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+====== GCA174 DCC/Motorola decoder for GCA145 ======
+[[:english|{{  rocrail-logo-35.png}}]]
+[[:english|Content]] -> [[:hardware-en|Hardware]] -> [[:hardware-en#interfaces|GCA]]
+  *  [[:mgv-overview-en|The GCA modules]]
+ \\
+^^^^By Peter Giling ^^^^
+===== Direct decoder for Motorola or DCC =====
+This board is based on the design of digital-bahn.de.\\
+The firmware , copyright of Digital-Bahn.de, is available at http://www.digital-bahn.de/bau_led/led_schalten.htm#download\\
+This board is only attachable to J5 of GCA145/MGV145.\\
+It features the 7 outputs, needed to select position 1..48 on GC145/MGV145.\\
+Also an isolated feed-back is provided.\\
+Feed-back is free to be used with systems like S88.\\
+The on-board opto-couplers isolate the didital rail signals and feed-back from the board.\\
+Feed-back is very nice inside Rocrail environment, because it can signal Rocrail to start a train AFTER the selected postion has been reached.\\
+===== The prototype =====
+|   {{:gca:gca174_pict_02.jpg?600  }}  |  The board with opto-couplers \\ ready to be connected to GC145  |
+\\
+===== Hardware files of protoype =====
+{{:gca:gca174_sch.pdf|The schematics}}\\
+{{:gca:gca174_pcb.pdf|The pc-Board and parts positions}}\\
+{{:gca:gca174_parts.pdf|The bill of materials}}\\
+\\
+===== The final board design =====
+|  board in production, coming in short term  |
+\\
+===== Hardware files for final GCA174 design =====
+|  {{:gca:gca174final_sch.pdf|The schematic drawing}}  |
+|  {{:gca:gca174final_pcb.pdf|The pcb and parts positions}}  |
+|  {{:gca:gca174final_parts.pdf|The bill of materials}}  |
+\\
+===== Address selection =====
+Basicly, the firmware from Digital-bahn.de comes with adress  1..7.\\
+By pressing the button, the decoder is in learning mode, showing D1 to flash.\\
+All you have to do now, is sending the first address from your central unit.\\
+After that, just pwer off GCA145 and power on again.\\
+The addresses of the next ports will be automaticly set in following sequence\\
+One other option is to download hex_minipu from this page: http://www.digital-bahn.de/bau_pic/hexmanipu.htm#download .\\
+It will give you the option to directly change adresses and store them, before programming the chip.\\
+\\
+===== Feed-back =====
+GCA174 has a feed-back signal, to inform Rocrail that turntable is ready to move trains on/off.\\
+This feed-back signal is electrical (galvanic)isolated from the GCA174.\\
+By connecting J2 pt 1(-) and 2(+) to any device like S88 units or derivates,\\
+Rocrail will receive this port condition.\\
+Settings in Rocrail , see Position sensor
+===== Led signals =====
+GCA174 is priovided with 6 yellow leds for indication of decoded turntable position.\\
+The red led(D7) shows the write signal ( in Rocrail, look for 'new Position Flag' ), to inform GCA145 to start responding on the given position.\\
+\\
+===== Connections of GCA174 =====
+{{:gca:gca174_connections.pdf|}}
+===== Extra modification on GCA145(MGV145) =====
+GCA174 needs 5 Volt which is by default not available from J5 on GCA145.\\
+Therefore, this diode 1N4003 (or equivalent) should be mounted under J5 as this picture shows.\\
+**NOTE:** The latest green pcb has this diode(D10) on board, so no further attention needed.\\
+{{:mgv:hardware:extra-diode_on_gca145.jpg|}}
+\\