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Digital Input / Output TWI (I2C) expander

Placa set03_03_v2

20130730www.electronics.cat



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Picture

set03_03_v02.jpg


Schematic

set03_03_v02_sch.png

Description


    
This board expands 16 inputs/outputs using TWI (I2C).

     Each board has two chips PCF8574. The lower bit is forced to a low level hardware (chip 1 A0 = 0 and chip 2 A0 = 1). Addresses A1 and A2 are set through SMD microswitch (SW1).

     The jumpers can notify if there is any change when reading, avoiding a constant reading of  I2C bus.

     P1 and P2 connectors are designed to be connected in daisy chain up to four set03_03 boards (64 inputs / outputs):

set03_03_v02_UsbTwi.jpg

set01_05_v03_uc.jpg

    P1 and P2 connect the bus TWI (aka I2C by its inventors, NXP). P3 and P4 connect input / output boards (ie : testing, relays and inputs).

     Power of this board comes from  its previous connected board.
 

set01_05_v03_Rpi.jpg
set03_03 connected to a Raspberry Pi using 3Bpi

set01_05_v03_Rpi.jpg
Another view of set03_03 connected to a Raspberry Pi using 3Bpi


set03_03_v02_UsbTwi02.jpg
set01_05_v3 connected to three expanders set03_03 with some peripherals

Video using Raspberry Pi and 3Bpi :


Code used in this video : twiDetect.c, twi01.c


Video using set03_03 and set01_05_v3 boards translating USB to I2C :


Code used in this video


Using two I2C buses on Raspberry Pi :





set03_03_v02_pcbSilk.jpg
set01_05_v01_pcbComp.png
set01_05_v01_pcbSold.png


Document revision :

20130730 - 2nd version: Updated July 30th, 2013.

20130425 - 1st version: Original document of April 25th, 2013 - www.electronics.cat