Signal level of UART port

[Himanshu]

I am experimenting with the UART example. I can connect the nRF USB port to the USB port of my computer. I used realterm to see the serial output. The example works as described. My understanding is that the pin 0.06 (TXD) and pin 0.08 (RXD) are the real pins to generate the UART signal and they can be connected to RS232 port of computer (If a computer has one). In my opinion the USB connection is given on the DK to emulate the RS232 serial port behaviour.

My question is : - Can the pins 0.06 and 0.08 be connected to the RS232 port on the computer; if yes, do I have to worry about the voltage levels. ( Boards may generate 3.3 voltage level while it may not be compatible with voltage level of computer. Also are there any connection details. ( i.e. RXD to TXD of computer or RXD to RXD of computer).

Thanks in Advance

[Henry_Chou]

You may use the CDC usb to comport cable to your PC. Then the voltage level problems are okay. Else you need the level converter chips such as MAX232 ,ICL232 to convert the voltage from +/- 12V to 5V/GND. However, The NDK board provide the Virtual port directly, You may try it before your custom hardware. 

[Marjeris Romero]

Hi,

As it's pointed above I recommend you use the USB CDC ACM example if you want to communication between the nRF52840 and a PC, since nRF52840 has built-in support for USB.

The UART peripheral example uses the onboard segger chip on the DK as a UART-USB(DCD) brigde to redirect the UART output/input to the COM port.

Some RS232 ports have up to 25V levels, so you will not be able to connect the UART peripheral of the nRF52840 without a converter. RS232 is quite an old connector as well, so it's not really common for modern PC to have such a connector.

Best regards,

Marjeris