up, This will usually
>> mean thet the slave has to use most of the processing time
>> polling the SPI clock.
>
> Polling? Why not interrupt-on-change?

Probably because the original poster wanted to use the interrupt for 
something else. Sound like he needs to rethink the problem.

Peter