#define UART_TX_BUF_SIZE 1024
#define UART_RX_BUF_SIZE 1024
Why to send and receive buffer length of the definition of 1024 bytes, increase the value, again if serial port will not work
The size of UART_TX_BUF_SIZE/ UART_RX_BUF_SIZE is the RAM buffer size you want to reserve for uart library. You can change this define to increase or decrease the number as per your requirement but keeping the RAM size in mind. Note that the size of the buffers needs to be a power of 2.