GCA101: LocoNet-TCP/IP

GCA101 EtherNet-LocoNet Bridge

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• TheGCA modules

Your train is going into the next generation .. ON ETHERNET!
This will be the ultimate solution for communication between Rocrail and LocoNet.
Almost each in the market available computer now-a-days is equipped with an Ethernet connection.
The USB does not always seem to be the perfect solution as substitute for the RS232 Comm port.

• UDP Multicast communication
• solid GCA-Compatible power supply
• isolated coupling between PC and Ethernet
• on-board ICSP for easier development and self programming of ATmel processor
• on-board Dip-Switch for selection a dedicated range of IP-adresses
• Starting in Version 2.1 an extra program is available to set your own IP adress.
• 2 x RJ12 connector for standard LocoNet periferie
• 2 x D-sub9 MGV-LocoNet connectors
• clear on-board indication of present power and Ethernet/LocoNet functions
• entirely compatible with all LocoNet commands
• fully supported by Rocrail

The GCA101 is equipped with a special Ethernet connector. It provides an electric isolation , which means that computer and your trains are not electrically connected together.
The standard Ethernet cable can be one of the two types. Either normal or 'crossed' cables are useful.

Various Laptops appear not to have enough capacity on the Ethernet connector.
Due to the galvanic isolation of the ethernet connection on MGV101 there is some more power needed.
In these situations, a left over router will solve the problem.

Two processors on this board are installed.
One to connect Ethernet to the standard SPI and the second as interface between SPI and LocoNet.
The unit is equipped with two standard LocoNet RJ12 connectors and two D-con-LocoNet connectors.
On board power switching power supply with 3 Amp output to be able to supply a large range of Loco I/O modules MGV50 I/O modules and MGV141 wheelcounters.
Compatible with all standard LocoNet units from Digitrax or Uhlenbrock, the Fremo FredI and MGV124.

The necessary transformer should have minimum of 52 VA.
Power supply : between 15V and 30V dc or between 12V and 24V ac.
Transformer or adapter MUST be dedicated ONLY for MGV101. No other connections should be made to transformer!
Ignoring this can result in damage of MGV101 or connected periphery.

Unit is available as board only or as complete parts package, including programmed processors.
Ready built units will not be available.

Thanks to Robert Evers & Fred Jansen who have put much energy in getting the system up and running, you will finally be able to run Rocrail and LocoNet without USB and/or RS232.

This is the most recent .hex file for U1

The three green leds in front are indicating different functions.

Important note !! :

Remove both jumpers if central station (i.e. Intellibox, Twincenter, Digitrax) is connected to J5 or J6.

The GCA101 is provided with a programming connector ICSP1.
A programmer with suitable software is the mySmartUSB-light: http://shop.myavr.com/index.php?sp=pages/startpage.htm
It connects directly from USB to GCA101.

Flashing the firmware is easy with avrdude:

avrdude -F -pm168 -cstk500v2 -P/dev/ttyUSB0 -Uflash:w:MGV101_UDP_TEST.hex:a

The programmer ID is “mySmartUSB Light” firmware version dependent: stk500v2 or avr910/911.

The protocol is 100% identical with all other LocoNet Buffers.
The LocoNet packets are send/received with Datagrams between Rocrail and the MGV101.

1. First start with all resistors and IC sockets.
2. For socket of U2, it might be necessary to cut the middle bridge in the socket, to free space for C7.
3. Then small capacitors and small elco's.
4. Then all connectors, leds, fuse and dip-switch.
5. Before mounting VR1 AND VR2, first fix the cooling block with two screws.
6. After that place VR1 and VR2 in the pcboard, adjusting the wires in the right position, so that metal surface lies flat to the cooling and fix them with the clips.
7. Be sure that all IC's are flat to the surface of the cooling, cut the wires at the bottom at 1 mm outside the pcboard surface, and solder the wires.
8. Take a double check on the right types of VR1(LM2576t-12) and VR2(LM2575T-3.3)! They might sometimes be very hard to read.
9. At last fix bridge rectifier GR1 and C1,CE1.
10. Before inserting U1, U2 and U3, test power 3,3 Volt on pins 1 and 8 of U3.
11. Elco's C1 and CE1 have grown bigger , after production of the pcboard. Therefore, two extra holes are drilled to make CE1 fit better.
12. The picture above shows clearly that the wires of G1 are slightly bended, in order to clear space for C1. In case the total power consumption of the connected LocoNet is no more than 2 Amp, one of the two big capacitors can be omitted.
13. In the parts package, L3 is replaced by a ferrit toroid, with 7 windings.

The communication between Rocrail and the GCA101 is by the User Datagram Protocol. Therefor only the LNUDP LocoNet interface type is supported.
Setup Rocrail with the exact values shown below except for the Local IP address which is in most cases not needed.
The GCA101 own IP address is not used in the Rocrail setup.

This is the Multicast address to use for communication and must be set to the FIXED value of 224.0.0.1.
– The All Hosts multicast group addresses all hosts on the same network segment. –

The service port must be set to the FIXED value of 1235.

Only LNUDP is supported.

Only required if the PC has more then one network interfaces installed; In all other cases: Leave empty!
IP address of the PCs network interface which is used for communication with the GCA101 to make sure the traffic runs on the right one.

The link to a shopping list below contains most of the parts you need for this unit.
Please check the list carefully, we cannot be held responsible for the contents.
https://secure.reichelt.de/index.html?;ACTION=20;LA=5010;AWKID=539474;PROVID=2084