topic Re: UART on kl25z in Kinetis Microcontrollers

UART on kl25z

aayushm — Fri, 14 Mar 2014 19:53:06 GMT

What is the differnce between UART0, UART1, UART2 on kl25z ?

What is the operating voltage of RX/TX pin of kl25z ?

Re: UART on kl25z

gibbon1 — Sat, 15 Mar 2014 00:58:35 GMT

The big difference is that UART0 has more clock options than UART1 and UART2. See system Options Register 2 (SIM_SOPT2) in the data sheet. UART1 and 2 use the same clock as runs the processor core.

In my case I'm constantly switching off the FLL clock and running the uP off the internal 4MHz clock to save power. By using the 4MHz clock to run UART0 I don't have to worry about data being sent out the uart getting corrupted.

I think there are also some features to automatically wake the uart up when the tx line toggles on UART0.

Re: UART on kl25z

aayushm — Sat, 15 Mar 2014 07:06:46 GMT

Thanks gibbon1 . That is a very useful information.

Can you please tell me, What is the operating voltage of rx/tx uart line?

Re: UART on kl25z

gibbon1 — Sat, 15 Mar 2014 08:12:42 GMT

Generally I think they are just standard CMOS voltage levels, typically 3.3V logic. If you want actual RS232 or RS485 signal levels you need an interface chip. For development stuff I use a USB to 3.3V serial cable see link below. to talk to the processor serial port.

http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232R_CABLES.pdf

Re: UART on kl25z

Hui_Ma — Mon, 17 Mar 2014 05:43:04 GMT

Please check my colleague comments at below thread:

UART on kl25z

Wish it helps.

Best regards,
Ma Hui

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