Hardware Reference
In-Depth Information
Chapter 9
UART
The Raspberry Pi has a UART interface to allow it to perform serial data communications.
The data lines used are 3.3 V logic-level signals and should
not
be connected to TTL logic
(+5 V) (they also are
not RS-232 compatible)
. To communicate with equipment using
RS-232, you will need a converter module.
RS-232 Converter
While an industrious person could build their own RS-232 converter, there is little need to
do so when cheap converters are available.
Figure
9-1
shows a MAX232CSE chip interface that I use. (This unit supports only
the RX and TX lines.) When searching for a unit, be sure that you get one that works with
3 V logic levels. Some units work only with TTL (+5 V) logic, which would be harmful
to the Pi. The MAX232CSE chip will support 3 V operation when its VCC supply pin is
connected to +3 V.
Figure 9-1.
MAX232CSE interface
