Carlos J. Garcia-Orellana

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10 years, 7 months ago.

Problem with PTC1

Hello,

I'm trying to use a external display (arduino shield) that use PTC1 (A5) as WR signal. After some test, I've found that in that pin I have a square signal with a frequency of 32 KHz (0 to 3.3V). If I disconnect all and I write a program with PTC1 as DIgitalOut, and I put it to zero, then I get a square signal of same frequency, but with amplitude of 1.2 V.

If I connect the WR signal to PTB1, the display works fine.

Any ideas?

Best regards,

Carlos.

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

Erik -
10 years, 7 months ago.

PTC1 is (as you noticed) a 32kHz square wave signal generated by the interface chip which is connected to the SDA connector, it is used as RTC clock input by the KL25Z.

If you can connect it to another line just use that. Alternatively if you power it from the second USB port (the KL25 USB) I believe the interface chip isn't powered and it probably works. But then you need to switch USB ports everytime you upload a new program.

Accepted Answer

Alternatively you can remove R24 from the Freedom board.

posted by Jim Carver 24 May 2014

Thanks Erik. It's works.

posted by Carlos J. Garcia-Orellana 24 May 2014