9 years, 5 months ago.

Why is there a 32.79 kHz square wave output at PTC1?

I am using 20140530_k20dx128_kl25z_if_opensda.s19 firmware and with a blank program:

  1. include "mbed.h"

int main() { while(1) { } }

I am getting a 32.79 kHz 50% dutycycle squarewave output at PTC1. What is driving it? This waveform makes I2C inoperable.

If I reload the board with other firmware such as P&Emicro, the output goes away.

Question relating to:

The FRDM-KL25Z is an ultra-low-cost development platform for Kinetis L Series KL1x (KL14/15) and KL2x (KL24/25) MCUs built on ARM® Cortex™-M0+ processor. Features include easy access to MCU I/O, battery-ready, …

1 Answer

9 years, 5 months ago.

The signal is generated by the OpenSDA MCU to drive the RTC on the KL25Z. You can disconnect by removing R24 on the Freedom board

Accepted Answer

I might be a good idea to mark the presence of the clock signal on the pinout diagram.

posted by Shujen Chen 09 Dec 2015