RPI-I2C-HUB

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I2C Hub/Repeater for the Raspberry Pi (RPI-I2C-HUB)

I2C-RPT-01 -6026 CCA-640px.jpg

Features

  • I2C Hub / Repeater / Replicator / Multiplexer / De-multiplexer
    • PCA9544A IC
    • Controlled via I2C
    • Multiple vendors
    • Devices with the same address can be attached to different ports
  • Host I2 port goes to Raspberry Pi I2C lines
    • 3.3V host operation
  • Four I2C slave ports
    • I2C ports can use the Raspberry Pi or have their own power (power source select jumper)
    • A Raspberry PI which runs 3.3V can control an I2C device which runs at 5V
  • Voltage translation between the ports
    • I2C ports can be 3.3V or 5V
  • Fits in any Raspberry Pi model
    • Cutout for Model B RCA video jack
  • Interrupt controller on each channel and host
  • 100KHz/400KHz operation
  • On-board termination resistors

Testing

  • PCA9544 Programming
  • Run with DigIO16-I2C card on Hub Port #0
  • Verify that the Hub is seen from the Raspberry Pi
  • Note should be -y 0 for the older revision Raspberry Pis
pi@raspi3 ~ $ sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- 71 -- -- -- -- -- --
  • Shows that there is an I2C part at 0x71
  • Next, set the mux to channel #0
pi@raspi3 ~ $ sudo i2cset -y 1 0x71 0x04 0x04
  • Verify that the hub is set to the port
pi@raspi3 ~ $ sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: 20 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- 71 -- -- -- -- -- --

Interrupts

  • (4) Active Low Inputs
    • 3.3K pullups
  • Active Low Output
    • 3.3K pullup
  • On Raspberry Pi GPIO_17
Each GPIO pin, when configured as a general-purpose input,
can be configured as an interrupt source to the ARM.

Power

  • Card power is 3.3V

Connectors

J1-J4 - I2C Slave ports 0-3

  1. GROUND
  2. Power (see H1-H4 for explanation)
  3. SDA
  4. SCK
  5. Interrupt*

H1-H4 - I2C power source selection

  • Installed - Raspberry Pi provides 3.3V power on the I2C connector power pin
  • Not installed - External device provides power on the I2C connector power pin

Code Examples

Factory Test

Test Setup

I2C-RPT-01-Demo01-512px.jpg

Test Steps

  • Hook up Raspberry Pi to Ethernet
  • Ethernet is using static IP
  • Connect (4) I2CIO-8 cards (Rev X2 or later add Interrupt line)
    • Set I2CIO-8 cards addresses to 000
    • Terminator jumpers not present
    • Use 5-pin 1:1 cables
  • Power up the Pi (using puTTY)
  • Verify all 4 I2CIO-8 cards have INT LEDs illuminated
  • Log onto Pi
  • Test code is here
  • Enter
cd ~/RasPi/RPI-I2C-Hub/R-Hub-Intr-4x8
sudo python R-Hub-Intr-4x8.py

  • Will cycle through the LEDs on all four cards
  • Insert/remove slowly (every 2 secs or so) shunts on input lines of I2CIO-8 cards
  • Int light will go out momentarily until message is displayed
  • Messages will be like
Input changed on channel 0 value = 0
Input changed on channel 0 value = 1
Input changed on channel 1 value = 0
Input changed on channel 1 value = 2
Input changed on channel 2 value = 0
Input changed on channel 2 value = 8
Input changed on channel 3 value = 0
Input changed on channel 3 value = 4
  • Verify all channels show input change (values do not matter)

Assembly Sheet

RPI-I2C-HUB Assembly Sheet

Checkout - Rev X1

  • Changed base address to 0x71
  • Added some extra pins marking