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gpio/atsamd51/index.html

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 <figcaption>Ring oscillator with ATSAMD51J19</figcaption>
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-<p>This ring oscillator runs on the ATSAMD51J19 MCU using the Adafruit Feather dev board.  The ATSAMD51J19 has an ARM Cortex-M4 running with a max speed of 120 MHz.  Code for the oscillator is available <a href='ring.ino'>here</a>, or visible below.</p>
+<p>This ring oscillator runs on the ATSAMD51J19 MCU using the Adafruit Feather dev board (though dev board price comes from <a href='https://www.adafruit.com/product/3800'>Adafruit ItsyBitsy M4 Express</a>).  The ATSAMD51J19 has an ARM Cortex-M4 running with a max speed of 120 MHz.  Code for the oscillator is available <a href='ring.ino'>here</a>, or visible below.</p>
 
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