CCS/CC2640R2F: Using uart sensor with cc2640r2f launchpad

Part Number: CC2640R2F

Tool/software: Code Composer Studio

Hello.
using the DIO3 / DIO2 pins on the cc2640r2f launchpad
I want to test a sensor that communicates with uart
Connecting RX / TX of sensor to DIO3 / DIO2 pin does not communicate
(Both read / write)
The default UART of launchpad is used for display
display doesn't even use init or open
Is there anything else I need to do to prevent the UART from being used for the display besides connecting a simple pin with H / W?

In the source code,
The callback of UART_read is not called and the resulting value is only -1.

 UART_Params_init (& uartParams);
    uartParams.readMode = UART_MODE_CALLBACK;
    uartParams.readCallback = uartCallback;
    uartParams.baudRate = 9600;
    uart = UART_open (Board_UART0, & uartParams);
    if (uart == NULL)
    {
        while (1);
    }

while (1) {
        UART_read (uart, & cmd, 1);
        sleep (1000);
    }