Before starting to use a serial port in order to communicate with an external serial device, we must know the communication parameters it uses, that is, which are the specific configuration settings of the serial data we wish to transfer. So, we must know the speed, data-bits, parity, and stop-bits settings.
For the speed, only fixed values are typically allowed. In fact, we must choose from 75, 110, 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200 bit/s.
In reality, other speed settings can be used. You should carefully read the datasheet of the serial device to check the allowed baud rates.
Regarding data bits, the usual setting is 8 (that is, 8 bits are used to transfer the information) even if we can ...