User guide

10
According to the IrDA Physical Layer specification [12] for the signaling rates up to
115.2 kb/s, the data are send as a stream of frames. Each frame consists of Start Bit, 8
Data Bits and a Stop Bit. No Parity Bit is used. All bits are encoded using RZI (Return-
to-Zero-Inverted) modulation, that means that “0” is represented by a pulse with a
duration of 3/16 of a bit period, and “1” is represented by no pulse. Least significant bit is
transmitted first.
We use 9600 b/s transmission rate in our project.
Communication Protocol
The board transmits the 12-bit high and low period values (T1 and T2) as the series of
three frames: a, b and c. The value of T1 does not change a lot over the all temperature
range, the most significant 4 bits are always staying the same. That is why we transmit
only 8 least significant bits of T1.
The meaning of the 8-bit frames is following:
• first byte (a): T1[7:0]
• second byte (b): {000, T2[11:7]}
• third byte (c): {1, T2[6:0]}
For each measurement, two set of frames (a, b, c) are transmitted with the same values. In
one second five measurements are made and 10 sets of frames are transmitted.
aacb