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Have you enabled the 32.768 external oscillator in software?

Yes,I have enabled it by following word:

#define BV(n) (1 << (n))

#define XOSC_STB BV(6) /* XOSC: powered, stable=1 */
#define HFRC_STB BV(5) /* HFRCOSC: powered, stable=1 */
/* CLKCONCMD bit definitions */
#define OSC BV(6)
#define TICKSPD(x) (x << 3)
#define CLKSPD(x) (x << 0)
#define CLKCONCMD_32MHZ (0)
#define CLKCONCMD_16MHZ (CLKSPD(1) | TICKSPD(1) | OSC)
#define OSC_PD BV(2) /* Idle Osc: powered down=1 */

#define EXTERNAL_CRYSTAL_OSC 0x00 // external 32kHz XOSC
#define INTERNAL_RC_OSC 0x80 // internal 32kHz RCOSC

// For non-USB, assume external, unless an internal crystal is explicitly indicated.
#define XOSC32K_INSTALLED TRUE //FALSE TRUE
#if !defined (XOSC32K_INSTALLED) || (defined (XOSC32K_INSTALLED) && (XOSC32K_INSTALLED == TRUE))
#define OSC_32KHZ EXTERNAL_CRYSTAL_OSC
#else
#define OSC_32KHZ INTERNAL_RC_OSC
#endif

//START_HSOSC_XOSC
SLEEPCMD &= ~OSC_PD; /* start 16MHz RCOSC & 32MHz XOSC */
while (!(SLEEPSTA & XOSC_STB)); /* wait for stable 32MHz XOSC */

//SET_OSC_TO_HSOSC
CLKCONCMD = (CLKCONCMD & 0x80) | CLKCONCMD_16MHZ;
while ( (CLKCONSTA & ~0x80) != CLKCONCMD_16MHZ );

//SET_32KHZ_OSC
CLKCONCMD = (CLKCONCMD & ~0x80) | OSC_32KHZ;
while ( (CLKCONSTA & 0x80) != OSC_32KHZ );

//SET_OSC_TO_XOSC
CLKCONCMD = (CLKCONCMD & 0x80) | CLKCONCMD_32MHZ;
while ( (CLKCONSTA & ~0x80) != CLKCONCMD_32MHZ );

//STOP_HSOSC
SLEEPCMD |= OSC_PD; /* stop 16MHz RCOSC */

Hi,

We used the KeyFob for our reference design recently and had similar problems with the 32kHz osc.  The problem, as you've already surmised, had to do with the capacitor values.  I don't remember off the top of my head which caps we had to change, but will check later and get back to you.

-Steve

Hi

the first ，I should say thanks to you

I can only to say the 32 kHZ OSC is too sensitive to the capacitance value.

I try to change the Cl Value from 8p to 22pf ，the 32khz OSC still does not work。but the 32MHZ work well。

I follow the design guideline “AN100 - Crystal Selection Guide (Rev. A) ” try to resolve this problem .but it still does not work……

How do you know the oscillator is not running? The crystal waveform can be tricky to measure as the amplitude is very low

HI Eng351

   the most easy method is enable the CKOEN bit of PMUX registers

When this bit is set, the selected 32-kHz clock is output on one of the P0 pins

and we can measue to a pin of the P0 port

other method is use a Low parasitic capacitance  oscilloscope probe ，and  turn it to X10 position to measure the waveform……

and the last method is use the sleep timer to blink a LED with XOSC

and so on

Hi Yt,

With a Cl value of 12.5pF I would think 22pF should be the correct value for the load capacitors.

Are you sure your footprint for the crystal is correct? Crystal pins are pin 1 and 3, and pin 2 should be connected to ground.

/Fredrik

Those cap values look fine to me... we had to change ours to 12-15 pf for both oscillators.  Don't see any reason why those wouldn't work.

yt

HI Eng351

   the most easy method is enable the CKOEN bit of PMUX registers

When this bit is set, the selected 32-kHz clock is output on one of the P0 pins

and we can measue to a pin of the P0 port

other method is use a Low parasitic capacitance  oscilloscope probe ，and  turn it to X10 position to measure the waveform……

and the last method is use the sleep timer to blink a LED with XOSC

and so on

 

Was just checking you knew how to check it is running - clearly you do :)

HI Fredrik K

Like you say，I have tried to calculate the compliance with design guidelines。

(C1*C2)/(C1+C2) =CL’   ，

C1=C2，

CL ‘= CL+（2~8pf）

the results is 22pf

but the XOSC still dose not work

finally，I had to re-release a version of the PCB to a larger PCB manufacturers。 

on the new version PCB ，I use the CL VALUE of 12pf with the 12.5 pf Recommended in the crystal Data Sheet，and it work well

when I change the CL value from 12pf to 22pf by Calculated through the empirical formula ，It is not working too

so i had to change back to 12pf

now it work well

so i think the last version PCB’s Quality is too bad 。and i also think the 32k osc function is too sensitive Compared with the 32M

Hi Eng351

   you know it

  thank you all the same

From our experience with the CC2511 the 32K osc. circuit was extremely sensitive to "dirt" on the circuit.

On our first design we used a leaded Xtal device which was hand soldered with no clean flux, and on some boards this lead to very slow start-up times for the oscillator.

As a work around we added code in the cold boot start-up procedure to check the 32K (Sleep Timer) counter against a counter running from the CPU clock before making a jump to the main firmware code.

After changing to an SMT Xtal we have not experienced start-up FAILURES, but we have kept the "cold boot start-up procedure" in the firmware just in case. (Note: this was NOT a Xtal / CL selection - suitability issue).

If the CC254x is similar to the CC2511, you may experience the same type of problems, especially after doing some re-soldering work. Make plenty of prototype boards and be willing to toss them if they start giving you trouble.

Also remember about Static Discharge.

Karel

Hi Karel

thank you for your experience.If I encounter this problem, I will try your approach

I will continue to update my latest progress

A note I use ABS07-32.768KHZ-T with 12p caps and have never had a problem with osc.

Hi Eng351

thank you for your reply

Now I use epson FC-135 with 12p and it works well.But I re-released version of the PCB，and find a bigger manufacturers