SAMD21 Pull Up Resistors

Jan 4th 2019

So if you are like me life has been great with the ARM Cortex parts.  Today the microprocessors are so awesome it is almost like heaven. 

For example no longer do you need add pull up resistors all over you PCBs when in the processor you can flip a bit and enable a pull up resistor on the pins.  This saves on the BOM cost and if you don't want to be pulled up in lower power just flip the bit. Life is Awesome.... 

So if you read the SAMD21 datasheet it awesome for example you want pull up on SERCOM pins no problem right there in the datasheet it states:

However when you actually go and test this it does not work... What the.... 

So you dig around and call the FAEs and create support tickets only find out that pin pull ups and pull downs are only functional when the pin is GPIO or EIC. What the....  Thank You Microchip I really wanted to spin my boards again to add resistors when you told me I did not need to. 

Lesson learned Microchip datasheets lie, and yes this bug exists in the SAMD51, SAMD20, SAML21 and most of microchips SAM parts. Yes they have known about the error in the datasheet for almost a year now and still have not fixed it.