This is what I use for uS timing. It has the advantage that the condition stays
true for 0x80000000 ticks, which means no worrying about missing the exact match
and going around again.
--- In l..., Robert Adsett wrote: >
> On 4/13/2010 5:34 PM, voltz56 wrote:
> >
> >
> > Hmmm, I still thought it would be possible to generate accurate
> > delays down a usec without using interrupts especially in a test
> > environment that is running no other code (just the delay routine).
> > Iv achieved this on an 8051 I didnt think it would be a problem
> > on....
>
> Some notes I made.
>
> http://www.aeolusdevelopment.com/AppNotes/LPC210X/an-timerperformance.pdf
>
> Non-interrupt based, but about 10uS overhead. That could be reduced by
> sacrificing dynamic range.
>
> Why do you need uS delays? uS precision is straightforward, single
> digit uS delays not so easy.
>
> Robert
>
> --
> http://www.aeolusdevelopment.com/
>
> From the Divided by a Common Language File (Edited to protect the guilty)
> ME - "I'd like to get Price and delivery for connector Part # XXXXX"
> Dist./Rep - "$X.XX Lead time 37 days"
> ME - "Anything we can do about lead time? 37 days seems a bit high."
> Dist./Rep - "that is the lead time given because our stock is live....
> we currently have stock."
>
On 4/13/2010 5:34 PM, voltz56 wrote: > Hmmm, I still thought it would be possible to
generate accurate
> delays down a usec without using interrupts especially in a test
> environment that is running no other code (just the delay routine).
> Iv achieved this on an 8051 I didnt think it would be a problem
> on....
From the Divided by a Common Language File (Edited to protect the guilty)
ME - "I'd like to get Price and delivery for connector Part # XXXXX"
Dist./Rep - "$X.XX Lead time 37 days"
ME - "Anything we can do about lead time? 37 days seems a bit high."
Dist./Rep - "that is the lead time given because our stock is live....
we currently have stock."
Reply by voltz56●April 15, 20102010-04-15
I'm beginning to think the keil software has a mind of its own. I just
tested again and now Im getting +20ns "every time". This I can live with. Thanks
for all your help.
Regards,
J
--- In l..., "Mark" wrote: >
> Hi
>
> At 48MHz there would be an increment once every 20ns.
> I don't know how well this clock is synchronised to the clock being used
for instruction execution - 20ns jitter is probably to be expected but I
can't explain +60..70ns every three interrupts. Maybe it is an accumulation
of the 20ns each time (?)
>
> Regards
>
> Mark
> --- In l..., "voltz56" wrote:
> >
> > Excellent that seems to have worked, thanks. Although every 3th interrupt is
off by +60 to 70ns, is that normal?
> >
> > Regards,
> > J
> >
> > --- In l..., "Mark" wrote:
> > >
> > > Hi
> > >
> > > I would try setting the pre-scaler to 0 and setting the match value to the
number of clocks that you require (0x30).
> > >
> > > Regards
> > >
> > > Mark
> > >
> > >
> > > http://www.uTasker.com
> > >
> > >
> > > --- In l..., "voltz56" wrote:
> > > >
> > > >
> > > > --- In l..., "voltz56" wrote:
> > > > >
> > > > > When I configure the prescaler for a 1ms tick, it is off by 84ns
> > > > when
> > > > > checked in the keil debugger, this much inaccuracy I can live with.
> > > > > , but when I have it configured for 1us it is off by approximately
> > > > > 940ns, this is a major problem for me.
> > > > >
> > > > > Regards,
> > > > > J
> > > > >
> > > > >
> > > > > //delay = us * no_loops
> > > > > void delay_us(unsigned int no_loops)
> > > > > {
> > > > > unsigned int i;
> > > > > for(i = 0; i < no_loops; i++)
> > > > > {
> > > > > //pclk = cclk = 48MHz
> > > > >
> > > > > T0_PR = 0x30; //Load Prescaler
register
> > > > for
> > > > > usec tick, formula --> toHex(interval/(1/pclk))
> > > > > T0_TCR = 0x00000003; //Reset counter and
> > > > prescaler
> > > > > T0_TCR = 0x00000001; //enable timer
> > > > > while ( T0_TC < 1);
> > > > > T0_TCR &= ~(1<<0); // Stop timer
> > > > > }/*end for*/
> > > > >
> > > > > }/*end delay*/
> > > > >
> > > >
> > > > Still no joy with this, anyone, any ideas or suggestions?
> > > >
> > > > http://pastebin.com/1j2b9G62
> > > >
> > > > Regards,
> > > > J
> > > >
> > >
>
Reply by Mark●April 15, 20102010-04-15
Hi
At 48MHz there would be an increment once every 20ns.
I don't know how well this clock is synchronised to the clock being used
for instruction execution - 20ns jitter is probably to be expected but I
can't explain +60..70ns every three interrupts. Maybe it is an accumulation
of the 20ns each time (?)
Regards
Mark
--- In l..., "voltz56" wrote: >
> Excellent that seems to have worked, thanks. Although every 3th interrupt is
off by +60 to 70ns, is that normal?
>
> Regards,
> J
>
> --- In l..., "Mark" wrote:
> >
> > Hi
> >
> > I would try setting the pre-scaler to 0 and setting the match value to the
number of clocks that you require (0x30).
> >
> > Regards
> >
> > Mark
> >
> >
> > http://www.uTasker.com
> >
> >
> > --- In l..., "voltz56" wrote:
> > >
> > >
> > > --- In l..., "voltz56" wrote:
> > > >
> > > > When I configure the prescaler for a 1ms tick, it is off by 84ns
> > > when
> > > > checked in the keil debugger, this much inaccuracy I can live with.
> > > > , but when I have it configured for 1us it is off by approximately
> > > > 940ns, this is a major problem for me.
> > > >
> > > > Regards,
> > > > J
> > > >
> > > >
> > > > //delay = us * no_loops
> > > > void delay_us(unsigned int no_loops)
> > > > {
> > > > unsigned int i;
> > > > for(i = 0; i < no_loops; i++)
> > > > {
> > > > //pclk = cclk = 48MHz
> > > >
> > > > T0_PR = 0x30; //Load Prescaler register
> > > for
> > > > usec tick, formula --> toHex(interval/(1/pclk))
> > > > T0_TCR = 0x00000003; //Reset counter and
> > > prescaler
> > > > T0_TCR = 0x00000001; //enable timer
> > > > while ( T0_TC < 1);
> > > > T0_TCR &= ~(1<<0); // Stop timer
> > > > }/*end for*/
> > > >
> > > > }/*end delay*/
> > > >
> > >
> > > Still no joy with this, anyone, any ideas or suggestions?
> > >
> > > http://pastebin.com/1j2b9G62
> > >
> > > Regards,
> > > J
> > >
>
Reply by voltz56●April 15, 20102010-04-15
Excellent that seems to have worked, thanks. Although every 3th interrupt is off
by +60 to 70ns, is that normal?
Regards,
J
--- In l..., "Mark" wrote: >
> Hi
>
> I would try setting the pre-scaler to 0 and setting the match value to the
number of clocks that you require (0x30).
>
> Regards
>
> Mark
> http://www.uTasker.com
> --- In l..., "voltz56" wrote:
> >
> >
> > --- In l..., "voltz56" wrote:
> > >
> > > When I configure the prescaler for a 1ms tick, it is off by 84ns
> > when
> > > checked in the keil debugger, this much inaccuracy I can live with.
> > > , but when I have it configured for 1us it is off by approximately
> > > 940ns, this is a major problem for me.
> > >
> > > Regards,
> > > J
> > >
> > >
> > > //delay = us * no_loops
> > > void delay_us(unsigned int no_loops)
> > > {
> > > unsigned int i;
> > > for(i = 0; i < no_loops; i++)
> > > {
> > > //pclk = cclk = 48MHz
> > >
> > > T0_PR = 0x30; //Load Prescaler register
> > for
> > > usec tick, formula --> toHex(interval/(1/pclk))
> > > T0_TCR = 0x00000003; //Reset counter and
> > prescaler
> > > T0_TCR = 0x00000001; //enable timer
> > > while ( T0_TC < 1);
> > > T0_TCR &= ~(1<<0); // Stop timer
> > > }/*end for*/
> > >
> > > }/*end delay*/
> > >
> >
> > Still no joy with this, anyone, any ideas or suggestions?
> >
> > http://pastebin.com/1j2b9G62
> >
> > Regards,
> > J
>
Reply by Mark●April 15, 20102010-04-15
Hi
I would try setting the pre-scaler to 0 and setting the match value to the
number of clocks that you require (0x30).
Regards
Mark http://www.uTasker.com
--- In l..., "voltz56" wrote: > --- In l..., "voltz56" wrote:
> >
> > When I configure the prescaler for a 1ms tick, it is off by 84ns
> when
> > checked in the keil debugger, this much inaccuracy I can live with.
> > , but when I have it configured for 1us it is off by approximately
> > 940ns, this is a major problem for me.
> >
> > Regards,
> > J
> >
> >
> > //delay = us * no_loops
> > void delay_us(unsigned int no_loops)
> > {
> > unsigned int i;
> > for(i = 0; i < no_loops; i++)
> > {
> > //pclk = cclk = 48MHz
> >
> > T0_PR = 0x30; //Load Prescaler register
> for
> > usec tick, formula --> toHex(interval/(1/pclk))
> > T0_TCR = 0x00000003; //Reset counter and
> prescaler
> > T0_TCR = 0x00000001; //enable timer
> > while ( T0_TC < 1);
> > T0_TCR &= ~(1<<0); // Stop timer
> > }/*end for*/
> >
> > }/*end delay*/
> > Still no joy with this, anyone, any ideas or suggestions?
>
> http://pastebin.com/1j2b9G62
>
> Regards,
> J
>
Reply by voltz56●April 15, 20102010-04-15
--- In l..., "voltz56" wrote: >
> When I configure the prescaler for a 1ms tick, it is off by 84ns when > checked in the keil debugger, this much inaccuracy I
can live with.
> , but when I have it configured for 1us it is off by approximately
> 940ns, this is a major problem for me.
>
> Regards,
> J
> //delay = us * no_loops
> void delay_us(unsigned int no_loops)
> {
> unsigned int i;
> for(i = 0; i < no_loops; i++)
> {
> //pclk = cclk = 48MHz
>
> T0_PR = 0x30; //Load Prescaler register for > usec tick, formula --> toHex(interval/(1/pclk))
> T0_TCR = 0x00000003; //Reset counter and prescaler > T0_TCR = 0x00000001; //enable
timer
> while ( T0_TC < 1);
> T0_TCR &= ~(1<<0); // Stop timer
> }/*end for*/
>
> }/*end delay*/
>
Still no joy with this, anyone, any ideas or suggestions?
--- In l..., "rtstofer" wrote: > > Well I think I spoke too soon. The interrupt is
firing, but Im still
> > having trouble with the interval accuracy. When configured for 1us the
> > interval measured in keil debugger is 190ns.
> >
> > http://pastebin.com/LneyYUq5
> >
> > Regards,
> > V
> > The value you are setting to T0_MCR seems a little odd.
>
> Richard
>
Ya just noticed that, think I accidentally assigned that to MCR instead of MR0
at some point when testing. That is not my problem though as I have just
checked.
Regards,
J
Reply by rtstofer●April 14, 20102010-04-14
> Well I think I spoke too soon. The interrupt is
firing, but Im still
> having trouble with the interval accuracy. When configured for 1us the
> interval measured in keil debugger is 190ns.
>
> http://pastebin.com/LneyYUq5 Regards,
> V
>
The value you are setting to T0_MCR seems a little odd.
Richard
Reply by voltz56●April 14, 20102010-04-14
--- In l..., "Mark" wrote: >
> --- In l..., "voltz56" vltzzzzzzz@ wrote:
> >
> > > I do not see any code turning on the power for the timers.
> > >
> > > regards,
> > > Charles
> > >
> >
> > Your joking right?
> >
> > I think the problem is with my startup file, -there doesnt appear to
> be
> > any code to enable/config interrupts, but Im unsure how to do this.
> >
> > http://pastebin.com/cDB2j3Sb
> >
> > Regards,
> > J
> > Hi
>
> All peripherals default to powered up on the LPC2106 so, as long as they > haven't been disabled to save power, a power up
is not necessary.
>
> The peripheral code looks OK so I would agree that the interrupt hasn't > been enabled to the core. This can be done in the
code as follows,
> depending on compiler:
>
> __enable_interrupt() - IAR intrinsic
> __enable_irq() - Keil intrinsic
>
> for GCC the following assembler can be called (extern void
> __irq_en(void) from C)
> .code 32
> .global __irq_en
> __irq_en:
> mrs r12, CPSR
> /* get present SR value */
> bic r12, r12, #0xC0
> /* remove IRQ and FIQ mask bits */
> msr CPSR_c, r12
> /* set new value to SR */
> bx lr
> /* return with interrupts enabled */
> Regards
>
> Mark
>
> www.uTasker.com
Well I think I spoke too soon. The interrupt is firing, but Im still
having trouble with the interval accuracy. When configured for 1us the
interval measured in keil debugger is 190ns.
