Ethernet-Mux Overview¶
Theory Of Operation¶
The following image shows a high level overview of the internal Ethernet-Mux building blocks:
+------------------------------------------------------+
| |
| +-----+
| | | OUT A
| +-------->+ | (RJ45)
| | +-----+
| +--------+ | |
+-----+ | 1:2 +---------+ |
IN | +------------------>+ Analog | |
(RJ45) | | | Switch +---------+ |
+-----+ +-+----+-+ | |
| ^ ^ | +-----+
| | | +-------->+ | OUT B
| | | | | (RJ45)
| +---+ +---+ +-----+
| | | |
| | | |
| | +----+----+ |
| +--+--+ | | |
| | | | CANopen | |
| | | | Control | |
| +-----+ | | |
| Digital +----+----+ |
| Override ^ |
| (Pin Header) | |
| | |
| +--+--+ |
| | | |
+------------------------------| |-----------------+
+-----+
CANopen
+ Power
Input
(D-SUB 9)
The main component of the Ethernet-Mux is a high-bandwidth, low-resistance analog switch that switches the input connection to one of the two output connections. As long as the device is powered, the input is always connected to one of these two outputs.
Electrical Isolation¶
The analog switch and microcontroller inside the Ethernet-Mux operate relative to the GND-level of the power supply. Ethernet may, according to its specification, introduce a voltage difference between both ends of a connection. To comply with this requirement the Ethernet-Mux uses Ethernet magnetics to galvanically isolate the switch from the Ethernet connections.
Note
The input and outputs of the Ethernet-Mux are galvanically isolated. The Ethernet-Mux is thus only suitable for Ethernet and Ethernet-like protocols and can not be used as a general-purpose RJ45-to-RJ45 switch.
Internal connections¶
The Ethernet-Mux is designed as a transparent switch between the RJ45 sockets. That means that all pins are connected 1:1, for example: Pin 1 of the input is either connected to Pin 1 of Socket A or Socket B.
Modes of control¶
There are two modes of input available:
Control via a CANopen-inspired protocol using the D-SUB 9 connector.
Control via a general purpose input, bypassing the microcontroller and it’s software. This Input is not exposed at outside of the housing an using it is only recommended for experienced users.
The input mode is selected using a jumper inside the housing. The Ethernet-Mux is delivered with the jumper set to CAN-based control.
Control via CAN¶
In this mode a CANopen-inspired control protocol over a CAN bus is used to control the Ethernet-Mux. In this mode multiple devices can be connected to the CAN bus and controlled individually.
Control via internal input¶
In this mode the analog switch can be controlled by an external logic signal in an arbitrary fashion. This mode can be used if the desired switch pattern can not be achieved using the control via CAN. See Control via GPIO for more information.