eepty
Full Member level 2
I have a ARM M0+ MCU connected with a 32.768KHz crystal. The crystal is connected to a load capacitor on each of its lead. The load capacitors are connected in parallel so one of its lead connected to the crystal and another lead connected to the reference ground.
I have made a number of board and they run normally. However recently I make some more boards and I found that the device seems paused for several seconds after power on. The observation is after I power on the device, it run normally for about 20seconds, and then it paused for about 30seconds, and then it runs normally again.
To try to investigate the problem, I modify the software to generate a pwm signal at one of the MCU pin, the pwm signal's clock source is the external 32.768KHz crystal. Having checked with a oscilloscope, I found the pwm signal start at the very begining when I power on the device, and then it paused for a while, and then it returns normal again. (Note: I am checking the pwm signal output from a MCU lead instead of chekcing the crystal lead directly, because I found that the crystal lead signal stopped when I touch the probe to it).
Then I changed the crystal to a new one, the pwm signal does not pause anymore.
Then I solder back the original crystal to the board, it runs normal again!8-O (That is it does not pause anymore after power on)
The original crystal was new and was bought from a trusted supplier
I would like to ask what can cause this problem?:thinker:
Thanks a lot!
I have made a number of board and they run normally. However recently I make some more boards and I found that the device seems paused for several seconds after power on. The observation is after I power on the device, it run normally for about 20seconds, and then it paused for about 30seconds, and then it runs normally again.
To try to investigate the problem, I modify the software to generate a pwm signal at one of the MCU pin, the pwm signal's clock source is the external 32.768KHz crystal. Having checked with a oscilloscope, I found the pwm signal start at the very begining when I power on the device, and then it paused for a while, and then it returns normal again. (Note: I am checking the pwm signal output from a MCU lead instead of chekcing the crystal lead directly, because I found that the crystal lead signal stopped when I touch the probe to it).
Then I changed the crystal to a new one, the pwm signal does not pause anymore.
Then I solder back the original crystal to the board, it runs normal again!8-O (That is it does not pause anymore after power on)
The original crystal was new and was bought from a trusted supplier
I would like to ask what can cause this problem?:thinker:
Thanks a lot!