Is it possible to use a 12MHz crystal on the CLKIN/CLKOUT pins ?

[eft_flo]

Hello,

I have a 12 MHz crystal plugged on the LPC5410x that way :

But I am not able to start it and it no resonate. I tried to use the BOARD_USECLKINSRC=1 and BOARD_EXTCLKINRATE=12000000 flags from the LPCXpresso54102 BSP, but the crystal doesn't start.

I also tried to set the IRC first, and then enable the crystal by set the parameters to use the crystal (including set CLKOUT as an output and inverse the out pin to have a negative feedback loop). But no oscillation.

Does anyone succeed to use a crystal on these pin ? Do you have any example code working ?

Thanks for help.

[kerryzhou · Accepted solution]

Hi elf_flo,

   You can't connect the board like that.

 

 CLKIN should input the external clock directly, not the external crystal, this pin don't have the internal OSC module.

CLKOUT is used to monitor the internal clock:Main clock, clkin, IRC osciallator or watchdog oscillator frequency.

 So, if you want to use the 12Mhz, please input the 12Mhz frequency directly to the CLKIN pin.

Wish it helps you!

Have a great day,
Kerry

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