18.1
Format of data transfer at the serial interface
The interface works with a data rate of 4800 bauds, 8 data-bits, no parity and a Stopbit
.
The transfer of useful data takes place in lines. All characters are ASCII coded. All
information is sent continuously without separation characters. In one line, information of
only one channel is transferred. Each line closes with the character ‘Carriage return’ ‘<CR>´.
Several lines form a data-block. A data-block can have the following contents, for example :
@<CR>
I01010100B00725030178<CR>
V010892A1<CR>
I02020100B00725030148<CR>
V0216B0EA<CR>
$<CR>
The data block has a following structure
:
The starting sequence ´@ <CR>´
The Identifier of a channel. The line begins with the character ‘I’, followed by the logical
channel number, configuration data and the sensor serial number. The line is closed with
the check sum and the character ‘<CR>’. The identifier does not contain any measured
values.
The measured values of a channel. The data line begins with the character ´V´, followed
by the logical channel number and then by useful data (measured values). Only
numerical measurement values and two characters check sum (CRC) are transferred at
the end of the line.
The identifier and measured values follow the same scheme for all other channels.
The continuation character ´$´ <CR>´ is sent at the end of a data-block.
In TPK 20, the temperature values are transferred with channel 01 and humidity
values(relative humidity) are transferred with channel 02.
All information is represented in binary format and transferred in ASCII-encoded form
without separation characters.
Identification letter ´V´ at the beginning of the line, two ASCII -characters logical channel
number (01 for temperature, 02 for humidity), 4 ASCII -characters measurement data, 2
ASCII -characters checksum
The temperature has a resolution of 0.01 °C. The hexadecimal value is to be interpreted
as signed integer and to convert it into decimal number, it is to be divided by 100. With
this, one gets the temperature value in °C with two right comma places.
The humidity has a resolution of 0.005%. The hexadecimal value is to be changed into a
decimal number by dividing by 200. With this, one gets the humidity value rH in% with
two right comma places.
In the above shown example, the measured temperature is 21.94 °C and the air humidity
is 29.04% rH.
