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Latest developments have proved that use of RC522 with 13,56 MHZ NFC is much cheaper to use.
Also, there very thin and cheap Tags available for this.
The used RC522 sensor boards a passive type so the need of an extra simple interface is required.
See for a more detailed descrioption at GCA41.



Tips for IDxx sensors

  • The displacement between RFID readers, ID-12LA, should be at least 30cm to be able to function.
  • The distance between reader and transponder is for small types critical; Create a test environment to test it to find out the best placement.
  • See for more information: Bi-Directional Communication.

Tips for GCA41 with RC522 RFID sensors

  • See GCA41 for more details.
  • In addition to installing the RC522 sensor right under the track, there is a small pcboard coil available from GCA.


Merg did a fine job in combining 8 RFID sensors attached to one board and from there read all sensors and send a completed number over the serial port to a PC.
This board is stepping a bit further by doing the same thing and in addition has CAN on board so the separate RS232 port is no longer needed.
The received numbers are simply send via the CAN BUS.

Allthought Rocrail can handle also the MERG RFID concentrator, connected to a serial or USB port, this CAN-GC4 is a bit more easy to connect.
To power all connectable 8 RFID sensors, the board needs a power supply of approx 0.25Amp at 5V.
For a linear regulator 5Volt , this is way too much for continuous functioning.
The CAN-GC4 steps down the 12 Volt as available in the CAN network by means of switching power supply.
It saves energy and also avoid hot parts on the board.

LEDs & Connectors



LED# Function Aspect Remark
1 CAN activity random flashing Depends on CAN traffic
2 Run continuos The board does not function if this LED does not illuminate
3 Learning mode 500ms blinking Activated by push button or Rocrail setup.
3 RFID checksum error or the ID is not in the list of allowed RFIDs. One shot flash


Name Function
Rf1-Rf8 RFID readers.
J4 Optional for current detection GCA93.
ICSP1 PIC Programmer.
J3 CAN BUS with 12V connection.
J1 CAN-GC connector out
J2 CAN-GC connector in

PSK header connectors




RFID sensors

CAN-GC4 RFID concentrator can connect up to 8 GCA41 with a RC522 each.

BK Column

The 8 block occupation detectors, GCA93, GCA94 or GCA173, can be assigned an address used for CAN BUS events.¹

Allowed RFID Column


Save RFIDs

Used for SoD; Use with care → Old information is reported!

Check RFIDs

The incoming RFID must be in the list of allowed RFIDs for generating a CAN BUS event.

Release RFIDs

An event with OPC_ASOF is send after 2 seconds to release the related sensor.

Accessory events instead of RFID events!!!

:!: No RFID event is generated if this option is active!

For use in combination with check RFIDs to trigger an output on the CAN-GC2.

¹) In Rocrail this is the sensor address.

RFID Notation

The RFID(Identifier) is formatted as dot-decimal notation with 5 parts:

Dot-Decimal Hexadecimal Decimal 0xFFFFFFFFFF 1099511627775

Rocrail server trace with activated monitor level:

20120328.181017.123 r9999c cbreader CAN BUS    0889 RFID short event 107 id=

See also: Loco code

RFID Readers

ID12/ID20 125 kHz RFID sensor

id-innovations.com_httpdocs_assets_immage_id12new.jpg This sensor Used by MERG has a type indication of "5 RFID". (3472+
Links :

Non of the recommended IDxx readers and tags can be ordered from GCA.

RC522 13,56 MHz RFID sensor (in combination with GCA41).

This unit has extended possibilities, compared with the IDxx types.
The most imporatant one is a better protection to distorsion from the running motor in the loc.
For description of GCA41 and RC552 RFID sensors please refer to GCA41
GCA41 (included pre-programmed Arduino Nano) and RC522 + tags are available from GCA.

can-gc4-en.txt · Last modified: 2022/02/06 14:16 by phg