The MAX3232 TTL to RS-232 Interface Module uses built-in charge pumps to convert between TTL logic level serial and standard RS-232 ±V serial.
KEY FEATURES OF MAX3232 TTL TO RS-232 INTERFACE MODULE:These modules allow microcontrollers to interface their logic level TTL serial to the RS-232 standard that requires ± voltage signaling per the TIA/EIA-232-F spec. This also allows the RS-232 to be used over longer distances than when using TTL serial.
The module is based on the MAX3232 chip and can operate at 3.3 or 5V. It has two built-in charge pumps to provide the necessary ± voltages required to meet the RS-232 standard. Maximum bit rate is 120Kbit/s.
The maximum input receiver voltage range is ± 25V which will handle pretty much any RS232 that you are likely to connect to.
The main RS-232 connection is via a standard DB-9 Female connector, but a RS-232 2nd channel is also brought out to a header for connection flexibility.
DB-9 Connector
The module has a two 4-pin headers on the assembly. The 4-pin row near the edge of the board provides the main interface to use.
1 x 4 Header (Board edge side)
The other part of the header brings out the 2nd channel of the MAX3232 which might be useful in some applications.
1 x 4 Header (DB-9 side)
There is a red LED on the module that indicates transmit activity and a green LED that indicates receive activity.
The module has two holes for mounting.
At 3.3V Vcc, the RS-232 output swing was measured at ± 6V with no load and the TTL I/O is 5V tolerant, so it can be operated at 3.3V even when using with a 5V microprocessor. With a Vcc of 5V, the output swing was measured at ± 9V.
These modules work well and are simple to use and basically transparent in their operation. Just make sure that you have the TX/RX hooked up correctly along with power and ground.