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emonmuc header

This document describes how to prepare the serial port for emonmuc (energy monitoring multy utility communication), an open-source protocoll driver project to enable the communication with a variety of metering or other devices, developed based on the OpenMUC project.

1 Prepare the Serial Port

To use any serial port with the emonmuc framework, e.g. to communicate via Modbus RTU, the open-source project jRxTx is used. This, as well as some additional steps if the UART Pins of the Raspberry Pi Platform should be used, need to be prepared.

1.1 Install RXTX

RXTX is a Java native library providing serial and parallel communication for the Java virtual machine. It is a necessary dependency for many communication devices, using e.g. RS485.

To install, download the binaries via debian repository:

sudo apt-get install librxtx-java

2 Raspberry Pi

If the serial port is connected to the Raspberry Pi via e.g. an USB interface but the Raspberrys internal UART pins, you may skip this step.

By default, the serial port is configured as a console port for interacting with the Linux OS shell. To use the serial port in a software program, it must be disabled for the OS to use. To do this, sudo raspi-config can be used under Interfacing Options > Serial. This will promt two questions, of which the first should be answered <No> to disable the shell interfacing, and <Yes> for the second one, to still allow serial connections in general.

Make sure, the console does not connect to /dev/ttyAMA0/ in /boot/cmdline.txt

dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait

and /boot/config.txt to have UART enabled

enable_uart=1

Disable any reference, getty may have to it

sudo systemctl stop serial-getty@ttyAMA0.service
sudo systemctl disable serial-getty@ttyAMA0.service
sudo systemctl mask serial-getty@ttyAMA0.service

As soon as the system will be rebooted after completing the dependency configurations, the serial port will be prepared to use.

2.1 Raspberry Pi v3 Compatibility

This section only applies to Raspberry Pi v3 and later.

To avoid UART conflicts, it's necessary to disable Pi3 Bluetooth and restore UART0/ttyAMA0 over GPIOs 14 & 15;

sudo nano /boot/config.txt

Add to the end of the file

dtoverlay=pi3-disable-bt

Also, stop the Bluetooth modem trying to use UART

sudo systemctl disable hciuart

See the RasPi device tree commit for pi3-disable-bt and the forum thread discussion.