Lpc2000

Hi,
I try to read a 24 bits A/D converter from burr brown (ADS1252) with 
SPI interface. The converter send value in continue. There is data 
ready signal before the value on the data pin. I synchronize the read 
with an external interrupt (P0.15/EINT2 and MISO pin are connected 
together). The external interrupt runs well. But i don't understand 
how the SPI controler work :
I initialize the controler, the VIC interrupt for the SPI0 (see the 
code below).
- My first problem is I don't find in the user manual what start the 
SPI clock for a read. In other controler (ATMEL 89C51 for example, a 
0x00 write to the data register start the clock). 
- The second one is I have 8 clock bit on the SCLK line just at the 
startup an d before my first external interrupt (the one noramlly who 
start the SPI read...). I don't understand why I have got these 8 
clock bits ? After these clock the SPI seems to be blocked...

Thanks for your help,
Sebastien

//My initialisation code...
VICVectCntl0 = 0x0000002A; 
VICVectAddr0 = (unsigned)SPI_ISR;
VICIntEnable = 0x00000400;	

PINSEL0 |= 0x00005500;		
S0SPCCR	= 20;		
S0SPCR  = 0x000000A0;

--- In lpc2000@yahoogroups.com, "sebfr74" <sejacquemard@...> wrote:
>

> - My first problem is I don't find in the user manual what start the 
> SPI clock for a read. In other controler (ATMEL 89C51 for example, a 
> 0x00 write to the data register start the clock). 

I have not yet started my ARM SPI programs, but from the manual it
looks like a write to the SPI data register starts the transfer. 
Remember that SPI is just a circular shift register with one part in
the processor (usually 8 or 16 bits) and the rest in the SPI chip.  So
there are not separate reads and writes.  All transfers do both.

> - The second one is I have 8 clock bit on the SCLK line just at the 
> startup and before my first external interrupt (the one noramlly who 
> start the SPI read...). I don't understand why I have got these 8 
> clock bits ? 
SPI transfers are controlled by the number of clocks when select is
asserted, not the total number of clocks.  SPI even works with a free
running clock.  Maybe the clock starts before the first transfer.

After these clock the SPI seems to be blocked...

Your code has
S0SPCCR	= 20;
	
I think you want
S0SPCCR	= 0x20;	

Decimal 20 puts it in slave mode instead of master mode.

-- Bob H.

There is no difference between read and write. Just make dummy write if 
you want read. Look at ADC datasheet when it sends data back? Clock is 
allways generated by master (LPC in your case). I am using simple SPI 
transfer function:

unsigned char spi0_transfer(unsigned long dat) {
  S0SPDR  = dat;                    // send data
  while (!(S0SPSR & 0x80)) ;         // wait for transfer completed
  return S0SPDR;
}

I am not using ISR for SPI. Can you send your ISR for SPI?

Marko


sebfr74 wrote:

> Hi,
> I try to read a 24 bits A/D converter from burr brown (ADS1252) with
> SPI interface. The converter send value in continue. There is data
> ready signal before the value on the data pin. I synchronize the read
> with an external interrupt (P0.15/EINT2 and MISO pin are connected
> together). The external interrupt runs well. But i don't understand
> how the SPI controler work :
> I initialize the controler, the VIC interrupt for the SPI0 (see the
> code below).
> - My first problem is I don't find in the user manual what start the
> SPI clock for a read. In other controler (ATMEL 89C51 for example, a
> 0x00 write to the data register start the clock).
> - The second one is I have 8 clock bit on the SCLK line just at the
> startup an d before my first external interrupt (the one noramlly who
> start the SPI read...). I don't understand why I have got these 8
> clock bits ? After these clock the SPI seems to be blocked...
>
> Thanks for your help,
> Sebastien
>
> //My initialisation code...
> VICVectCntl0 = 0x0000002A;
> VICVectAddr0 = (unsigned)SPI_ISR;
> VICIntEnable = 0x00000400;     
>
> PINSEL0 |= 0x00005500;           
> S0SPCCR      = 20;           
> S0SPCR  = 0x000000A0;     
>
>
>
>
>
>
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Thanks it works fine today. Finally I don't use interrupt for the spi 
controller because I've got an external interrupt to start the read..
I use this code (I call read_ads1252() from the EINT2 interupt) :


uchar SPI_read()
{
	S0SPDR = 0xFF;
	while(!(S0SPSR & 0x80));
	return(S0SPDR);
}


void read_ads1252()
{
	mesure = (SPI_read() << 8); //bits 1 to 8
	mesure += SPI_read(); //bits 9 to 16
	SPI_read(); //read bits 17 to 24 not use 
}
Sebastien

--- In lpc2000@yahoogroups.com, "Marko Pavlin (home)" <mp@...> wrote:
>
> There is no difference between read and write. Just make dummy 
write if 
> you want read. Look at ADC datasheet when it sends data back? Clock 
is 
> allways generated by master (LPC in your case). I am using simple 
SPI 
> transfer function:
> 
> unsigned char spi0_transfer(unsigned long dat) {
>   S0SPDR  = dat;                    // send data
>   while (!(S0SPSR & 0x80)) ;         // wait for transfer completed
>   return S0SPDR;
> }
> 
> I am not using ISR for SPI. Can you send your ISR for SPI?

For the SPI isr I used the HITEX books SPI exemples.


> 
> Marko
> 
> 
> sebfr74 wrote:
> 
> > Hi,
> > I try to read a 24 bits A/D converter from burr brown (ADS1252) 
with
> > SPI interface. The converter send value in continue. There is data
> > ready signal before the value on the data pin. I synchronize the 
read
> > with an external interrupt (P0.15/EINT2 and MISO pin are connected
> > together). The external interrupt runs well. But i don't 
understand
> > how the SPI controler work :
> > I initialize the controler, the VIC interrupt for the SPI0 (see 
the
> > code below).
> > - My first problem is I don't find in the user manual what start 
the
> > SPI clock for a read. In other controler (ATMEL 89C51 for 
example, a
> > 0x00 write to the data register start the clock).
> > - The second one is I have 8 clock bit on the SCLK line just at 
the
> > startup an d before my first external interrupt (the one noramlly 
who
> > start the SPI read...). I don't understand why I have got these 8
> > clock bits ? After these clock the SPI seems to be blocked...
> >
> > Thanks for your help,
> > Sebastien
> >
> > //My initialisation code...
> > VICVectCntl0 = 0x0000002A;
> > VICVectAddr0 = (unsigned)SPI_ISR;
> > VICIntEnable = 0x00000400;     
> >
> > PINSEL0 |= 0x00005500;           
> > S0SPCCR      = 20;           
> > S0SPCR  = 0x000000A0;     
> >
> >
> >
> >
> >
> >
> > SPONSORED LINKS
> > Microcontrollers 
> > <http://groups.yahoo.com/gads?
t=ms&k=Microcontrollers&w1=Microcontrollers&w2=Microprocessor&w3=Intel
+microprocessors&w4=Pic+microcontrollers&c=4&s=95&.sig=mfaAujKZXA2Z_vx
re9sGnQ> 
> > 	Microprocessor 
> > <http://groups.yahoo.com/gads?
t=ms&k=Microprocessor&w1=Microcontrollers&w2=Microprocessor&w3=Intel+m
icroprocessors&w4=Pic+microcontrollers&c=4&s=95&.sig=9jjd2D3GOLIESVQss
LmLsA> 
> > 	Intel microprocessors 
> > <http://groups.yahoo.com/gads?
t=ms&k=Intel+microprocessors&w1=Microcontrollers&w2=Microprocessor&w3=
Intel+microprocessors&w4=Pic+microcontrollers&c=4&s=95&.sig=OMnZuqMZX9
5mgutt4B-tDw> 
> >
> > Pic microcontrollers 
> > <http://groups.yahoo.com/gads?
t=ms&k=Pic+microcontrollers&w1=Microcontrollers&w2=Microprocessor&w3=I
ntel+microprocessors&w4=Pic+microcontrollers&c=4&s=95&.sig=Malspbd0T4R
q3M4Q0nHrfw> 
> >
> >
> >
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