FRDM K64F UART Logical levels

[martinboton]

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

[kerryzhou · Accepted solution]

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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[martinboton]

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

[mjbcswitzerland]

Hi

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