AnsweredAssumed Answered

KL03 pin mux is pointless?

Question asked by Michael Haffner on Jun 26, 2016
Latest reply on Jun 27, 2016 by Kerry Zhou

Hi all!

I recently discovered the Kinetis family and I'm really impressed about the features, power, size and price of these little friends: Having a 12bit ADC and powerful and matured TPM in a QFN16 is pretty cool.

I'd love to use them!!

But when it comes to the pin layout, the so called pin multiplexer is just a huge show stopper! Of course I want to use the builtin UART bootloader and a VREF, to make use of the nice 12bit ADC. But you cannot connect an external VREF and you cannot even use the internal one (needs 100nF at VREF_OUT), because it collides with PTB2, the UART_RX for the internal bootloader.

This is just a deadlock!

Even a fixed pin layout would be much nicer here. And the chip designers would have noticed the dilemma in the first place...

Of course, for a very small device with a low pin count, you probably need a multiplexer to decide which feature to which pin. Because there are more features than pins. But designing two very important features to be available on only one pin, both immovable, does not solve the task of a multiplexer.