Raspberry Pi ver 2.0 UART connection with PC and Xbee
Like most other modern bare boards, the raspberry pi does not speak RS232 levels; it expects 3.3v levels that are inverted in sense, and exposing it to RS232 levels will probably destroy the internal iobuffers of the relevant pins if not the SoC overall.

Most people just use USB&lt;>logic-level serial converters with suitable I/O voltages rather than using one that converts to RS232 and then having to use an additional IC to convert that to logic level. (The USB interface chip itself speaks logic levels, so a cable with an RS232 connector is one that has an internal translator to RS232 levels between the USB chip and the outside world). But back in the days when development machines had native RS232 ports, yes, we used chips like the MAX*232.

Note that some devices - for example certain BeagleBone boards and some Android phones - actually have even lower voltage serial channels - these expect 1.x volts and would be damaged by 3.3v signals.