RPI i2c bus 16 I/O (mcp23017)

This guide shows how to get 16 I/O with 1 MCP23017 and a Raspberry pi - Here only used as output !!

PCS	Item	Calculated Price	Price bulk buy
1	MCP23017	2.49	E-bay US $ 2.49 with shipping to Denmark (July 2013)
16	220Ω Resistor	0.07	E-bay US $ 0,07 (@200 pcs US $ 0.91) with shipping to Denmark (July 2013)
16	LED 3 mm	0.15	E-bay US $ 0,15 (@500 pcs US $ 4.55) with shipping to Denmark (July 2013)

Recommended standard reusable hardware

PCS	Item	Calculated Price	Price bulk buy
1	Raspberry PI Type B and power	72,54	US $ 72.54 with shipping to Denmark (July 2013)
1	4 GB SD card	5.30	US $ 5.30 with shipping to Denmark (July 2013)
1	Wire Jumper Cable	7.49	US $ 7.49 with shipping to Denmark (July 2013)
3	BREADBOARD SYB-120 700 TIE-POINTS	5.67	E-bay US $ 5.67 (@1 pcs US $ 1.89) with shipping to Denmark (July 2013)

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Datasheet i2c 16-Bit I/O Expander (MCP23017)

Connect the circut, as shown. - If you what multible MCP23017, you shoot set the address, by pin 15, 16, 17

Start with prepare a Raspberry pi with supported os - my prefered is Raspbian “wheezy” Direct download my server (2013-05-25)

You can find my bref installation guide in RPI Info

■SSH into your Raspberry Pi
■Open the raspi-black-list.conf file using the following command : “sudo vi /etc/modprobe.d/raspi-blacklist.conf”
■Comment out the “blacklist i2c-bcm2708” entry by putting a hash # sign in front of it. So it looks like “#blacklist i2c-bcm2708”
■At this point you can also enable SPI device access by putting a hash # sign in front of “blacklist spi-bcm2708“.

■You then need to save your changes (:wq in vi) and reboot using the “sudo reboot” command.
■Now every time you reboot you will still need to perform two things to enable I2C:
■Type “sudo modprobe i2c-dev” and
■Type “sudo chmod o+rw /dev/i2c*“

Sample bash code for fast run !!