SAM D20 Xplained Pro

Discussions around product based on ARM Cortex M0+ core.

Moderator: nferre

Posts: 1
Joined: Tue Jan 14, 2014 3:24 am

SAM D20 Xplained Pro

Tue Jan 14, 2014 3:38 am

Hello all,

I am trying to output a somewhat precise, has to be +- 250ppm, 32.768Khz clock on PA22 (GCLK6 output) but I am having a little problem. The chip outputs a clock that is around 32.90 KHz (I've seen it drop to 32.65.) The datasheet doesn't say anything about tolerance or accuracy of the internal clock system. (I am using the external crystal as the input to GCLK6.) I have attached some scope captures and below is the measurement data I captured with my oscilloscope.

Code: Select all

Vpp		5.52V			
Vmax		3.44V			
Vmin		-160mV			
Vavg		1.63V			
Vamp		3.23V			
Vtop		3.26V			
Vbase		-3.24mV			
Vrms		2.31V			
Vover		4.61%			
Vpre		2.21%			
Frequency	32.90kHz			
Rise Time	0.000s			
Fall Time	0.000s			
Period		30.40us			
Pulse Width+	15.20us			
Pulse Width-	15.20us			
Duty+		50.0%			
Duty-		49.8%	

clk.png (11.69 KiB) Viewed 1748 times

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