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 /
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.
set03_03 connected to a Raspberry Pi using 3Bpi
Another view of set03_03
connected to a
Raspberry Pi using 3Bpi
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
set03_03 and set01_05_v3 boards translating USB to I2C :
Code used in this video
Using two I2C buses on Raspberry Pi :
Document revision :
20130730 - 2nd version: Updated July 30th, 2013.
- 1st version: Original document of April 25th, 2013 - www.electronics.cat