Specifications

77
the design team chose devices that could take advantage of this interface
standard.
Unfortunately, due to a restriction in multiple-device serial communications as
limited by the microcontroller hardware, it may be necessary to develop a
software process to either switch the device control held by the configurable
serial UART on the microcontroller, or emulate the hardware functionality of an
I²C bus controller. This can be accomplished utilizing a technique known as “Bit-
banging”. In this technique, software sets and samples the state of pins driven by
the microcontroller, and is responsible for all parameters required for the serial
communication standard.
The I²C requires only two lines. The first line is for serial data and is labeled SDA.
The other is a clock line labeled as SCL. Using a minimum number of bus lines
reduces the overall complexity and physical layout requirements for the
hardware. The target development board has 18 accessible pins, as seen in
Table 3.2.1-1. Fifteen of these pins are software configurable for the purpose of
sampling both analog and digital input, as well as driving analog and digital
output. For the purposes of communicating over the I²C bus, Pin 15 will be used
to drive the SCL line, and Pin 18 will be used to drive and sample the SDA line.
Table 3.2.1-1 EZ430-RF2500 Pinout Diagram, reprinted with permission granted
by Texas Instruments