topic FRDM K64F UART Logical levels in Kinetis Microcontrollers

FRDM K64F UART Logical levels

martinboton — Mon, 01 Aug 2016 16:26:55 GMT

Hi everyone,

I got a noob question about the FRDM k64f board :

I'm trying to set a RS232 communication with another device using UART2, the chars are well sent but the logical levels are weird : on my scope the high level of my data is about 500mV. Shouldn't it be 3.3V ?

Regards,

Martin

Re: FRDM K64F UART Logical levels

mjbcswitzerland — Mon, 01 Aug 2016 18:00:22 GMT

Are you sure you haven't connected the RS232 transceiver incorrectly (driving the UART2_TX line)?

If you want to check with a firmware which correctly drives the UART2_TX output, load the binary "USB-CDC with 5 UARTs" at http://www.utasker.com/kinetis/FRDM-K64F.html

You can then perform VCOM to UART bridges to all of the K64's UARTs to test yours (UART2_TX on PTD3) and any other UARTs that you may need.

Regards

Mark

Re: FRDM K64F UART Logical levels

kerryzhou — Tue, 02 Aug 2016 05:29:42 GMT

Hi Martin,

I think you also need to check your scope and probe configuration, you can test the on board fixed 3.3.V, is that correct on your scope?

Have a great day,
Jingjing

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Re: FRDM K64F UART Logical levels

martinboton — Tue, 02 Aug 2016 12:30:40 GMT

Yeah my scope and probe configuration are correct and the 3.3V is ok on my board(s).

Sending 'ESC' char at 115200 bauds :

I am going to test Mark Butcher's firmware right now to see what happens.

Thanks for your replies.

Martin