VAF instruments PEM2, Technical Manual

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7. Only applicable if RS485 output signal is required from the touch screen to an external system like
an AMS or external Efficiency Monitoring System.
Additional systems are connected to the COM1 output port as described in item 6 and Figure 6.
From the COM1, DB9 connector on the backside of the touch screen you can communicate through
Modbus with the PEM2 touch screen and read out the registers. The pin out of the connector is:

1 to B (DATA +)

6 to A (DATA -)

5 to GND.
The settings to communicate with the touchscreen are:

Serial interface RS485

Communication protocol Modbus RTU

Baud rate 115200

Data bits 8

Stop bits 1

Parity None

Function code 3 (Holding Registers)
All the by VAF Instruments presented register addresses are described in a file called “T-
Sense
®
_Modbus_tags”. In this file the applicable register address and corresponding units of the
read-out values can be found. Please contact VAF in case you like to receive this file or if you like to
have more information about the Modbus communication.
Be aware that the Modbus read-out values are presented as two 16-bits integers, which have to be
converted to a 32-bits float. A 32-bits IEEE 754 floating point number is a mathematical formula that
allows any real number with decimal points to be represented by 32-bits with an accuracy of seven
digits. For more info please check the IEEE 754 standard for binary floating point arithmetic.