Shujen Chen

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10 years 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:

Last updated: 30 Jun 2020
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

Jim Carver
10 years 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