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+====== GCA_PI02  32 I/O I2C board for Raspberry Pi. ======
+[[english|{{  rocrail-logo-35.png}}]][[:rocnet:rocnetnode-en|{{ :rocnet:rocnet-hw.png}}]]
+[[english|Content]] -> [[hardware-en|Hardware]] -> [[hardware-en#rocnet_with_raspberry_pi|GCA-RasPi]]
+  * [[GCA1-PI01-en|GCA-PI01]] | [[:rocnet:pi01can-en|Pi01CAN]] | **[[GCA_PI02-en|GCA-PI02]]** | [[GCA-PI03-en|GCA-PI03]] | [[:gca-pi04-en|GCA-PI04]] | [[:gca-pi05-en|GCA-Pi05]] | [[:gca-pi06-en|GCA-Pi06]] | [[:GCA-PI07-en|GCA-PI07]] |  | [[:GCA-PI08-en|GCA-PI08]]  |  [[:gca107-en|GCA107 Relay board]] | [[:rocnet:rocdisplay-en|RocDisplay]] | [[:rocnet:fastclock-en|Fast Clock]]
+  * [[mgv-overview-en|The GCA modules]]
+  * [[:rocnet:rocnetnode-en|RocNetNode]]
+ \\
+^^^^By Peter Giling ^^^^
+[[http://raspberrypi.org|“Raspberry Pi" is a trademark of the Raspberry Pi Foundation.]]\\
+ \\
+===== The real thing =====
+|   {{:gca:gca_pi02_pict03.jpg?400}}  |
+|  A nice and easy to assemble board is available now.\\ No Surface Mount Devices (SMD) are used.  |
+===== Description. =====
+There is not really much to explain about this board.\\
+The two I2C lines, together with ground and +5V are all in the same connection cable.\\
+Two chips MCP23017 are used, each capable of adressing 16 I/O lines, thus 32 in total for 1 board.\\
+Of these boards can be linked together to one GCA_PI01, making 128 I/O lines available on 1 Raspberry PI.\\
+===== I2C system =====
+I2C is basicly made for communication between chips, together on one board.\\
+Therefore, according to specifications , the total length of all SDA and SCL wires together should not exceed 1 meter (3' 4'').\\
+This system will be made with addional line drivers, making a total length of 10 meters accessable.\\
+Each board is provided with an extra line driver P82B715 and a low drop voltage regulator to have 3.3 V available.\\
+The regulator skips the need of transporting 3.3 V from the Raspi, which could give more problems than profit.\\
+===== Address selection =====
+^  Board #  ^  dip1  ^  dip2  ^   I/O ports  ^ I2C Address ^
+|  1  |  OFF  |  OFF  |  1..32  |  0x20-0x21  |
+|  2  |  OFF  |  ON  |  33..64  |  0x22-0x23  |
+|  3  |  ON  |  OFF  |  65..96  |  0x24-0x25  |
+|  4  |  ON  |  ON  |  97..128  |  0x26-0x27  |
+===== Hardware =====
+====Boards/Kits====
+  * [[:gca:gca-index-en#raspbery_pi_rocnet_boards|Raspberry Pi Boards]]
+====Files====
+| {{:gca:gca_pi02_sch.pdf  |  The schematics}}  |
+| {{:gca:gca_pi02_pcb.pdf  |  The pc-board and parts positions}}  |
+| {{:gca:gca_pi02_parts.pdf | The partslist}} |
+^ N.B. Only complete ordered kits will be supported! ^
+ \\
+===== Cable connection. =====
+There are two possibilities for connection cable between the two boards.\\
+The choice is to use RJ45 connectors and Ethernet cable or RJ12 connectors, with the more flexible 6-wire cables, like known from Xpressnet and LocoNet.\\
+Maximum length of cable between GCA_PI01 and the last GCA_PI02 in the chain, (when line drivers are installed) is 10 meter.\\
+Without line-drivers, a maximum total length of 1 meter would be applicable.\\
+It is expected, nut not prooven yet, that Ethernet cable will handle slightly longer cable.\\
+This is all due to the specifactions of I2C.\\
+===== Power supply =====
+The GCA-PI02 needs 5Vdc.\\
+This 5V can be extracted from Raspberry Pi, if jumper JP1 on GCA-PI01 is set.\\
+If you prefer separate supply for this board, simply use a 5Volt (minimum 0,5A) USB power adapter.\\
+It connects to USB miniconnector V5.\\
+Also it is possible to supply 5 V from this board to Raspberry Pi, if you set jp1.\\
+In that case, do NOT connect 5V power to Raspberry.\\
+It works like this:
+The jumper on each GCA_PI01 and _PI02 board connects the 5Volt lines on board with the power line on the interconnection cable between the boards.\\
+In practice, use one 5V power adapter, and connect it with either one of the GCA_PI02 board USB connector, and \\
+set all jumpers on PI01 and PI02 boards, and the used 5V adaptor will supply all connected units.\\
+If you prefer separate 5V adaptors for each board, leave jumpers away.\\
+===== Pin configuration of ports =====
+^  Connector  ^   I/O 1  ^   I/O 2   ^  I/O 3  ^   I/O 4  ^
+|  Pin#  |  Port#  |  Port#  |  Port#   |  Port#   |
+|  1  |  x  |  x  |  x  |  x  | + 5V  |
+|  2  |  x  |  x  |  x  |  x  |  0V  |
+|  3  |  1  |  9  |  17  |  25  |
+|  4  |  2  |  10  |  18  |  26  |
+|  5  |  3  |  11  |  19  |  27  |
+|  6  |  4  |  12  |  20  |  28  |
+|  7  |  5  |  13  |  21  |  29  |
+|  8  |  6  |  14  |  22  |  30  |
+|  9  |  7  |  15  |  23  |  31  |
+|  10  |  8  |  16  |  24  |  32  |
+\\
+All I/O numbers are printed on the board itself.\\
+ \\
+===== Electrical limits =====
+Each port can be either source ( connect to 5 V ) or sink ( connect to 0V) of 25 mAmp.\\
+But the total current for each chip ( = 16 ports) is 125 mAmp. (source) or 150 mAmp. (sink).\\
+It is not allowed to source any power of any kind into the ports !\\
+====Relay board====
+Due to the limited current per unit from the 5V, only one relay board per I/O expander can be connected: \\
+On **I/O1** __or__ **I/O2** and on **I/O3** __or__ **I/O4**.\\
+ \\
+=====RJ12=====
+{{ :rocnet:rj12-pins.png}}
+^ Pin ^ Usage ^
+|  1  | VDD(+5V)|
+|  2  | SCL(B) |
+|  3  | VSS(GND) |
+|  4  | SDA (B) |
+|  5  | VSS(GND) |
+|  6  | VDD(+5V)|